Re: PG506 standard amplitude output rise-time?


Albert Otten
 

That's true Siggi, but it doesn't explain the presence of C315 0.22uF across the output.
The 10V-and-below goes down to 0.2 mV. At that low amplitudes spikes produced by the switching power supply appear in the output signal and can be larger than the signal amplitude. I guess C315 serves to reduces these spikes. In earlier versions there was no C315 but the output was filtered by an LC network in the path to the BNC connector. The filter was by-passed in the 20-50-100V positions.

Albert

On Thu, Jun 13, 2019 at 11:51 PM, Siggi wrote:


The standard amplitude output is driven in two different ways - the
20/50/100V output is voltage driven with a current limit, whereas the lower
voltages are current driven for a 50Ohm load. There's a discussion of this
in the Theory of Operation section.

On Thu, Jun 13, 2019 at 1:58 PM Adrian <Adrian@nicol1.org.uk> wrote:

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



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