Re: 2247A PSU Troubleshooting

Nicholas Keller

Thank you, Alex. This must have been the suggestion I saw here not too
long ago, I just got the impression that the diode list was an abridged
tally of what “should” be checked and replaced. When I pull the board
again, I will check these diode markings. Unfortunately I can’t test for
ripple yet as there is no power getting to the supply rails. I’ll report
back when I’m able to make some progress. Thanks again!


On Tue, Oct 23, 2018 at 8:09 PM <tekscopegroup@...> wrote:

I have a 2247A myself, excellent GP scope.

One of the first recommended things to do I was told is replace all the
rectifier diodes in the A18 LV power supply that have ZM or ZS markings on
them as they are well known to get leaky after "some time" (quoting the
very knowledgeable person that sent me this recommendation). Replace these
diodes with MUR160 600V 1Amp, you easily get them at Mouser, Digikey, etc.
On my scope all of them had either of the above suspect markings, so just
to be safe I replaced all of them. Whole procedure takes maybe an hour or
two, your mileage may vary.

Of course for an instrument this age, needless to mention to also check
filter caps, specially if you see higher than normal ripple on any of the
supply rails.

Suspect diodes are Tek PN 152-0400-00 (total 17 diodes) with alternate PN
given as MB2501. These are the on-board part locator numbers:

Hope that helps.

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