Re: FG 504 function generator odd behaviour


Colin Herbert
 

Oops! I have checked the voltages and while the +25V (+24.99), +15V (+14.98)
and -15V (-14.98) are just about bang on, the -25V is sitting at -3.58V. I
really can't remember if this was the case when I checked previously, but it
is now. I did manage to short something out with the DMM probes, so that may
have given this problem, but sure as sure it needs to be fixed, but how?
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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