The thermistor is situated inside the screening box, just below the range switch. In the event of this being damaged, a tested thermistor should be obtained from this company.
Due to the high resistances used on the low frequency range, the instrument is sensitive to humidity. This is evidenced by weakness or cessation of oscillation on Range C, together with a drift of frequency. If this occurs, then the instrument should be left running, when after 15-30 minutes the moisture will be dissipated by the internally generated heat, and normal operation will return.
In all cases of difficulty the instrument should be returned to the factory for repair or adjustment
Page Eight
ADVANCE AUDIO FREQUENCY
SIGNAL GENERATOR
TYPE H.I.
INTRODUCTION
This Generator is intended primarily for fidelity and distortion checks on radio and television receivers, and high quality audio frequency amplifiers and record players. For these purposes, the wide frequency coverage of 15 - 50,000 c/s at constant voltage, and the low distortion of less than 1%, will be found ideal.
An optional square wave output is provided, which gives a good waveform approximately 50 : 50 ratio up to about 25 kc/s. This is useful for checking transient responses of video and other wide band amplifiers.
INSTRUCTIONS
POWER SUPPLY
The instrument is normally despatched with mains transformer set to operate from 210 - 250 volts supplies. For 105 - 125 volts it is necessary to change the tapping. To do this Remove the disc on the underside of the case, exposing the mains transformer. For 210 - 250 volts input tag 2 is connected to tag 3. For 105 - 125 volts remove the connection between tag 2 and tag 3. Connect tag 1 to tag 2 and tag 3 to tag 4. Replace the cover disc.
The instrument is suitable for A.C. supplies ONLY at frequencies between 40 c/s and 100 c/s.
The model H.l., N.A., is supplied with the transformer permanently set to operate on 115 - 120 volts supplies, at 25 - 60 c/s only.
Page One
VALVES AND ACCESSORIES
2 Valves type 6SN7GT Brimar.
I Valve type 6X5GT Brimar.
1 Thermistor type 1522/100 S.T.C.
I Pilot lamp type MES 11 mm. 6.5 volts.
A low capacity audio frequency lead, type PL 26, complete with plug and crocodile clips, is supplied with the instrument.
FREQUENCY RANGE
A sinusoidal signal of any frequency between 15 c/s and 50 kc/s is obtainable with an accuracy of ½ 1 % t 1 c/s by means of a directly calibrated dial and a three range selector switch. The bands are
A - 4,000 - 50,000 c/s
B - 300 - 4,000 c/s
C - 15 - 300 c/s
The total scale length is approximately 18 inches.
SINE WAVE OUTPUT
By means of the step and variable attenuators, a sinusoidal output at any level between 200,£V. and 20 V. is available from the output socket at any frequency on the dial.
The voltage into the attenuator is maintained constant within # 1 db. of the nominal value by means of the internal circuits of the generator,- and a further variation of ½ 1 db. may be found on the attenuated output, due to the use of 5% resistors in the attenuator.
The distortion of the output voltage is extremely small, as each generator has a measured total distortion factor of less than 1% at 1,000 c/s when checked at the factory. Normally the distortion is less than 1% between the limits of 100 c/s and 10 kc/s. The distortion consists of harmonics of the signal frequency, and hum at power supply frequency, in approximately equal amounts. It is measured on a normal type distortion meter, on which the percentage distortion is given as follows
Page Two
CIRCUIT CODE
R 1 13 MΩ ± 1% 2W R19 5kΩ ± 5 RMA 9
R 2 1 MΩ “ ½ W R21 220kΩ ± 10% RMA9
R 3 70 kΩ “ ½ W R22 25 kΩ ±10% linear wound pot
R 4 13 MΩ “ 2W R23 22kΩ ± 10% RMA 8
R 6 70 kΩ “ ½ W R24 500Ω “ RMA 9
R 8 250 kΩ ± 5% RMA 9 R25 2.2kΩ “ RMA 8
R 9 22 kΩ ± 10% RMA 8 R26 50kΩ linear wire-wound pot.
R 10 500 Ω “ RMA 9 R27 68kΩ ± 5% RMA 8
R 11 5 kΩ ± 20% carbon pot. R28 6.8kΩ “ RMA 9
R 12 220 kΩ ± 10% RMA 9 R29 680 “ RMA 9
R 13 22 kΩ “ RMA 8 R30 68Ω “ RMA 9
R 14 1kΩ “ RMA 9 R31 15Ω “ RMA 9
R 15 5.1 kΩ “ RHA 8 R32 12Ω “ RMA 9
R 17 220 kΩ “ RMA 9 R33 22Ω ± 10% RMA 8
R 18 22 kΩ “ RHA 8 R34 22Ω “ RMA 8
R35 2.7kΩ “
Page Seven
Cl 3 - 50 pF Air trimmer, Philips.
C2 13-532 pF ) 2 gang variable condenser.
C3 13-532 pF )
C5 .1 µF 350 V DCW ± 10% oil filled tubular.
C6 .1 µF “ “ “
C7 8 µF 500V 6CW elect. (part of block).
C8 .1 µF 350V DCW ± 20% paper tubular.
C9 .1 µF “ “
C 10 .1 µF “ ...
ciasteczkowypotwornie