Electronics > Repair
HP/Agilent/Keysight Switching Power Supply Controller Repair
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ZGoode:
I removed the soldermask from the board which ended up making reverse engineering a lot easier.  There are 29 resistance sections built into the substrate.  The 5 smaller capacitors are 10nF (unsure of voltage rating) and the 2 larger ones are 100nF (also unsure of voltage rating).  Based on the 4wire measurements I got this should be fairly easy to reproduce.  I still have not been able to track down suitable modern alternatives for the transistors, but the diode pack is still produced.  And the UPC1042C is still readily available on eBay.

For the PCB design, I tried to keep the layout similar to the original to make it easier to verify if the connections are correct
coromonadalix:
wow  kudos for your work,   it means you'll be able to work an pcb substitute ...
Harry_22:

--- Quote from: ZGoode on January 28, 2024, 10:16:52 pm ---... and am 99% sure I have narrowed down the problem to this sub-board on the main power supply assembly.

--- End quote ---

Hi!

Of course everything you do here is very interesting.
But very often the malfunction occurs in the remaining 1% of which we are confident.
You could check sub-module with a datasheet on NEC uPC1042C. And if there is a problem then most likely this is it.

Have you found any faulty components?
ZGoode:
You are probably right that the UPC1042C is the likely culprit here, but the ceramic module is a pain to work on, so that's why I wanted to make a PCB replacement.  The transistors and capacitors test fine, so it most likely is the UPC1042C
Harry_22:
Work can be parallelized. Restore the ceramic module and make a new one.
Used NEC controllers are still available on Ali for pennies.
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