Electronics > Repair
HP/Agilent/Keysight Switching Power Supply Controller Repair
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ZGoode:
Howdy Y'all,
I'm working on repairing a broken HP 4277A LCZ meter I picked up a few weeks ago and am 99% sure I have narrowed down the problem to this sub-board on the main power supply assembly.  The part number in the service manual is 1813-0255 and there is practically zero information on the internet about the sub-assembly.  It consists of a 16 pin DIP, 3 SOT-23 components, and a few jumpers and capacitors.  I have identified the DIP as a NEC uPC1042C.  I am pretty sure about the SOT23's but not 100%.  The SOT23's are marked as A3, Y24, and L5.  I believe these three parts to be a 1SS181 diode, 2SA1461 PNP, and a 2SC1623-L5 NPN respectively.  It also appears to be using some kind of ceramic substrate material instead of something like FR-4, something I have actually not seen before.
Has anyone here replaced this component before or worked on a piece of equipment with a faulty one of these?  From what I can find is there are several pieces of equipment from this era of HP equipment that use this subassembly.
Swake:
That is a power supply switcher chip. Search for application notes, with a bit of luck you'll find something very equivalent to the module.

Similar ceramic boards can be found in philips tv's from the same era. Somewhat fragile, can't solder stuff on it as far as i remember. Philips used to have resistors 'printed' as a layer on those boards then coated with black paint.
coromonadalix:
yep  reworking on theses are almost impossible
ZGoode:
So far I have been able to successfully desolder the parts without visually damaging anything (might be damage I'm not able to see).  I'm planning on X-raying it sometime this week to get a better idea of what I am working with here.  The one good bit of news I can see so far is that all of the SMD parts on the board appear to be off the shelf, with the only proprietary part being the ceramic board itself
ZGoode:
So I made some progress on the internal imaging of the board today.  I took some images using the Keyence VR and SAM.  I'm planning on doing another pass with the SAM to see if I can clear up the image a bit.
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