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A broken HP 33120A

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vaualbus:
I've recently bought a broken HP/Agilent 33120A with the stable reference in function generator for around 200 bucks.
Yesterday it arrive home, I turn on and for like 5 minutes it turn on and fail self test.
Than the fuse blowed.
I open the instruemnt and I've found a shorted diode CR704 a broken diode CR803 and four tatalium caps burned (one have also demage the PCB unfortunally).
I post some photo of the main board.
What I think it happens is that tese caps burn and take down the two diodes. (Strangly one of the two diode is cracked but still test good meanwhile the other is a short circuit).

Image 1: https://www.dropbox.com/s/gqvwzb979m0lru9/1.jpg

Image 2: https://www.dropbox.com/s/gzpujw8xk2i8vby/3.jpg

Image 3: https://www.dropbox.com/s/l8j6m6ntb0uubah/6.jpg

Best regards, Alberto.

vaualbus:
I have some problem with dropbox either on my machine or on the server. For now only the first image is  visible.

HighVoltage:
Can you tell us what the error message was during startup or selftest
I also have one 33120A that is dead but the problem is not clearly to be identified

vaualbus:
I can't now the instrmwnt doesn't turn on. I need to replace the csps and diodes.

pgross:
Is the fried tantalums in your 33120A - 20V rated types?

I know that a couple of 20V rated tantalums in the 33120A are mounted directly across the +/- 15V rails.

It almost looks like the same issue with the 34401A multimeter, where some have discovered 20V types
tanatalums have fried and damaged the pcb.

If the “normal practice” of min. 50% voltage derating should be applied, these tantalums should be
retrofitted to 35V types.

Hope that you’re able to clean / repair the pcb, and get it functional again.   

Best Regards

Peter






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