Calibration
Equipment Required
Oscilloscope
Distortion Meter
4·5 digit Multimeter
Reciprocal counting Frequency Meter
Only the case lower need be removed to gain access to all adjustments. Allow 1 hour warm-up
(with the case lower in place) before commencing. For best results, use the following procedure.
1. Power Supply
+15V ± −20mV - VR23 −15V ± 20mV - VR24
+12V ± 0·5V
−12V ± −0·5V
+5V ± 0·25V
−5V ± −0·3V
+5VA ± 20mV - VR38 +6V ± 0·5V
2. Offset Nulling
Select: 5k range, frequency vernier to 3·0, sweep OFF.
IC TP Adjust DVM Reading
4 2 VR6 <40µV
22 3 VR7 <40µV
16 6 VR13 <40µV
3. Nulling of the triangle amplifier is achieved by shorting its input (TP5) and adjusting VR14
to give <2mV on TP4.
4. Preamplifier and Output Amplifier DC Offsets
Ensure that the DC offset control is at its centre detent. Release all three function buttons.
Amplitude control to minimum, adjust VR16 for <5mV at the main output.
Amplitude control to maximum, adjust VR15 for <5mV at the main output.
5. Waveform Symmetry
5k range, vernier at approximately 4, squarewave, adjust VR8 for equal mark:space ratio
using the oscilloscope x10 X-multiplier to increase resolution and the trigger slope switch.
5M range, vernier to approximately ·005 to give 5kHz to 6kHz, adjust VR5 for equal
mark:space ratio.
6. Frequency Calibration
Connect the Frequency Counter to AUX output.
Select external count and apply a frequency standard to AM/COUNT IN, select 5 sec gate
time if required and adjust VC2 through the front panel for the correct reading ± 2 ppm.
Select internal count and remove the frequency standard.
Dial fully clockwise, 5kHz range, note the reading on the internal frequency counter.
500Hz range, adjust VR12 for one tenth of the above reading ± 5 digits.
5kHz range, adjust verniers for 5Hz.
50Hz range, adjust VR36 for 00·05.
Fit shorting link to TP1 and adjust the verniers for 18·0Hz on the external counter.
Adjust VR37 for 1·80 on the display.
Remove TP1 short.
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