Re: FG 504 function generator odd behaviour


Colin Herbert
 

Yes, Dave. I did indeed check and slightly adjust the +15 V and -15 V rails
some time ago. I also checked the +25 , -25 and +5 V supplies and had a go
at checking ripple using the differential method in the Service Manual, but
I didn't really comprehend the ripple results at the time. I should say that
this didn't cause the odd behaviour, it was already there and I was
attempting to solve it. I suppose I should have another go at looking at the
supplies, power rails and ripple again...
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Dave
Daniel
Sent: 10 July 2020 18:13
To: TekScopes@groups.io
Subject: Re: [TekScopes] FG 504 function generator odd behaviour

The first thing to do is measure the power rails to make sure that the
voltages are in spec and clean.

DaveD

On Jul 10, 2020, at 13:04, Colin Herbert via groups.io
<colingherbert=blueyonder.co.uk@groups.io> wrote:

I have an FG 504 which is showing some odd behaviour. The triangle-wave
shows asymmetry in that the negative peaks of the wave are rounded-off at
any frequency and the positive ones have a similar but lesser problem at
higher frequencies. This also seems to manifest itself as what looks like
cut-off on the negative peaks of the sine-wave and lesser cut-off on
positive peaks. While the triangle-waves are more-or-less symmetrical, the
sine-waves are definitely not so, showing a nearly three-to-one voltage
ratio in favour of positive peaks. There is also noticeably overshoot on the
square-waves at anything above 1kHz and only a DC offset at frequencies
below 80Hz.
I am totally ignorant of how this function generator produces
triangle-waves, but I do understand that the square-waves and sine-waves are
derived from the triangle-wave. Does anyone have any help that they can
offer? I would be grateful to get this useful function-generator working
properly.
Colin.


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