Re: Advice on HP Function Generator Repair


"Jake" <mechanicaljake@xxxxxxxxx> wrote in message
news:29dacea7-824e-4de6-bbd3-53a0203f5ef9@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
On Apr 15, 1:18 am, "Matt J. McCullar" <mccul...@xxxxxxxxx> wrote:
Not having seen a picture of the function generator, I'm presuming you're
using an external oscilloscope to look at the FG's output.

Just a question: Have you been able to verify that the strange waveforms
are
actually coming from the function generator itself, rather than an
artifact
of... say, the oscilloscope probe and/or the oscilloscope itself not being
able to handle incoming frequencies that high? Just don't want you to
waste
time trying to fix something that may not actually be broken. :)

If it is definitely coming from the function generator, then I'd agree
with
the previous posters: replace the electrolytic capacitors. They're over 20
years old now.

I am using a brand new Tektronix TDS2024B 200MHz 2GSa/s oscilloscope
with a fresh calibration.

Thanks for all the advice!

Not wishing to labour the point, but what you describe as happening to the
waveshapes, in that they are all heading towards a dirty sine wave the
higher up in frequency that you go, sure sounds like what you will get if
you glue a low-pass filter on the end of such a generator. Are you
absolutely sure that there is not any bandwidth filter switched in on the
'scope, and that the probe you are using is good for the frequencies that
you are looking at ? Is it a low capacitance probe for instance ? Looking at
anything above a few hundred kHz generally requires the use of a low
capacitance probe (typically a x10 attenuator probe, or a 'universal' probe
switched to its "x10" setting)

Arfa


.

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