The 1kHz standard amplitude waveform was a curious shape, traced to a dead or dying opto-coupler driving the 'standard' amplifier stages, fixed by replacing it.
I then noticed that the output waveform rise time was noticeably faster (~1us) at outputs of 20V and above than at 10V and below (~23us) this seems to be due to the 0.22uF in parallel with a 10k5 resistor that is present across the output connector when these lower voltage ranges are selected.
I realise that this doesn't really matter as it is the amplitude accuracy that is important in this application but I have failed to find mention of the purpose of this filter in the service manual, can anyone enlighten me?
Thanks in advance,
Adrian
