Categoria: elettronica

Wide Range R-C Oscillator TF 1370A, Serial N° 54110/053. Marconi Instruments Ltd. England.
Per ragioni indipendenti dalla nostra volontà per ora non possiamo accedere all’inventario dell’epoca, pur sapendo che si trova al n° 4025 ed è stato acquistato dopo l’esemplare  Serial N° 53336/08  e comunque nel 1966.
Il testo che segue è una parte del manuale di istruzioni custodito nell’archivio della Sezione Elettronica.
Una parte precedente del manuale è riportata nella scheda relativa al Wide Range R-C Oscillator TF 1370A, Serial N° 53336/08. Marconi Instruments Ltd. England. Per consultarla scrivere: “53336/08” su Cerca.
In rete il manuale di istruzioni è rinvenibile ai seguenti indirizzi:
https://ia800202.us.archive.org/35/items/marconi_tf1370a/tf1370a.pdf
http://bee.mif.pg.gda.pl/ciasteczkowypotwor/Marconi/tf1370a.pdf
Mentre una rivista nella quale vi è una interessante presentazione dello strumento si trova all’indirizzo: https://www.americanradiohistory.com/Archive-Marconi-Instrumentation/Marconi-1961-03.pdf
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«3 TECHNICAL DESCRIPTION
3.1 CIRCUIT ARRANGEMENTThe circuits of the Wide Range R-C Oscillator are selected and combined in a number of ways by the panel controls. The Functional Diagram, Fig. 3.1 shows how the circuits are employed. The basic oscillator is a Wien bridge type utilizing variable capacitance tuning and switched resistance range selection.
For sine-wave outputs up to 3.16 V, the basic oscillator output voltage is fed direct to a cathode follower output stage: for all other sine wave outputs up to 31.6 V, the oscillator output signal is applied to the output stage via an amplifier. Square wave signals are obtained from a Schmitt circuit, which is triggered by the amplified sine wave from the basic oscillator. Square waves from the Schmitt circuit are applied to the cathode follower output stage.
The output cathode follower feeds either the DIRECT output socket, or, via an attenuator or a 75 Ω resistor, the ATTEN output socket. The attenuator introduces 60 dB attenuation in six 10 dB steps and has a source impedance of 75 Ω. An output monitor measures the voltage at the input to the attenuator, or across a 300 Ω resistor when the attenuator is not in circuit. The front panel meter is calibrated to indicate either the source e.m.f. at the ATTEN output socket or the p. d. at the DIRECT output socket.3.2 OSCILLATOR
The basic oscillator, containing valves V1 to V4, is a Wien bridge type circuit. One arm of the bridge consists of a capacitor and a resistor in series, which are connected to a second arm consisting of a capacitor and a resistor in parallel.
The series connected capacitor and resistor include variable capacitor C10 and one of the fixed resistors, R1, R3, R5, R7, R9, or R11; the parallel connected combination contains variable capacitor C11 and one of the resistors, R2, R4, R6, R8, R10, or R12. A particular pair of resistors is selected by the RANGE switch, SA, for each of the six frequency ranges, and the variable capacitors, C10 and C11, are ganged to provide tuning over each range. Preset variable resistors and preset variable capacitors are included in the bridge arms to enable the end frequencies of each range to be accurately set.
The second pair of arms of the bridge consist of thermistor TH1 and resistor R29.
Out-of-balance voltage developed by the bridge is applied between the control grid of V3, via capacitor C20, and the cathode of V3, via the two cathode followers V1 and V2 in cascade. The output voltage of V3 is applied – via cathode follower V4 – directly across the bridge circuit, thus forming the bridge supply voltage, which is maintained constant by thermistor TH1 controlling the degree of negative feedback.
3.3 20 dB AMPLIFIER
At all settings of the OUTPUT VOLTS SELECTOR except that giving sine waves up to 3 V, the output signal from the oscillator circuit is fed to the control grid of valve V6 from the cathode of V4 via resistor R114 for square wave operation, or via the SET OUTPUT potentiometer for sine wave operation. The amplified signal from the anode of V6 is then taken either to the Schmitt trigger (V 5A and V5B) and thence to the output cathode follower, V7, for square wave output, or direct to V7 for DIRECT sine wave output.
When the RANGE switch is turned to ranges E or F for square wave output, or range F for DIRECT sine wave output the amplifier is rendered inoperative by removing the h. t. from V6. Simultaneously a voltage is applied to the WARNING CHECK RANGE neon indicator lamp. The necessary switching is effected by switch wafers SAk, Say, SAj and SCj.
3.4 SCHMITT TRIGGER
The output voltage from the 20 dB amplifier is fed to the control grid of V5A in the Schmitt trigger circuit when the OUTPUT VOLTS SELECTOR switch, SC, is turned to the first three clockwise positions, i.e., the SQUARE, 3, 10, or 30 settings.
The Schmitt circuit, containing the two triode sections V5A and B, is triggered by the sine wave output signal from the 20 dB amplifier. One triode is held conducting while the other triode is non-conducting; the polarity of the sine wave signal applied to the control grid of the first triode section, V5A, decides which one of the two sections is conducting at any instant. To enable the switching of condition to occur at the precise base line of the sine wave input voltage, the control grid of V5A is biased by a voltage obtained from the slider of the M/S potentiometer, RV9, which is a preset control accessible at the front panel. The grid of V5A is d. c. coupled to the anode of V6; R83, the anode load of V6, forms part of the resistance chain from which the grid bias of V5A is obtained.
Preset capacitor C28, connected between the anode of V5A and the grid of V5B, is included to improve the frequency response of the coupling circuit, and is set for the best rise time. Capacitor C59, connected between the grids of the two triode sections, bucks out any curvature on the negative excursions of the square wave output signal, particularly at the higher frequencies.
The output from the Schmitt trigger circuit is fed from the anode of V5B to the grid of cathode follower V7, in the output stage, via switch SCe, capacitor C30, and resistor R49. The amplitude of the signal is controlled by varying the value of the anode load of VBB; this is achieved by variable resistor RV8A and resistor R46.
The rise time of the signal at the anode of the second triode, V5B, depends upon the value of its anode load, and reduces proportionately with the output level; so for the best performance, the amplitude of the signal should be adjusted for a front panel meter reading of about 1/3 of f.s.d.
Potentiometer RV8A is mechanically ganged to RV8B in the oscillator circuit, and the combined potentiometers function as the SET OUTPUT control.
The preset SAG control on the front panel, RV10, adjusts the flatness of the horizontal part of the output signal waveform.
This correction, mainly necessary below 100 c/s, is achieved by introducing into the waveform some curvature in opposition to the sag caused by the coupling capacitors following the Schmitt circuit. The correcting circuit consists of capacitor C32, resistor R46, a part of the SET OUTPUT control RV8A according to its setting, and variable resistor RV10. The inclusion of RV8A in the SAG control circuit ensures that the horizontal flatness of the waveform is largely independent of the SET OUTPUT control setting, particularly for outputs up to 1/3 of full-scale front-panel meter indication.

3.5 OUTPUT CATHODE FOLLOWER
The output voltage from the basic oscillator, the 20 dB amplifier, or the
Schmitt trigger circuit, is fed to the control-grid of output cathode follower V7, depending upon the setting of the OUTPUT VOLTS SELECTOR switch, SC.
The shunt-compensated cathode follower output stage contains two pentodes, V7 and V8, connected in series. The lower pentode, V8, is triode connected and forms the cathode load of the upper pentode, V7. The signal voltage developed across resistor R50 in the anode circuit of V7, is fed via capacitor C35 to the control grid of V8, thus supplementing the output signal at the cathode of V7. The output stage introduces only an extremely small amount of distortion and has an output impedance of about 15 Ω.
The signal voltage is taken from the cathode of VT and feeds the DIRECT or the ATTEN output socket via the output attenuation networks, according to the position of the OUTPUT VOLTS SELECTOR switch.
3.6 OUTPUT MONITOR
The output monitor circuit, containing meter M1 and diodes MR1 and MR2, functions as a push-pull mean—Reading rectifier circuit fed via cathode follower V9. The meter scale is calibrated in r.m.s. values for sine waves and peak readings for square waves. Resistor R81 is connected in circuit when measuring square wave voltages and is short circuited for sine wave measurements, the circuit having a. greater sensitivity to square wave inputs.
Potentiometer RV11 connected in series with the meter sets the sensitivity of the meter. Capacitors C43 and C44 provide the necessary a.c. path for the rectifying diodes, and in addition C44 prevents d.c. flowing between the positive cathode of V9 and earth via diode MR1 and the meter. Capacitor C45 is included in the circuit to reduce the d.c. leakage current in capacitor C44, which would normally affect the meter indication. C45 charges up through resistor R60 to near the potential of the cathode of V9, leaving only a. small d.c. polarizing potential across capacitors C43 and C44. Capacitors C66 and C67 function as by-pass capacitors. They prevent any r.f. currents, which may be induced in the connecting leads, from passing through the meter.
3.7 OUTPUT CONNECTIONS
Output from the cathode follower V7 is fed to either the DIRECT or the ATTEN output socket via attenuation and impedance adjusting networks, arranged according to the position of the OUTPUT VOLTS SELECT OR switch, SC, as follows:
(1) SINE or SQUARE, 30 DIRECT:
Output from V7 is fed via C36 and C37, and switch SC, to the DIRECT output socket at a source impedance of 25 Ω. The output monitor measures one tenth of the output voltage, i. e. , measures the voltage appearing across the 300 Ω input impedance to the step attenuator circuit (or the 300 Ω resistor R59) that is connected in series with R64 and R65. The meter calibration on the lower scale, 0-31.6 V, indicates the actual voltage at the DIRECT output socket.
 (2) SINE, or SQUARE, 10 DIRECT:
Output from V7 is fed via C36 and C37, and switch SC, to resistor R64. The signal output is taken from the junction R64/R65 and is one third of the voltage from the cathode of V7. The source impedance is 650 Ω. The output monitor measures one tenth of the voltage from V7, i. e. , measures the voltage appearing across the 300 Ω input impedance to the attenuator circuit (or the 300 Ω resistor R59) that is connected in series with R64 and R65. The meter calibration on the centre scale, 0 -10 V, indicates the actual voltage at the DIRECT output socket.SINE, 3 ATTEN:
Output from V7 is applied via C36 and C37 to the step attenuator network feeding the ATTEN outlet. The attenuator network includes a chain of six 10 dB sections, which are progressively withdrawn as the ATTENUATED OUTPUT switch, SB, is turned clockwise. At the seventh position, 3 V, SB substitutes a 75 Ω series resistor, R68.
Source impedance at the ATTEN outlet is selected by the ATTEN IMPEDANCE switch SE. When this is set to 75 Ω, the source impedance is the 75 Ω output impedance presented by the stages of the step attenuator except that, if SB is set to 3 V, the 75 Ω  series resistor combines with the output impedance of V7 giving a true source impedance of approximately 100 Ω at the outlet.
Turning the ATTEN IMPEDANCE switch to 100, 130 and 600 Ω adds R119, 25 Ω, R98, 30 Ω and R82, 470 Ω, cumulatively in series with the ATTEN outlet.
The output monitor measures the voltage from V7 and indicates the source e.m.f. in series with the selected source impedance. The meter scales should be read in conjunction with the setting of SB. When SB is set to 3 V, since the monitor indicates the voltage at the point where V7 feeds the 75 K2 series resistor, it therefore indicates the e.m.f. at the selected nominal source impedance, excluding the output impedance of V7.
R59 ensures a. leakage path for the electrolytic capacitor C36 if a. load is not connected when SB is in the 3 V position.(4) SQUARE, 3 ATTEN:
The output circuit arrangement is the same as that described for SINE, 3 ATTEN, except that the step attenuator network receives its input from C36 and C37 via. R64 and R65. The long CR time constant provided by this path is necessary to avoid sag of the square wave. However, the presence of R64 and R65 has the effect of raising the true source impedance at the ATTEN outlet as the ATTENUATED OUTPUT switch, SB, is turned to positions of high output (see Table 2.1 in section 2. 6).
The output monitor measures the voltage at the 300 Ω input of the attenuator chain (or across R59) and indicates the source e.m.f. in series with the selected nominal source impedance, excluding R64, R65, and the output impedance of V7.3.8 REGULATED H.T. SUPPLY
The power unit, containing valves V10 to V14, supplies an unregulated 400 V to the output cathode follower and a regulated 285 V to the remaining stages in the instrument.
Double triode V11 has its two sections connected in parallel and functions as a series regulator. The shunt amplifier that controls V11 includes double triodes V12 and V13. The error voltage input to this amplifier is the difference between (i) a fraction of the h.t. potential, obtained from the slider of the potentiometer RV12, and (ii) the reference potential developed by stabilizer V14. These two potentials are individually applied to the grids of the two cathode coupled triodes of V13. Any change of h.t. potential applied via RV12 to V13 is reinforced by the other half of V13, which draws its anode current from the resistor chain feeding RV12. The half of V13 to which RV12 is connected is coupled  to  the cathode of  V12B in a cascade arrangement.
The amplified error voltage appearing across resistor R100 in the anode circuit of V12B is fed via cathode follower V12A to the control grids of series regulator V11.3.9 REGULATED L.T. SUPPLY
The 1.t. d.c. to the basic oscillator, V1 to V4, is provided by the regulated 1.t. supply.
Secondary winding LT3 on mains transformer T 1 supplies 11 V  d.c. via bi-phase rectifier MR3 (A and B), at nominal mains input.
Transistors VT1, VT2 and VT3 form a stabilizer circuit consisting of an amplifier, an emitter follower and a series regulator. Part of the output voltage, taken via RV15, is compared by the amplifier with a. reference voltage provided by a Zener diode, MR8. The resultant error signal is fed to the base of the series regulator, VT3, by the emitter follower, thereby controlling VT3 and keeping the output voltage constant.
Preset potentiometer RV15 is set to give an output voltage of 6.3 V.»
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Wide Range R-C Oscillator TF 1370A, Serial N° 53336/08. Marconi Instruments Ltd. England.
Per ragioni indipendenti dalla nostra volontà per ora non possiamo accedere all’inventario dell’epoca, pur sapendo che si trova al n° 4002 ed è stato acquistato poco dopo il 17 gennaio 1966 (osservare il timbro in alto a destra).Riportiamo qui una prima parte del manuale di istruzioni custodito nell’archivio della Sezione Elettronica.

Una parte successiva del manuale è riportata nella scheda relativa al Wide Range R-C Oscillator TF 1370°, Serial N° 54110/053. Marconi Instruments Ltd. England. Per consultarla scrivere: “54110/053” su Cerca.
In rete il manuale di istruzioni è rinvenibile ai seguenti indirizzi:
https://ia800202.us.archive.org/35/items/marconi_tf1370a/tf1370a.pdf
http://bee.mif.pg.gda.pl/ciasteczkowypotwor/Marconi/tf1370a.pdf
Mentre una rivista nella quale vi è una interessante presentazione dello strumento si trova all’indirizzo: https://www.americanradiohistory.com/Archive-Marconi-Instrumentation/Marconi-1961-03.pdf
§§§ «1 GENERAL INFORMATION
1.1 FEATURES
The TF 1370A is a general-purpose sine wave generator covering the frequency range 10 c/s to 10 Mc/s. It also delivers a high-quality  square wave output at frequencies between 10 c/s and 100 kc/s.
The instrument is primarily a signal  source for measurements and tests on audio and video amplifiers and networks. With its four output impedances – 600, 130, 100, and 75 Ω – it is suitable for use with transmission lines, filters, attenuators, etc.
Among other applications as a sine wave generator is that of providing the excitation voltage for a. f. and r. f. bridges. And the quality of the square wave output also renders the instrument particularly effective for such purposes as rapid testing of audio amplifier bandwidth.
The signal originates in a Wien bridge oscillator covering 10 c/s to 10 Mc/s in six decade bands, the top band extending from 1 to 10 Mc/s. A single scale is used for the four lower bands and separate scales for the two upper bands; this gives a total scale length of 105 inches and makes a 1% change in frequency easily discernible. Speed and precision of tuning are reconciled by a dual-ratio control, 3:1 for rapid adjustment and 18:1 for fine tuning.
TF 1370AR is a rack-mounting version of the TF 1370A and is supplied, complete with dust cover, for mounting in a standard 19 inch rack.1.2 DATA SUMMARY
FREQUENCY
Range : Sine waves : 10 c/s to 10 Mc/s in six decade bands. Square waves; 10 c/s to 100 kc/s in four decade bands.
Accuracy : Within ±2%  ±1 c/s.
Stability: Drift does not exceed :0. 1% Over a 15 minute period after 1 hour warm-up.
SINE WAVE OUTPUT
Range (via attenuator): 1 mV to 3.16 V e.m.f. at switch selected source impedances of 75, 100, 130 and 600 Ω unbalanced. Controlled by attenuator with six 10 dB steps and potentiometer in conjunction with level monitor.
Attenuator accuracy is ±1 dB overall on resistive load.
Outputs from 10 µV to 31.6 mV at 75 and 5 Q are available by using ×100 Attenuator Pad TM 6454.
Range (direct): Up to 31.6 V p.d. across loads of 2.2 KΩ or greater, at frequencies up to 1 Mc/s. Two ranges of up to 10 and 31.6 V are provided by switched potential divider and potentiometer in conjunction with level monitor.
Nominal impedances are 650 Ω on 10 V range, and 25 Ω in series with 500 µF on 31.6 V range.
Frequency response (via attenuator and without adjusting meter):
Relative to 1 kc/s
Within ±0.25 B from 100 c/ to 1Mc/s.
Within ±0.5 dB from 10 c/s to 100 c/s.
Within ±1 dB from 1 Mc/s to 10 Mc/s.
Distortion factor :
3 V output level
Less than :
2% from 20 c/s to 100 c/s
0.5% from 100 c/s to 100 kc/s
1% from 100 kc/s to 1 Mc/s
2% from 1 Mc/s to 4 Mc/s
5% from 4 Mc/s to 10 Mc/s
30 V output level
Less than:
2% from 20 c/s to 100 c/s
1% from 100 c/s to 100 kc/s
2% from 100 kc/s to 1Mc/s
Hum: Less than 0. 1% of ful1—scale output above 10 mV.
SQUARE WAVE OUTPUT
Range: 1 mV to 3.16 V peak via attenuator, and up to 31.6 V peak direct.
Other details as for sine wave output except that source impedance is increased by 250 Ω at maximum output step of attenuator.
Frequency response (without adjusting meter):
Relative to 1kc/s
Within:0. 3 dB from 10 c/s to 100 kc/s.
Rise time:
0.75 µsec or less at ful1-sca1e output.
0.4 µsec or less at 1/3 full-scale output.
Sag:  Approximately 5% in a. 2.2 kΩ load at 20 c/s.
Adjustable by panel preset.
Mark/space ratio: 50/50 ±5%. Adjustable by panel preset.
LEVEL MONITOR
Voltage scales : 0 to 31. 6 and 0 to 10; indicate r.m.s. value of sine wave and peak value of square wave with respect to zero.
Decibel scales : 0 to -20 with respect to full-scale; also 0 dB reference point indicating 1 V peak to peak sine wave or square wave across a 75 Ω load.
Accuracy: ±3% of full-scale for sine waves up to 1 Mc/s; additional ±2% of reading for square waves, and for sine waves up to 10 Mc/s.
POWER SUPPLY: 200 to 250 V and 100 to 150 V, 45 to 65 c/s, 150 W.
DIMENSIONS & WEIGHT :
Height  14 in (36 cm) Width 20 in (51 cm) Depth 11 in (Z8 cm) Weight as lb (17 kg)
1.3 ACCESSORIES
Accessories supplied
One coaxial free plug, type BNC, Transradio Cat. No. BN1/7 (75 Ω); for DIRECT or ATTEN output connections.
Accessories available  
(1) UNBALANCED—TO—BALANCED TRANSFORMER
TYPE TM 6221
This transformer provides balanced signals at 600, 200, or 150 Ω source impedance, and is for use with sine wave outputs in a frequency range 10 c/s to 100 kc/s.
Connections: BNC socket for input; terminals for outputs, centre-tap, and earth.
Impedance ratios: 600 Ω to 600, 200, and 150 Ω.
Insertion loss (at 1 kc/s] : 0.5 dB approximately.
Out-of-balance: Not exceeding 0.2 dB from 150 c/s to 50 kc/s; not exceeding 1 dB at 20 c/s or 100 kc/s.
Response at secondary (with respect to 1 kc/s): ±0. 2 dB from 150 c/s to 50 kc/s; not below -1 dB at 2.0 c/s or 100 kc/s.
Distortion factor: ( loaded and fed by a pure sine wave at 3 V e.m.f.):  100 c/s to 50 kc/s, not exceeding 0.2%; 70  c/s to 100 c/s and 50 kc/s to 100 kc/s, not exceeding 0.4%.
Dimensions & weight : Height  3 ¼ in (8.5 cm) Width  4 ⅞ in (12.5 cm) Depth 4 in (10.5 cm) Weight  2 ¼ lb (1.1 kg)(2) 1 kc/s BAND-PASS FILTER TYPE TM 6222
This device. in series with the instrument, passes a pure 1 kc/s signal for applications requiring a very pure waveform.
Connections : Input, BNC socket; output, terminals
Impedance : 600 Ω  ±10% when terminated by 600 Ω.
Insertion loss (at optimum pass frequency) : Not exceeding 1 dB. 3 dB Pass band: ±90 c/s approximately.
Distortion factor (loaded and fed by TF 1370A): Not exceeding 0.02%, feeding 250 mV to load; not exceeding 0.1% feeding 1 V to load.
Dimensions & weight: Height 3 ¼ in (8.5 cm) Width 4 ⅞ in (12.5 cm) Depth 4in (10.5 cm) Weight 2 ¼  lb (1.1 kg)

(3) ×100 ATTENUATOR PAD TYPE TM 6454
This device enables reduced outputs to be obtained down to 10 µV at a source impedance of 5 Ω or 75 Ω, and is for use with sine wave or square wave signals at all operating frequencies of the R—C Oscillator.
Connections : Three BNC sockets.
Loss : 40 dB  ±1 dB.
Impedance : Input, 75 Ω; outputs, 75 and 5 Ω.
Maximum input : 6 V.
Dimensions & weight : Height  1 in (3 cm) Width 3 ¾ in (9.5 cm) Depth 1 ⅞ in (5 cm) Weight 4 oz (120 gm)
(4) COAXIAL LEAD TYPE TM 4726/136
Primarily intended for connecting (1), (2) or (3) above to the output sockets of the Oscillator.
Connections: BNC plug at each end.
Impedance: T5 Ω.
Length: 36 inches.
2 OPERATION
2.1 INSTALLATION
The instrument is normally dispatched ready for a 240 V supply unless otherwise ordered. Before switching on be sure that the connections on the mains transformer are correct for the supply voltage to be used – see Section 4.3. If the instrument is supplied in a plastic cover, completely remove this to ensure adequate ventilation.
2.2 SWITCHING  ON
Connect the power lead to the a. c. supply socket; when not in use this lead is stowed in the left-hand case handle recess. Switch ON the SUPPLY switch. The red pilot lamp should glow.
Allow several minutes to elapse for the instrument to warm up. But allow longer, say an hour, when the highest stability is required.
2.3 SINE AND SQUARE WAVE OUTPUTS
Sine wave
Outputs from 1 mV to 3.16 V are available via a switched attenuator covering 60 dB in 10 dB steps. The signal level applied to the input of the attenuator is continuously variable and is monitored by a meter calibrated in open circuit voltage and decibels.
The output impedance can be set to 75, 100, 130, or 600 Ω , as required.
Low outputs down to 10 µV at 75 or 5 Ω can be obtained by using the ×100 Attenuator Pad available as an optional accessory.
High outputs up to 31.6 V, at frequencies up to 1 Mc/s, are delivered at a separate outlet; this outlet is controlled by a switched potential divider with a continuously variable input, and the meter indicates the voltage across the load. Switching to a higher frequency band during high output operation automatically lights a warning lamp to show that this is not an operative condition.
Square wave
Square Wave outputs up to 31.6 V peak are available at frequencies up to 100 kc/s. The warning lamp facility provided for high output sine wave operation also applies for square waves if a higher frequency band is selected. Output arrangements are similar to those for sine waves except that the meter indicates the peak amplitude with respect to zero, i. e. , half the peak-to-peak voltage.
Both sag and mark/space ratio are adjustable by front panel presets. Below 50 c/s, the sag can be adjusted to zero for any particular load; above 50 c/s, one zero setting is valid for all loads. The mark/space preset enables the ratio to be brought exactly to 50/50.
2.4 CONTROLS AND CONNECTORS
1.SUPPLY switch and indicator lamp.
2.RANGE selector. Letters refer to scales on the dial, and numbers indicate the scale extremes. Illustration shows setting for 1 kc/s.
3.FREQUENCY control. Combined two-ratio drive allowing quick coarse adjustment, then fine tuning over one turn of the knob.
4.FREQUENCY dial. Use scale indicated by setting of RANGE selector.
5.OUTPUT VOLTS selector. Selects sine wave or square wave operation, and output range at ATTEN or DIRECT output sockets. OFF position disconnects output without interrupting supplies.
6.SET OUTPUT control. Adjusts output voltage at ATTEN or DIRECT output sockets.
7.METER. Shows output at either ATTEN or DIRECT socket depending on settings of OUTPUT VOLTS SELECTOR and AT TENUATED OUTPUT switch. Indicates peak value of square waves and r. m. s. value of sine waves. SQ and SINE marks correspond to 1 V peak-to-pea.k in a. 75 Ω load.
8.ATTENUATED OUTPUT switch. Setting indicates full-scale meter deflection.
9.ATTEN IMPEDANCE switch. Indicates source impedance at ATTEN outputsocket on ‘mV’ settings of ATTENUATED OUTPUT switch. OFF position disconnects output without interrupting supplies.
10.ATTEN  E.M.F. socket. Type ENC. For outputs up to 3.16 V. 11.DIRECT OUTPUT socket. Type BNC. For outputs up to 31.6 V. 12.WARNING CHECK RANGE lamp. Glows when an inadmissible combination of output range and frequency has been selected.
13.M/S preset. For fine adjustment of square wave mark] space ratio.
14.SAG preset. For zeroing square wave sag.2.5 ADJUSTING FREQUENCY
Turn the RANGE switch to select the frequency band and adjust the FREQUENCY tuning control for the required frequency.
The FREQUENCY tuning control has a combined two-ratio drive, allowing quick adjustment to approximately the required frequency, then fine tuning (over one turn of the knob) through the region of the required frequency.
2.6 SETTING OUTPUT VOLTAGE
Turn the OUTPUT VOLTS SELECTOR switch to the appropriate position for the output required. The settings of this switch for the various output conditions available are shown in Table 2.1.
Notes:
(i) If the OUTPUT VOLTS SELECTOR is set to any of the DIRECT positions and the RANGE selector is switched to above 1 Mc/s for sine waves, or above 100 kc/s for square waves, no output can be obtained. In this condition the WARNING CHECK RANGE lamp will glow.
(ii) The OFF position enables you to remove the output without switching off the supply or disconnecting the load.CAUTION
D.C. content in output. The output coupling capacitor in the R-C Oscillator is, of necessity, a high capacitance electrolytic type. This allows some cl.c leakage which may affect equipment connected to either outlet. The leakage voltage may amount to some 2% of the a. c. output, both at the DIRECT outlet when loaded with 2 kΩ, and at the ATTEN outlet when matched with 75 Ω .
Surges in output. When switching the SUPPLY on or off, and when turning the OUTPUT VOLTS SELECTOR, d.c. surges lasting several seconds arise at the outlets. Depending on the switching operation, the surge open circuit voltage may be up to about twenty times the a. c. output provided by the settings of the SELECTOR and ATTENUATED OUTPUT switches.
The output of the R-C Oscillator should be open or short circuited temporarily when the load is sensitive and might be damaged.
Direct output, up to 30 V
From the DIRECT output socket a sine wave or square wave of up to 10 V or up to 31.6 V can be obtained, depending on the position of the OUTPUT VOLTS SELECTOR and the SET OUTPUT control.The meter, calibrated in peak values for square wave and r.m.s. for sine wave signals, indicates the voltage across the load at the DIRECT outlet; this voltage is adjusted by the SET OUTPUT control. The source impedance on the 10 V range is 650 Ω, and on the 30 V range it is 2.5 Ω in series with 500 µF. The permissible external loads are shown in Table 2.1.
As a rule, when a. square wave is taken from the DIRECT outlet, a short output cable should be used; a long cable may cause rounding of the square wave owing to loss of higher frequency components.
While the SELECTOR is at a DIRECT position output can be taken simultaneously from the ATTEN socket. But if the ATTENUATED OUTPUT switch is set to the 1 V or 3 V positions and the ATTEN outlet is loaded, the meter will indicate incorrectly the voltage at the DIRECT outlet. The output impedance at the ATTEN socket will be as for SQUARE ATTEN (see Table 2.1) for both sine and square waves.
Attenuated output, 0 to 3 V
When the OUTPUT VOLTS SELECTOR switch is turned to the SQUARE, 3 ATTEN or SINE, 3 ATTEN positions, the meter and the ATTENUATED OUTPUT switch together indicate the source e.m.f. , i. e. the open circuit voltage at the AT TEN output socket.
The seven position ATTENUATED OUTPUT switch provides one +10 dB and five -10 dB steps, relative to the 0 dB position. According to the voltage required, the ATTENUATED OUTPUT switch should be set to the appropriate position. The voltage indicated by each switch position is the maximum e.m.f. obtainable and also the full-scale meter indication for this switch position; depending upon whether the switch position figure commences with 1 or 3, the 10 V or 30 V scale of the meter should be referred to and the appropriate multiplying factor applied.Examples:
(i) If 80 mV is required, turn the ATTENUATED OUTPUT switch to 100 mV, and adjust the SET OUTPUT control to obtain a reading of B on the 10 V meter scale.
(ii) If 240 mV is required, turn the ATTENUATED OUTPUT switch to 300 mV, and adjust the SET OUTPUT control to obtain a reading of 24 on the 30 V meter scale.
Turn the ATTEN IMPEDANCE switch to give the source impedance required.
When using sine wave outputs above 500 kc/s, it is recommended that there should be good matching between the instrument, output lead, and load, i. e., the ATTEN IMPEDANCE setting, the characteristic impedance of the output cable, and the impedance of the load should all have the same value. If the output cable is not matched above 500 kc/s, it may introduce a reactive component in the coupling that will modify the output actually obtained at the load. The effect increases with length of cable.
Example :
With the ATTEN IMPEDANCE switch turned to 600 Ω and using a 3 ft, 75 Ω, coaxial lead to connect a 600 Ω load to the instrument, the output voltage will be reduced by above 0.15 dB at 500 kc/s, and about 3 dB at 7 Mc/s.
It should be noted that it is not possible to obtain a zero meter reading when using square wave signals.
The rise time of the square wave signal is reduced proportionately with its output amplitude. So, for the shortest rise time, it is preferable to set the ATTENUATED OUTPUT switch so that the SET OUTPUT control can be adjusted to give the required output at a low meter reading. Further, to retain the shape of the square wave, try to obtain good matching between the instrument, output cable and load as recommended above for sine waves over 500 kc/s. (Note that the true source impedance is increased if the ATTENUATED OUTPUT switch is set to 1 V or 3 V — see Table 2.1.) If it is not convenient to obtain good matching, the output cable should be kept short; say 3 feet or less. Failure to match a longer cable may cause loss in the higher frequency components of the square wave and result in rounding of its shape.2.7 dB READINGS
Reading relative dB levels
The top scale of the front panel meter is calibrated in dB relative to full-scale meter deflection. Changes of voltage reading on the meter scale may therefore be read in decibels by simply subtracting a lower level from a higher level.
When the ATTENUAT ED OUT PUT switch position is changed, each increment of 10 dB must be added to the relative meter indication obtained. Note any change of meter reading as the switch is turned, and reset the SET OUTPUT control if necessary (in particular, switching to +10 dB only increases square waves by 10 dB if the level indicated by the meter can be maintained.)
Examples:
(a) The meter is first reading 800 mV, corresponding to -2. dB on the scale (with the ATTENUATED OUTPUT switch turned to 1 V). The output is then reduced to give a meter reading of 400 mV, corresponding to -8 dB on the scale. The signal reduction is given by the difference between the two dB readings, i.e., (-2) – (-8) = 6 dB signal reduction.
(b) The meter is first reading 800 mV, corresponding to -2 dB on the scale with the ATTENUATED OUTPUT switch turned to 1 V. 0 dB. The output is then reduced to give a meter reading of 40 mV, corresponding to -8 dB on the scale, with the switch turned (through 20 dB) to 100 mV, – 20 dB. The signal reduction is given by the difference between the two dB indications, e. g. , (-2) – [(-20) + (-8)] = 26 dB.
Using standard video ref level
Included on the top scale of the front panel meter are two calibration marks, SQ and SINE, indicating the standard level of 1 V peak-to-peak in a. 75 Ω load (corresponding to 1 V peak e.m.f. at 75 Ω source impedance).
To obtain this level, set the ATTEN IMPEDANCE switch to 75 Ω, set the ATTENUATED OUTPUT switch to 0 dB (1 V), and adjust the SET OUTPUT control to obtain a meter deflection to the SQ or SINE mark on scale according to whether a square or a sine wave output is required from the ATTEN output socket. The standard level will then appear across the 75 Ω load.
If, for example, a signal 7 dB below the standard level is required, adjust the SET OUTPUT control to reduce the meter deflection by 7 dB as read on the meter dB scale (i. e. , down to -7 dB for a square wave output, or to -10 dB for a sine wave output).
2.8 SETTING UP AUDIO STANDARD OUTPUT
If a sine wave source is required at the audio standard of 1 mW in 600 Ω, or levels at 10 dB or 20 dB above the standard, proceed as follows:
1 mW (0 dBm) in 600 Ω
(i) Connect the external equipment to the ATTEN output socket.
(ii) Turn the OUTPUT VOLTS SELECTOR switch to SINE, 3 ATTEN.
(iii) Turn the ATTEN IMPEDANCE switch to 600 Ω.
(iv) Turn the ATTENUATED OUTPUT switch to 3 V.
(v) Adjust the SET OUTPUT control to give a meter reading of 1. 55 V. (The meter indicates the e.m.f. at 600 Ω source impedance.)
10 mW (+10 dBm) in 600 Ω
(i) Connect the external equipment, via a 600 Ω resistor, to the DIRECT output socket.
(ii) Turn the OUTPUT VOLTS SELECTOR switch to SINE, so DIRECT.
(iii) Adjust the SET OUTPUT control to give a meter reading of 4.9 V. (The meter indicates the e.m.f. at 600 Ω source impedance.)
100 mW (+10 dBm) in 600 Ω
(i) Connect the external equipment, via a 600 Ω resistor, to the DIRECT output socket.
(ii) Turn the OUTPUT VOLTS SELECTOR switch to SINE, 30 DIRECT .
(iii) Adjust the SET OUTPUT control to give a meter reading of 15.5 V. (The meter indicates the e.m.f. at 600 Ω source impedance.)
Note : As the instrument load under these conditions is 1200 Ω, it is not advisable to obtain a meter reading greater than about 20 V, otherwise distortion will occur. The normal minimum load is 2 kΩ (see Table 2.1).

2.9 ADJUSTING SQUARE WAVE SAG AND MARK/SPACE RATIO
The SAG preset control on the front panel enables you to make readjustments, below about 100 c/s, to minimize the sag on the horizontal top and bottom of the square wave at any particular signal level and load conditions that comply with Table 2. l.
To make an adjustment proceed as follows:
(1) Connect the load to the instrument and set the controls to give the required signal output.
(2) Connect an oscilloscope, having a flat response down to d. c. and an input impedance that is large compared with the load, so as to monitor the square wave signal.
(3) Adjust the SAG preset control to give zero sag of the waveform viewed on the oscilloscope.
Note: At other conditions of load, frequency, and signal amplitude to those used above, there will be a. variation in performance, and the SAG control should be reset as described in section 4. 7. 2 in order to restore the instrument to the standard condition.
Mark/space ratio
The M/S preset control on the front panel enables you to readjust the mark/space ratio of the square wave signal to exactly 50/50 at a particular frequency.
To make an adjustment, proceed as follows:
(1) Set the controls of the instrument to give the required frequency.
(2) Connect an oscilloscope, having a response that is flat from d. c. to 1 Mc/s, so as to monitor the output signal.
(3) Adjust the M/S preset control to give exactly the required mark space ratio of the square wave, viewed on the oscilloscope.
Note : To restore the instrument to the standard condition, see section 4. 7. 1.2.10 USE OF ACCESSORIES
Unbalanced-to-Balanced Transformer Type TM 6221
The transformer is for use with sine wave signals between 10 c/s and 100 kc/s, fed from a 600 Ω source. It provides balanced outputs at an impedance of 150, 200, and 600 Ω and has a centre-tapped secondary winding.An output may be taken from one half of the various secondary windings, i. e. , from one terminal of a pair and the centre tap. In these cases, the output impedance will be one quarter of the impedance marked at a particular terminal. The high frequency response may be slightly worsened.
Example :
If an output is taken from one 200 Ω terminal and the C. T. terminal, the
output impedance will be 50 Ω – or if taken from one 150 Ω terminal and the C. T. terminal, the output impedance will be 37.5 Ω.
Connect the transformer input socket to the TF 1370A ATTEN output socket, by means of a coaxial lead fitted with BNC type plugs (e.g. , TM 4726/136), and connect the external load to the appropriate terminals on the transformer. Turn the ATTEN IMPEDANCE switch to 600 Ω, the OUTPUT VOLTS SELECTOR switch to SINE, 3 ATTEN, and adjust the oscillator and the output voltage as described in sections 2.5 and 2.6.
The centre tap of the secondary winding on the transformer may be connected to its earthed terminal to obtain an output that is balanced with respect to earth, or, if this connection is not made, an output may be obtained that is floating or at some d. c. potential with respect to earth; the maximum d. c. potential allowable between the primary and the secondary windings is 200 V.
The secondary source e.m.f. between the 600 Ω terminals is the same as the e.m.f. indicated by the TF 1370A. For other output impedances Table 2. 2 lists the multiplying factor necessary, due to the turns ratio of the transformer, that should he applied to the e.m.f. reading on the front panel meter to obtain the transformer secondary source e.m.f. When the transformer is loaded there is a small insertion loss; approximately 0.5 dB at 1 kc/s.
CAUTION
It is important that d. c. should not be allowed to flow in the windings of the transformer. 1 kc/s Band-Pass Filter Type TM 6222
The 1 kc/s Band-Pass Filter is for use with the TF 1370A to give very pure outputs of 1 kc/s sine wave signals at a source impedance of 600 Ω.
Connect the Band-Pass Filter input socket to the TF 1370A ATTEN output socket by means of a. coaxial lead fitted with BNC type plugs, and the two terminals on the Band-Pass Filter to the external load. Turn the ATTEN IMPEDANCE switch to 600 Ω, and the OUTPUT VOLTS SELECTOR switch to SINE, 3 ATTEN. Adjust the oscillator frequency to 1 kc/s and the output voltage to the required amplitude as described in sections 2, 5 and 2. 6 respectively. If a valve voltmeter is available, this should he connected across the load and the oscillator frequency adjusted for maximum valve voltmeter reading.
Assuming that the load is 600 Ω, a signal voltage measured across the load will be about 10% below half the e.m.f. indicated by the front panel meter. To ascertain the exact signal voltage across the load, proceed as follows:
(i) Turn the ATTENUATED OUTPUT switch to 3 V .
(ii) Adjust the SET OUTPUT control to give 3 V meter deflection.
(iii) Connect a valve voltmeter, set to read 1. 5 V, across the load and read the exact voltage.
(iv) The difference between the TF 1370A e.m.f. reading and the valve voltmeter reading, expressed as a ratio, may then be used to determine accurately the voltage across the same load at other, lower, levels.
The filter can be used with the ATTEN IMPEDANCE switch turned to 75 Ω, 100 Ω or 130 Ω, if some worsening of the second harmonic content and a larger insertion loss is acceptable.
Note: The filter should never be used without a terminating load.
×100 Attenuator Pad Type TM 6454
The ×100 Attenuator Pad matches the 75 Ω source impedance of the ATTEN output socket on the TF 1370A, and it is suitable for use with sine wave and square wave signals at all frequencies within the operating range of the instrument.
The Attenuator Pad has a BNC INPUT socket and two BNC OUTPUT sockets both giving 100 times e.m.f. attenuation. The input impedance is 75 Ω; the source impedance at one output socket is 75 Ω and at the other it is 5 Ω.
If, for any particular application, a 5 Ω source impedance is required with less attenuation, then the signal from the TF 1370A may be fed into the 75 Ω OUTPUT socket of the Attenuator Pad and the external load connected to the 5 Ω OUTPUT socket.
Under these circumstances the e.m.f. attenuation will be 30 times.
Note: The TF 1370A is not a fully screened signal generator and consequently errors in the signal level, due to
leakage, may occur at µV signal levels at the highest frequencies».
§§§
Il testo prosegue, come si legge all’inizio, nella scheda dedicata al Wide Range R-C Oscillator TF 1370°, Serial N° 54110/053. Marconi Instruments Ltd. England.
Abbiamo omesso il capitolo “Maintenance” del quale abbiamo scelto alcune figure.
Foto di Claudio Profumieri, elaborazioni e ricerche di Fabio Panfili. Testo a cura di Fabio Panfili.
Per ingrandire le immagini cliccare su di esse col tasto destro del mouse e scegliere tra le opzioni.

 

 

 

Precision Phase Meter Type 405L AD-YU Electronics Lab. Inc. Passaic. N. J. Seconda parte.
Nel cartellino verde visibile in diverse foto vi è la data “2/20/63” almeno così pare di leggere, cioè 20 febbraio  1963.
Nell’inventario D del 1956,  in data 28 maggio 1963, al n° 3284 si legge: “Ing. Mario Vianello – Milano. Misuratore di fase. Dest. Elettronica”.
Abbiamo così una conferma dell’anno di acquisto dello strumento.
Nel collaudo eseguito dalla ditta si legge la data: 28 novembre 1962.
Nella Sezione Elettronica sono conservati due manuali di istruzioni con un allegato dattiloscritto che riguardano questo strumento.
Riportiamo qui di seguito il testo dattiloscritto.

§§§
«Operating Instructions
For Type 405 Series Precision Phase Meter
COMPLETE CIRCUIT DIAGRAM:

Fig. 6 shows a complete circuit diagram of the instrument, Tubes T₁ to T₄ are connected as a four-stage cathode-coupled limiter for E₁ channel. Similarly, T₅ to T₈ are for E₂ channel. A gated beam tube, T₉, is used as a coincident slicer. The panel meter is activated by the plate current of T₉. When switch S₂ is on “TEST” position, the panel meter indicates the plate current of the output section of any limiter stage, T₁, T₂, T₃, T₅, T₆, or T₇, also T₄ and T₈ in 405H, depending on the position of S_4a. The bias voltage of any one of the eight limiter stages can be so adjusted as to maintain a constant plate current equal to the quiescent value, when the grid is excited by a symmetrical signal of which the amplitude varies from zero to the maximum permissible value. When any stage is so adjusted, its square wave output will be symmetrical provided that the amplitude of the input signal is never large enough to cause the tube to draw grid current.Fig. 7 shows a circuit diagram of the power supplies, which yield two
regulated B+ voltages and the heater voltages.
DESCRIPTION OF CONTROLS AT THE FRONT PANEL
1.“E₁ IN”, binding post – Provides a connection of the input signal to
E₁ channel.
2.“ADD – 0° – 180°”, 1-pole, 2-position switch (S₁ in Fig. 6). Add 180° to the meter reading at “180°” position, add nothing at “0°” position.
3.“DEFLECTION INC.”, potentiometer, 500-ohm (R₉ in Fig. 6), Used for adjusting the meter reading to 180° when both input channels are fed by an identical signal and “ADD” switch at “180°”.
4.“RANGE”, 2-pole, 5-position switch (S₂ in Fig. 6) .To select the sensitivity of the panel meter, 12°, 36°, 90°, or 180° full scale for 405 and 405L; 36°, 90°, 120° or 180° for 405H. In addition, it connects the meter to anyone of the output plate circuits of the cathode-coupled limiters at “TEST” position. This position is used for adjusting the bias voltage of the limiter in order to give a symmetrical output square wave.
5.“POWER ON”, a toggle switch – to turn on and off the line voltage.
6.“E₂ IN” – Provides connection of an input signal to E₂ channel.
7.“SENSE LP-HF”, 1-pole, 8-position switch (S₁₀ in Fig. 6) – Used to change the amount of phase lag at the plate of T₁ for SENSE identification, i.e. determining the relative lag or lead of E₁ with respect to E₂.
8.“READ”, a momentary push-on switch (S3 in Fig. 6) – For connection of a shunting capacitance at the plate of T₁ in order to introduce a lagging phase angle to the same channel for SENSE identification.
DESCRIPTION OF CONTROLS AT THE REAR OF CHASSIS:
1.“STAGE”, 3-pole, 8-position switch (S4 in Fig. 6), – For connecting the panel meter (when the “RANGE” switch is set at “TEST”) to the output plate circuit of one of the limiters, T₁ to T₃, T₅ to T₇, including T₄ and T₈ in 405H, and the input grid leak of the preceding limiter to push-button switch S₅.
2.“GR”, push-button switch (S₅ in Fig. 6) – For connecting the input grid leak of one of the limiters to ground in order to cut off the plate current and permit no signal feeding into the next stages
3.R₁₁ for calibration of the 180° range.
4.R₁₃ for calibration of the 90° range.
5.R₁₂ for calibration of the 360° range.
6.R₁₄ for calibration of the 12° (120° for 405H) range.
7.“OUT”, jack for connection to external recorder, quiescent potential at 300V ±10% for 405 and 405L, +280V for 405H.
8.“+300V”, jack at +300V ±10% B+ potential for 405 and 405L, +280V ±10% for 405H.OPERATING PROCEDURE:
1.Plug the line cord into 220 volts, 50/60 cycles, (220 volts available on request)
2.Apply a single signal to “E₁ IN” and “E₂ IN” simultaneously, (This signal should lie between 0.3 volt and 70 volts for models 405 and 405L, or 2 volts and 40 volts for model 405H)
3.Set “ADD” switch to 180° position, and adjust potentiometer for 180°
reading on panel meter. Now turn the “ADD” to 0° position and the instrument is ready for use.
4.Apply the two signals of which the phase difference is to be determined to “E₁ IN” and “E₂ IN” and read the phase difference on the panel meter.
5.To identify the “SENSE” of the meter reading, turn “SENSE LF-HF” control to “START” extreme clockwise position; push in the “READ” switch; then turn the “LF-HF” control slowly counterclockwise until the meter reading starts to change. If the reading starts to decrease, E₁ leads E₂; if the reading starts to increase, E₁ lags E₂.
6.There are two methods for use with an external recorder: (1) For d.c. coupling, connect the recorder (which must have both input leads isolated from ground) to the jack “OUT” at the rear of the chassis. The quiescent potential of this jack is +300 ±10% for 405 and 405L, +280 ±10% for 405H. An R-C integrating circuit with time constant of .005
second is installed internally at this jack. The output voltage referring to B+ is zero for 0°, increases linearly to -14 volts for 405 and 405L, -4 volts for 405H, as measured at the plate of 6BN6.
(2) If the signal frequency is above 60 cps, a capacitor can be used for coupling and for isolating the B+ potential, In this case, connect a capacitor, about 0.5 μf, to the lead for the negative terminal of the meter and disconnect the panel meter from the circuit, and set “RANGE” switch to “180°” position.
BIAS ADJUSTMENT:
Bias controls R₁ to R₈, on top of the chassis, should be adjusted if meter reading varies with change of signal amplitudes or is off zero when a single signal is applied to both inputs, or when tubes are changed in the limiter stages. The procedure for adjusting the bias control, R₁, for the limiter stage, T₁ is as follows:
1.Apply a single signal (about 200 cps, 10 volts or more, symmetrical with respect to the zero axis) to both “E₁ IN” and “E₂ IN”.
2.Set the “RANGE” switch to “TEST” and the “STAGE” switch at rear to T₁.
Take reading on meter.
3.Remove the input signal and short the input binding post to ground.
Take meter reading again.
4.Adjust R₁ until the meter reading of step 3 equals that of step 2. Repeat the above steps several times to insure that the output plate current of T₁ remains unchanged when the input signal varies from zero to over 10 volts.
The procedure for adjusting R₂ for the second limiter stage, T₂, is the same as described above, with the following exceptions: In step 2, set the “STAGE” switch to T₂; in step 3, push the “GR” switch and remove the input signal. Use a similar procedure to adjust R₃. The procedure for adjusting R₅ is similar to that of R₁. The procedure for adjusting R₆, R₇, is similar to that of R₂ and R₃. The order of adjustment must b from first to the second, to the third, to the fourth stage. This will insure that the input to the stage under adjustment (namely, the output of the previous stage) is a signal symmetrical with respect to the zero axis.
In 405H, the procedure for adjusting R₄ and R₈ is a similar to that of _R3.
In 405 and 405L, the procedure for adjusting R4 is as follows: (a) Connect an oscilloscope to the output plate of T₄, which can be reached without taking the cabinet off by pulling 6BN6, T₉, out from its socket, then insert a wire to pin #2 for adjusting R₄, pin #6 for adjusting R₈. (b) Apply a sine wave signal about 5 volts with frequency at 100 kc to 200 kc to E₁ IN binding post. (c) Adjust R4 until the output square wave at the plate of T₄ becomes symmetrical with input signal varying from 1 volt over 10 volts. Fig. 9 shows that the waveform is symmetrical when a₁ = a₂ and b₁ = b₂. The procedure for adjusting R₈ is the same as R₄.MAINTENANCE:
NOTE: When any one of the tubes, T₁ through T₈, is changed, the bias potentiometer of that tube must be adjusted according to the procedure, outlined in the previous section.
1.Defect – Meter reading changes with input signal amplitudes, and/or meter reading is not zero when a single signal is applied to both
“E₁ IN” and “E₂ IN”.
Cause – The bias voltages for one or more of the limiter stages has to be adjusted according to the described procedure. If the defect can not be eliminated after careful bias adjustment, it may be caused by one or more of the following causes: (a) Voltage across the grid leak, resistors (3 megaohms for 405 and 405H, 5.1 megaohms for 405L) is not zero: positive voltage due to leakage of coupling condenser or defective tube, negative voltage due to high output from previous stage or due to defective tubes of this stage or previous stage. (b) One or more of the limiter stages produces a round-top or round-bottom square wave due to defective tube (cut-off characteristics not identical between the two halves and also not sharp enough). This defect can be identified when the plate current indication on the panel meter varies with “RANGE” switch at “TEST” and input signal changes from a fraction of 1 volt to 20 or 30 volts. It also can be identified by using an oscilloscope to observe the output waveform with input signal just high enough to enable the starting of clipping. (c) Input signal is not symmetrical with respect to the zero axis. (d) A by-pass capacitor has excessive leakage in the first or second stage. This defect can be easily locate by using the following procedures:  (1) Use a jumper to short the plate of T₁ to the plate of T₅. If the meter indication becomes zero, the difficulty is in the stage of T₁ or T₅. If the meter indication is still not zero, move the jumper to short the plate of T₂ to the plate of T₆. If meter indication becomes zero, the difficulty is in the stage of T₂ or T₆. Otherwise, move the jumper to T₃ and T₇. By using this procedure, the cause for off-zero may be located.
2.Defect – Meter reading drifts or fluctuates during bias adjustment and for phase measurement.
Cause – (a) Poor regulation from the power supply, check OG3, 12AX7, or 6BL7, (b) Potential across grid leak resistor is not zero, see 1 (a). (c) Check all d.c. potentials. (d) A by-pass capacitor has excessive leakage.
3.Defect – Meter reading is not zero when a single signal with high (or low) amplitude is applied to both input, and/or phase readings differ when two input signals interchange.
Cause – The tubes in the first stages (or second stages) of both channels have very different characteristics. This may be proven by inter-changing the tubes in the first stage (or second stage) of both channels.
If off zero at high signal, T₅ is much weaker than T₁; if off zero at low signal, T₁ is much weaker than T₅.
4.Defect – Meter reads off-scale or insufficient. “DEFLECTION INC.” control cannot bring it within range.
Cause – Potentiometer R₁₁, located at the back of the chassis, has to be adjusted. This condition may also be due to a defective 6BN6 tube (T₉).
5.Defect – Phase reading in 12° (120° for 405H), 36°, or 90° range is incorrect.
Cause – The 90°, 36°, and 12° ranges must be calibrated by means of potentiometers R₁₃, R₁₂, and R₁₄, respectively. A circuit diagram for adjusting these potentiometers is given in Fig. 8. When frequency is 400 cps and C = 0.1 µf, the phase reading should be 10° for R = 702 ohms; 30° for R = 2.3 K; 70° for R = 10.93 K. The procedure is as follows;
(a) Hook up the circuit shown in Fig. 8. In this circuit, facility must be provided to vary either the resistor, R, or the oscillator frequency, F.
(b) With the “RANGE” switch at 180°, vary R or F until a phase shift of 70° is indicated on the panel meter.
(c) Using this setting of R and F, set “RANGE” switch at 90°, and adjust R₁₃ until a reading of 70° is indicated on the panel meter.
(d) Adjust R or F for reading of 30° on the 90° scale.
(e) Using this setting of R and F, set “RANGE” switch at 36°, and adjust R₁₂ until a reading of 30° is obtained on this scale.
(f) Adjust R or F for a reading of 10° on the 30° scale.
(g) Using this setting of R and F, set “RANGE” switch at 12°, and adjust R₁₄ until a reading of 10° is obtained on this scale. In case that the range of R14 is insufficient to obtain 10° reading, adjust “DEFLECTION INC.” control to a different position which makes 10° reading on the panel meter possible by adjusting R₁₄. Then set “RANGE” switch to 180° position, readjust R₁₁ for correct meter reading. Repeat procedures (f) and (g) for 90° and 36° ranges.
6.Defect – The sum of the phase readings at “0°” and “180°” positions of the “ADD” switch not equal to 360°.
Cause – At low frequencies, such as 200 cps, the bias voltage for one or more of the limiter stages has to be adjusted. At high frequencies, it is due to the values of R₁₆ and R₁₇ being in-correct. It may also be due to defective panel meter.
7.Defect – D.C. grid bias on all stages fluctuates.
Cause – (a) Defect of regulating power supplies. (b) defective tube, coupling condenser, or by-pass condenser in the limiter stages.
8.Defect – The gain of corresponding stages (e.g., T₁ to T₅, T₂ to T₆, etc.) in channels E₁ and E₂ is not equal.
Cause – This may be due to unequal cathode or plate resistors in the corresponding stages, or defective tube.
9.Defect- The B+ potentials of the power supply read too high.
Cause – Filaments on the 12AX7 of the power supply are open.
10.Defect – Ripple on sine wave, and signal is not steady (in any stage). Cause – This may be due to 60-cycle pickup from heater to grid, or
heater to cathode leakage. Replace the tube of the faulty stage.
11.Defect – Insufficient deflection on the sensitive scale (0-12° for 405, 405L; 0-36° for 405R), all other ranges are satisfactory.
Cause – 6BN6 has insufficient emission, or adjustment of potentiometer R₁₁ is incorrect, see Defect 5 (g).
12.Defect – Meter reading is not zero with a single input signal, phase reading stable by changing signal amplitudes and bias adjustment good.
Cause – Coupling capacitors, plate resistors, or cathode capacitors between two channels are not matched (should be matched within ±½% for all components used in the first and second stages). The method for locating the defect is given in 1 (e). If the reading is zero below 1 kc and not zero at higher frequencies, the location of various coupling capacitors should be adjusted.
13.Defect – Meter reading below zero with a single signal applied to both E₁ IN and E₂ IN.
Cause – Calibration potentiometer for the range in question has leakage to ground. Replace the potentiometer, or insulate the potentiometer from the chassis.
14.Defect Meter reading not equal for interchanging of input signals.
Cause – Signals have a large percentage of harmonics and noise, coupling resistors at input of 6BN6 are not correct, or incorrect bias Adjustment. It may also be due to too much stray capacitance to ground in one channel, add a trimmer in the other channel for balance.
CHECK ACCURACY OF PHASE READINGThe accuracy of the instrument can be checked by reversing the connections of the resistor-capacitor combination of Fig. 8. When the frequency is 400 cps and the capacitance is 0.1 µf, the reading is 10° for R = 702 ohms; after interchanging the resistor with the capacitor, see Fig. 8b, the reading should be 80°. Caution: The amplitude of both inputs should be above the minimum signal requirement of the instrument, 0.3 volt for 405 and 405L; 2 volts for 405H. Therefore, the oscillator output should be above E min./cos θ. For example, when C = 0.1 μf, R = 702 ohms, the minimum oscillator voltage should be 2.5 volts for the arrangement given in Fig. 8a for 405H; 11.5 volts when R is interchanged with C for 405H. See Fig. 8b for R = 2.3K, the meter reading is 30°; after reversing, the reading should be 60°. For R = 10.93K, the reading is 70°; after reversing, the reading should be 20°.
D.C. VOLTAGES AND RESISTANCES: All d.c. potentials listed in the tables given below were measured with a vacuum tube voltmeter having 11 megaohms input resistance. A voltmeter having a different input resistance may register a different voltage, especially the d.c. potentials on the grids. Furthermore, the values may differ from one set to the other by ±10% or slightly more. Measurement of d.c. voltages and resistances often locates the source of the defect.
USE OF EXTERNAL RECORDER WITH TYPE 405
An analog output is derived from the plate of the 6BN6 coincident slicer and is connected to the jack labeled “OUT” at the rear of the instrument. The output pulses are integrated via an R-C network which produces a time constant of 0.005 seconds and a D.C. source impedance of approximately 700k. The output scale factor is 77.7 millivolts per degree of phase reading on the Type 405 and Type 405L; 22.2 millivolts per degree on the Type 405H. These scale factors apply only for recorder input impedances which are considerably higher than the analog voltage source impedance. It should also be noted that the reference voltage for the analog output, available at the other rear jack is +300v  ±10% on the 405/405L and +280v ±10% on the 405H. This means that the recorder must be capable of off ground operation at the above stated voltages. The following sketch should further clarify the methods of driving extreme recorders. The choice of values of R and C depend on the signal frequency and the input impedance of the recorder. Higher value of R and C give better filtering but more attenuation of the signal applied to the recorder. In general R = 500k to 1 meg and C = 0.1 μfd to 0.5 μfd are sufficient for most applications except in cases where the signal frequency is below 60 cps. Here it is recommended that the value of C be increased to 1 or 2 μfd in order to achieve better filtering of ripple». §§§
Per consultare la prima parte scrivere “405L” su Cerca.
Foto di Claudio Profumieri, elaborazioni e ricerche di Fabio Panfili. Testo a cura di Fabio Panfili.
Per ingrandire le immagini cliccare su di esse col tasto destro del mouse e scegliere tra le opzioni.

Precision Phase Meter Type 405L AD-YU Electronics Lab. Inc. Passaic. N. J. Prima parte.
Nel cartellino verde visibile in diverse foto vi è la data “2/20/63” almeno così pare di leggere, cioè 20 febbraio  1963.
Nell’inventario D del 1956,  in data 28 maggio 1963, al n° 3284 si legge: “Ing. Mario Vianello – Milano. Misuratore di fase. Dest. Elettronica”.
Abbiamo così un indizio sia  dell’anno di acquisto dello strumento sia che si tratti di questo strumento.
Nel collaudo eseguito dalla ditta si legge la data: 28 novembre 1962.
E in uno dei due manuali di istruzioni si legge: “Manufactured in USA June 1962”.
Nella Sezione Elettronica sono conservati due manuali di istruzioni con un allegato dattiloscritto che riguardano questo strumento. Ne riportiamo alcune parti.

§§§
A NOVEL METHOD FOR ADJUSTMENT OF SYMMETRICAL SQUARE WAVES:
A simple method for adjusting the bias voltages based on the principle of zero average current for a perfectly symmetrical sine wave or square wave, which has better accuracy than the use of an oscilloscope, has been discovered and is employed in our Type 405 Series. The adjustment is made by using the d-c microammeter of the instrument (properly shunted and connected in series with R_b)- A symmetrical sine wave applied to the input terminal results in a meter reading of I₁. With the input signal removed, bias voltage E_c1 is adjusted until the meter, which is now measuring the quiescent plate current of V₂, is again reading I₁. These steps are repeated until meter reading remains unchanged for variations in input signal amplitude from zero to maximum. Panel switches are installed in the instrument for the convenience of the operator to adjust the bias voltage of any one of the eight limiter stages by using the panel meter as indicator for symmetry. This arrangement provides a simple and convenient method to insure proper operation of the limiter stages, and increases the accuracy of the instrument.
COINCIDENT SLICER:

FIG. 4 shows a circuit diagram of a coincident slicer where a gated beam tube with two control grids, G₁ and G₃ is employed. Both G₁ and G₃ are biased positively with respect to their cathode and both applied signals are negative. The plate current of the gated-beam tube cannot flow unless G₁ and G₃ are above their cutoff value simultaneously. When either or both input signals are at their cutoff values, plate current cannot flow. In FIG. 4, E₁ and E₂ represent the output signals from the two last stages of the cathode-coupled limiters, CL₁₄ and CL₂₄. In order to have better accuracy for measuring small phase angles, the rise time of the output square waves can be made very short by introducing positive feedback to these stages. Dotted line #1 and dotted line #2 represent the cutoff and saturation levels, respectively, of the gated-beam tube used in the coincident slicer. Let l_b represent the wave-form of the plate current of the coincident slicer. Since the irregularities of both input signals, such as rounded corners and overshoots, are outside the region of dotted lines #1 and #2, the plate current will not be affected by such irregularities. Another advantage of using a coincident slicer is that the output meter reading can be made virtually independent of the variations in output amplitudes of the cathode-coupled limiters, or supply voltages of the tubes.
GENERAL INTRODUCTION:

FIG. 1 shows a block diagram of Type 405 Precision Phase Meter. Input signal E₁ is applied to the four-stage cathode-coupled limiter, CL₁₁ to CL₁₄. The function of a cathode-coupled limiter is to produce a square wave with its zero-axis intersecting points remaining identical to those of the input signal. Both input signals are first transferred into the square wave by means of two separate four-stage cathode-coupled limiters, positive feedback is provided in CL₁₄ and CL₂₄. for decreasing the rise time of the output square wave, and then fed into a coincident slicer circuit, which is used to activate the panel meter.
FIG. 2 shows the waveforms at various points of the instrument. E₁ and E₂ are input signals. E₁’ and E₂’ are output signals of the two cathode-coupled limiters, CL₁₄ and CL_24.  I_ba can be expressed as follows:
I_ba =  I_bp  t₁/T = k180° — kθ
where I_bp is the peak value of the plate current of the coincident slicer and k is a constant. It is seen, therefore, that the output meter can be calibrated to read the phase angle between E, and E: directly in degrees when either E, or E2 is shifted 180°.
CATHODE COUPLED LIMITER:
A cathode-coupled limiter is shown in Fig. 3. The grids of V₁ and V₂ are biased with positive potentials E_c1 and E_c2. When the input signal increases above zero, plate current of V₁ increases, raising the cathode potential of both V₁ and V₂. Since the bias voltage of E_c2 of V₂ is held constant, the grid-to-cathode potential decreases, reducing the plate current of V₂ and raising its plate potential, or output. This action continues until V₂ is driven to cutoff and the output can no longer follow the input but remains at the plate-supply voltage level. The output remains constant until the input to V₁ reduces to a level which will permit plate current to flow again in V₂. Since the grid of V₂ is held constant with E_c2, tube V₁ will cutoff when the input signal reduces to a certain level. At this level, the plate potential of V₂ will be constant again. Before limiting action occurs, the gain of a cathode-coupled limiter is approximately equal to
 μR_b/2(R_b + R_P),
where R_b, is the load resistance at the plate of V₂, R_p is plate resistance of the tube, and μ, is the amplification factor of the tube. Using conventional duotriodes, an overall gain of 10,000 is obtained with four stages of cathode-coupled limiters. This high amplification, combined with limiting action, removes more and more of the curved portion of the input waveform until the resultant waveform at the output of the last stage is a square wave with practically vertical sides.
FEATURES
1.Meter reading independent of the ratio of input signal amplitudes.
2.Equal accuracy for symmetrical waveforms of any shape.
3.Direct indication of phase angle in degrees from 500 kc down to 1 cps.
4.No amplitude adjustment of either signal voltage.
5.No ambiguity at zero reading.
6.Provision for identification of “LEAD” and “LAG.”
7.Provision for self-calibration and self-adjustment.
DESCRIPTION-Type 405 Series is the most stable and convenient instrument available for measuring a phase angle between two alternating voltages, without either amplitude  or frequency adjustment. In addition to its capability of presenting the phase angle directly in degrees on an 8″ rectangular panel meter with mirror scale is also capable of plotting phase-frequency curves on a recorder or oscilloscope. Furthermore, this instrument presents no ambiguity at zero reading, and is perfectly stable for measuring a small fraction of one degree on all ranges including the 0-12° range; whereas other commercially available phase meters always fluctuate when the phase angle to be measured is below 3 or 4 degrees. Type 405 Series is particularly suitable for production work, because it is very simple to operate — no amplitude adjustment, no zero adjustment, no frequency adjustment, and direct reading in degrees on a large panel meter with a 6.5″ mirror scale. In addition,  high sensitivity, good accuracy, self-checking and extreme bandwidth are features which make it a uniquely valuable phase instrument for development and research laboratories.
APPLICATIONS
Besides the applications given in Fig. 5 to 9, there are  a number of other applications, which include:
(a) Direct indication of phase characteristics with respect to  frequency and/or amplitude of servo systems, process control equipment, transducers, simulators, aircraft control systems; etc. (b) Correlation  between two signals  can be measured with Type 405H Phase Meter and a unit of Ad-YU Type 802 or Ad-YU Type 606 Variable Delay Line. Type 802 has total delay up to 200 milliseconds, with resolution one part  per, 10,000.  Type 606 has 120 positions and may be driven by motor. (c) In conjunction with Ad-Yu. Type 305 Frequency Converter; Type 405 or 405H can be used to plot phase angles up to 100 mc.Fig. 5—Automatic plotting of phase response curve with respect to change of frequency and/or amplitude of electrical networks, can be achieved by applying the output to a recorder with both signal terminals above ground potential. A capacitor (approximately 2 μf) should be connected from the chassis of Type 405 to the ground of the recorder for filtering out hum pickup. Fig. 6 – Precision phase measurement with 0.25° accuracy can be achieved in production lines by comparing a known phase shifter with the unknown network under test on the 0-12° (or 0-36°) range. The known phase shifter may be a series RC with tan θ   ≃ RWC if θ is less than 90°, close coupled transformer if θ = 180°, or Ad-Yu Type 208A Precision Phase Shifter Generator.

Fig. 7 – Phase measurement with error less than 0.25° in the vicinity of +90° can be accomplished by arranging R₁ = R₂, C₁ = C₂ and using the 0-12° range. For measurement in the vicinity of – 90°, interchange the positions of E₁ and E₂ signal sources. At 0-180° range, the meter will indicate 0° at center  +90° at right -90° at left.
R₁ = R₂ ≃ 1/WC₁, or 3/ WC₁ > R₁  > 1/ 3WCFig. 8- Combination of Type 405L and a matched pair of A103 Band-pass Filters enables accurate phase measurement with excessively distorted signals from strain gauge, pressure pickup, transducer, vibration pickup, force transducer, etc.
Fig. 9- A voltage divider may be used to equalize the amplitudes of two input signals for 405 series, see Fig. 9a for amplifiers, step-up transformers, etc., Fig. 9b for potentiometers, step-down transformers, etc. To minimize phase error due to stray capacitance, at least one element of the divider should be made less than 100 ohms.ACCESSORIES
SPECIFICATIONS

RESPONSE:
TYPE 405 — 8 cps to 40 kc; the upper limit can be extended to 100 kc with increasing signal amplitudes and decreasing accuracy.
TYPE 405H — 8 cps to 300 kc; the upper limit can be increased to 500 kc with increasing signal amplitudes and decreasing accuracy.
TYPE 405L — 1 cps to 40 kc; the lower limit can be extended to less than 1 cps with increasing signal amplitudes. The upper limit can be extended to 100 kc with increasing amplitude and decreasing
accuracy.
PHASE RANGE:
There are four ranges — 0-12, 0-36, 0-90, and 0-180 degrees full scale. A panel switch is provided for inserting 180 degrees phase shift in order that the above four ranges may be converted to four additional ranges; 180-192, 180-216, 180-270, 180-360. The 12° range is converted to 120° in TYPE 405H.
ACCURACY:
The term relative accuracy means the accuracy of difference in phase reading from one condition to another. For example, it may be interpreted as accuracy of (1) repeatability, (2) comparison of readings among unknown signals with respect to a given signal, (3) relative phase angle due to variation of signal characteristics, such as change of frequency, amplitude, or the characteristic of the network through which one (or both) input signal flows. The term absolute accuracy means the accuracy of the phase reading in comparison with a phase standard. All the figures quoted below for accuracy are the maximum values of errors which have been found so far for a number of instruments of this series. However, experience has shown that errors are actually much less than the figures given below for many instruments.
TYPE 405 – The relative accuracy is ±0.25°, and the absolute accuracy is ±1° or 2% at any range up to 40 kc; the error increases slowly up to ±3% at 100 kc.
TYPE 405H – The relative accuracy is ±0.25°, and the absolute accuracy ±1° or 2% at any range up to 300 kc; the error increases slowly up to ±3% at 500 kc.
TYPE 405L – The relative accuracy is ±0.25° and the absolute accuracy is ±1° or 2% at any range from 1 cps up to 40 kc; the error increases slowly above 40 kc to 3% at 100 kc; below 1 cps, the error is due to slow movement of the meter pointer at signal frequency. For all three types the absolute accuracy is much less than 1° when measuring small phase angles.
INPUT VOLTAGE:
The phase reading on the panel meter is not affected by the fluctuation of signal amplitudes in either one or both input channels within the ranges listed below.
“Manufactured in USA June 1962”.
TYPE 405 — The signal voltage can be varied from 0.3 volt to 70 volts rms from 8 cps to 40 kc (0.1 volt possible with relaxed accuracy); the lower limit increases slowly to 0.5 volt at 100 kc. The d.c. component should not be more than 400 volts. TYPE 405H — The signal voltage can be varied from 2 volts to 40 volts rms from 8 cps to 250 kc (with relaxed accuracy, 0.3 volt possible below 100 kc, 1 volt possible below 300 kc). The d.c. component should not be more than 400 volts.
TYPE 405L — The signal voltage can be varied from 0.3 volt to 70 volts from 1 cps to 40 kc (0.1 volt possible with relaxed accuracy); the lower limit increases for frequencies below 1 cps and above 40 kc. The d.c. component should not be more than 200 volts.
INPUT SIGNAL RATIO:
Meter reading is completely independent of the ratio of signal amplitudes, ranging from ratios of 1 to 100 for TYPE 405 and 405L, and 1 to 20 for TYPE 405H.
INPUT IMPEDANCE:
TYPE 405 and 405H – 3 megohms shunted by 20 μμf on both input channels.
TYPE 405L — 6.8 megohms shunted by 20 μμf.
INPUT POWER:
60 watts, 50/60 cycles at 110 volts ±10% (220 volts ±10% available on request at no additional charge).
STABILITY FOR MEASURING SMALL PHASE ANGLES:
Drift is less than 0.01° for 10 hours of continuous operation at the vicinity of zero degree.
CHARACTERISTIC OF OUTPUT SIGNALS:
The output signal for external recorder taken at the meter terminal is a pulse of constant amplitude with repetition rate equal to the input signal frequency and duty cycle proportional to the phase angle between two input signals. Both the repetition rate and duty cycle follow instantly any change of input signal frequency and phase angle. An integrating circuit with time constant of 0.1 second is connected in series between the meter terminal and the “OUT” jack at the rear of the chassis. The output impedances are 3.6 k and 360 k respectively before the integrating circuit and after. Output voltage referring to B+ is zero for 0° increases linearly to -14 volts for 180° in 405 and 405L to  -4 volts for 405H, decreases again to zero from 180 to 360°.
WAVEFORM DISTORTION:
Reading is not affected by harmonics which are 0° and 180° with the fundamental components. Harmonics, which result in difference of time duration between the positive and negative portion of the waveform, will produce error.
This error can be minimized by using a matched pair of AD-YU Type A103 filters.
PHYSICAL SIZE AND PRICE:
Panel— 19″ × 10%”, rack mount. Chassis—17″ × 8%” × 2¼”. Cabinet—12″ × 10″ × 20%”, light gray wrinkle finish. Type 405—$668, Type 405H—$725, Type 405L—$735.

OPERATING PROCEDURE
1.Plug line cord into 110 volts (220 volts available on request). 50/60 cycles. Set “RANGE” switch to 180° and “ADD” switch to 180°.
2.Apply to both “E₁ IN” and “E₂ IN” a signal greater than 0.3 and smaller than 70 volts for 405 and 405L. 2 to 40 volts for 405H.
3.Adjust “DEFLECTlON INC.” potentiometer for 180° reading on the meter. Now turn “SHIFT” switch to 0° and the instrument is ready for use.
4.Apply two signals separately to “E₁ IN” and “E₂ IN” and take readings.
5.To identify the SENSE of the meter reading, turn SENSE E₁ SHIFT control to the extreme right, push “READ” switch, then turn E₁SHlFT control slowly to left until the meter reading starts to increase if E₁ lags E₂, or starts to decrease if E₁ leads E₂. lf meter reading does not change, or changes illogically, it is probably due to the amplitude of E₁ being too high.
CAUTION:
Set “RANGE” to “TEST” to prevent damage of meter pointer by changing leads.
BIAS ADJUSTMENT:Bias controls R₁ to R₈ on top of chassis should be adjusted if meter reading varies with change of signal is applied to both inputs, or replacement of tubes in the limiter stages.
1.Apply a single signal about 400 cps, 5 volts or more, symmetrical with respect to the zero axis to both “E₁ IN” and “E₂ IN”.
2.Set “RANGE” switch to “TEST”.
3.Set “STAGE” switch at rear to “T₁” .
4.Take meter rading.
5.Reduce input signal to zero. This may done by grounding “IN” binding post for T₁ and T₅ stages, or pressing “GR” push button switch at rear and removing in put signal for other stages.
6.Adjust “R₁” until meter reading equals that of Step No. 4.
7.Repeat above steps several times to insure that the output plate current of T₁  remains unchanged when signal varies from zero to over 10 volts. Then turn “STAGE” switch to “T₂” and adjust bias pot constant. Use similar procedure for R₃. Order of adjustment must be made from first, second, third, then the output stage, such as R₁ to R₃ and R₅ to R₇, because the input signal of the stage being adjusted must be symmetrical with respect to the zero axis. Adjustment of R₄ and R₈ are normally un necessary. If adjustment are needed, the procedure for 405H is identical to that of R₂.  The procedure for 405 and 405L is as follows: Connect an oscilloscope to the plate of T₄ and adjust R₄ until the output square wave at the plate of T₄ becomes symmetrical with input signal above 5 volts and above 100 kc at “E₁ IN”. The procedure for adjusting R₈ is similar to R₄.»
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Per consultare la seconda parte scrivere “405L” su Cerca.
Foto di Claudio Profumieri, elaborazioni e ricerche di Fabio Panfili. Testo a cura di Fabio Panfili.
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Wide Range Oscillator Hewlett Packard, mod. 200CD, serial numberG 730-03469,W.-Germany.
Dono della Fondazione Carlo e Giuseppe Piaggio – Genova.
Nell’estratto di inventario della Sezione Elettronica, in data febbraio 1968 al n° 198 si legge: “N° D 42324-35. Oscillatore 230 V  ( HP 200CD)”. Mentre scriviamo questa scheda purtroppo non disponiamo dell’inventario generale D dell’epoca per ulteriori dettagli, ma sappiamo che gli esemplari acquistati erano due.
In internet si trova molta documentazione che riguarda lo strumento; per consultare il manuale di istruzioni si può andare all’indirizzo:
http://www.hparchive.com/Manuals/HP-200CD-Manual-SNP_605.PDF

 Il testo che segue con le relative figure  è tratto dal manuale di istruzioni conservato presso la Sezione Elettronica.
§§§
SECTION I
GENERAL INFORMATION
1-1. DESCRIPTION.
1-2. The Model 200CD Wide Range Oscillator generates frequencies of excellent waveform in the subsonic, audio, and ultrasonic ranges (5 cycles to 600 kc, in five overlapping decade bands). The Mode1200CD includes new design features which result in still finer performance than previous Hewlett-Packard instruments. Special circuitry ensures an output voltage of low distortion and high stability with any output load impedance from zero ohms to open circuit. Usefulness of the oscillator has been extended by designing the 200CD output circuit so that the instrument may be operated balanced as well as unbalanced and by providing a 600-ohm impedance match.
1-3. The Model 200CD is easy to operate: frequency and amplitude of the output voltage are set merely by operating dials on the control panel. The easily- read, 6-inch diameter frequency dial is calibrated over 300° of arc, and has an effective scale length of approximately 80 inches.
1-4. The Model 200CD furnishes up to 10 volts into a 600-ohm load (20 volts open circuit) at any frequency from 5 cps to 600 kc. A bridged tee variable attenuator in the output circuit controls the output power.
1- 5. The Model 200CD provides an ideal signal source for testing servo and vibrating systems, medical and geophysical equipment, audio amplifier circuits and transducers, sonar and supersonic apparatus , carrier telephone systems, video frequency circuits, and low radio-frequency equipment.
1-6. DIFFERENCES BETWEEN INSTRUMENTS.
1-7. Hewlett-Packard uses a two-section eight-digit serial number (000-00000). If the first three digits of the serial number on your instrument do not agree with those on the title page of this manual, change sheets supplied with the manual will define differences between your instrument and the Model 200CD described in this manual.
1-8. BACKDATING SHEET.
1-9. A backdating sheet that makes this manual applicable for instruments with serial prefixes to 103,  is provided in The Appendix of this manual.
SECTION II
PREPARATION OF USE
[Omissis…]
2-6. POWER REQUIREMENTS.
2-7, The Model 200CD requires a power source of 115/230 volts +10%, 50/1000 cps, 75 watts.
[Omissis…]
2-11. 230-VOLT OPERATION.
2-12. The Model 200CD is normally wired for operation from a nominal 115-volt supply. Operation from a 230-volt source is easily accomplished by reconnecting the dual 115-volt primary windings of the power transformer from a parallel configuration to a series configuration. (See figure 5-9). At the time of the change, replace the 1. 25 amp, slow-blow line fuse with a 0.6 amp, slow-blow line fuse.
SECTION III
OPERATING INSTRUCTIONS
3-1 . INTRODUCTION.
3-2. This section contains operating instructions for the Model 200CD Wide Range Oscillator. Figure 3- 1 gives basic operating instructions. The remainder of this section supplements these instructions.
3-3. OPERATION.
3-4. ON. The oscillator is ready for use as received from the factory and will give specified performance after a short warmup period. Turn oscillator on and allow approximately five minutes to warm up. Where maximum accuracy is desired, this warm-up period should be extended to at least thirty minutes.
3-5. RANGE. The RANGE is selected with the five position RANGE switch_ The position of this switch indicates the multiplying factor for the frequency dial calibration.
3-6. FREQUENCY dial. The frequency dial varies the frequency between the RANGE switch steps. The dial is calibrated from 5 to 60 and its indication multiplied by the factor indicated by the RANGE switch will give the actual output frequency of the oscillator. The small knob below the frequency dial is a vernier control for the dial.
3-7. OUTPUT CIRCUIT OPTIONS. The output circuit of the Model 200CD may be arranged for balanced or unbalanced operation. Typical connections for each are indicated in figure 3-2.
a. Unbalanced Operation. To operate with sidegrounded, a strap is placed between the G terminal,as indicated in figure 3-2A,
b. Balanced Operation. Connections for balanced operation are indicated in figure 3-2B. (The broken line from the ground terminal indicates the output circuit is balanced to ground, within the tolerances given below.
3-8. The AMPLITUDE control in the output circuit is a bridged-T attenuator and at any setting except minimum attenuation unbalances the circuit. Therefore, for balanced operation the AMPLITUDE control must be set for maximum output (full clockwise). Output balance also is a function of frequency because of capacitive feed-through at higher frequencies. Up to 10 kc, however, unbalance is less than 0.1%, and at B00 kc is approximately 1%. If small outputs are desired, or if balance at higher frequencies is critical, turn the AMPLITUDE control maximum clockwise, and connect an external attenuator, designed for the frequencies involved, between the Model 200CD and the load.
3-9. A balanced output may also be obtained over the full range of the AMPLITUDE control by using an hp AC-60A/B Line Matching Transformer at the output terminals of the oscillator.
3-10. The following chart indicates the area where within 1% of balance may be obtained. This chart indicates balance obtainable at various settings of the AMPLITUDE control when operating into a 600-ohm load. Where other values of load are used, the chart does not apply directly but does apply for settings of the AMPLITUDE control that would produce the indicated voltage across at 600-ohm load. SECTION IV
THEORY OF OPERATION
4-1 . GENERAL.
4-2. The Model 200CD Wide Range Oscillator uses a balanced (push-pull) oscillator circuit from which the output is taken directly, avoiding the complication and possible distortion of an isolating amplifier. Reaction of the load on the oscillator is avoided by the use of a zero source impedance output stage. This arrangement results in a simple, trouble-free circuit having low distortion and high stability over the entire frequency range.
4-3. Functionally, the circuits of the Model 200CD include a frequency-controlling bridge and balanced push—pull amplifier which constitute the oscillator circuit, an output circuit which may be arranged either for balanced or unbalanced operation, and a power-supply circuit. These are shown in block diagram form in figure 4-1 and in detail in the schematic diagram.
4-4. FREQUENCY-CONTROLLING BRIDGE.
4-5. The frequency-controlling circuit is arranged as a floating bridge, symmetrical with respect to ground. With no connection to ground on any terminal of the bridge, stability of calibration is assured since any stray capacity or leakage to ground present at the bridge output terminals does not shunt either the frequency-controlling or amplitude-stabilizing arms of the bridge. The frequency- controlling components (RC networks which are varied by operation of the RANGE switch and frequency dial) comprise two arms of the bridge, while the amplitude-stabilizing components (a voltage divider which includes a thermally- sensitive resistance) comprise the other two arms. The amplitude is stabilized at such a level that the amplifier tubes are operated in the substantially linear portion of their characteristics, which, together with the large negative feedback at harmonic frequencies, results in a very pure sine wave oscillation.
4-6. The bridge is fed by the balanced voltage developed at the cathodes of V2 and V4 in the output of the balanced amplifier. The output of the frequency-controlling branch of the bridge is applied to the grid of V3 and the output of the amplitude-stabilizing branch is applied to the grid of V1. The manner in which the voltage-versus-frequency and phase-versus-frequency characteristics of an RC network can be utilized with an amplifier of proper design to achieve an oscillator which delivers a voltage of excellent stability and wave-form is well covered in texts such as Terman & Pettit’s Electronic Measurements.
4-7. Variable resistor R11 is provided for adjustment of the amplitude-stabilizing branch of the bridge should it be found alter replacement of lamp RT1 or RT2 that less or more than rated voltage is being delivered to the output terminals.
4-8. Variable capacitors C3, C6, andC7 are adjusted at the factory for optimum calibration and amplitude constancy with frequency. They should not require adjustment unless the RANGE switch is replaced.
4-9. AMPLIFIER.
4-10, The oscillator amplifier is a balanced push-pull circuit including a voltage -amplifier stage (V1, V3) and a special cathode-follower stage (V2, V4). Criss-cross positive feedback is used in the cathode-follower stage to provide an essentially zero output impedance as seen by the cathode-to-cathode load. The feedback paths are from the plate of V2 to the control grid and screen of V4, and from the plate of V4 to the control grid and screen of V2. The degree of the positive feedback is a function of the load and increases as the load impedance decreases, thus tending to maintain the output constant regardless of load. Self-oscillation in the amplifier circuit is prevented by proper choice of resistance in the feedback circuits and by controlling plate and cathode impedances over the entire frequency range of the oscillator. The output stage is protected against a cathode-to-cathode short circuit by the resistors in series with the transformer secondaries. These resistors also make the oscillator present a 600-ohm impedance to the attenuator.
4-11. OUTPUT CIRCUIT.
4-12. Transformer coupling provides isolation between the oscillator circuit and the output circuit, and allows the output to be obtained either balanced or unbalanced. Since a single transformer will operate suitably over only a part of the frequency range covered 200CD, two transformers are provided. Connections between cathode-followers V2 and V4 and the proper transformer for the band in use are set up by the RANGE switch. The Secondary windings of the coupling transformers supply a conventional bridged tee attenuator, the setting of which is adjusted by operation of the AMPLITUDE control on the front panel. As the control is turned counterclockwise, the loss inserted by the attenuator is increased. The source impedance at the output terminals is 600 ohms.
4-13. With attenuator set for minimum loss, the output circuit is arranged for balanced operation, and is so designed that for frequencies up to 10 kc, stray capacity and leakage resistance will cause less than 0.1% unbalance. Unbalance at 600 kc is approximately 1%.
4-14. When it is desired to operate unbalanced, ground should be connected to the center output terminal, the termination for the connection brought out from terminal 6 of output transformers T1 and T2. Proper operation cannot be obtained if the ground is connected to the Bide of the circuit which includes the attenuator».
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La sezione Maintenance è stata omessa insieme ad altre parti. Di queste abbiamo riportato alcune figure che riteniamo interessanti.
Per consultare la versione in italiano scrivere “200CD” su Cerca.
Foto di Claudio Profumieri, elaborazioni e ricerche di Fabio Panfili.
Per ingrandire le immagini cliccare su di esse col tasto destro del mouse e scegliere tra le opzioni.