A sawtooth ripple on the unregulated DC is exactly what you should
see -- the cap rapidly charges up when the rectifier forward biases,
but slowly discharges once the rectifier goes into reverse bias.
If the regulator always regulates, then that ripple is benign. That
is, ripple on the unregulated DC is to be expected. If ripple
doesn't show up on the output, then the regulator is doing its job.
--Cheers,
Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
On 2/20/2022 04:48, Jinxie wrote:
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Hi all,
This relates specifically to the 8566B but is no doubt relevant to
all analysers with linear power supplies.
My 8566B has been suffering from the infamous YTO ulock error and
it was suggested on some Youtube clip that it would be a good idea
to scope the power rails. To cut a long story short, I was seeing
ripple further down the line (in the direction away from the main
PSU section) so I decided to go back to the start and scope the
main storage electrolytics (you know, the big, beefy ones to use
the correct terminology). Anyway, they *all* have ripple on them
and it's more than I would expect, at around 10% of the DC
voltage. So for example on 12VDC I'm seeing just over a volt P-P
of ripple. Furthermore, it's not sine waveform either, but
saw-tooth! I did check these caps for ESR and capacitance some
time ago with my Peak ESR meter and they all came out OK as I
recall. So I'm not sure what to check next. Any suggestions? I've
got all the service manuals and whatnot on DVD but find it much
harder to follow what wiring goes to where without a proper
hard-copy book type manual to flick through. :(
