Electronics > Repair
Help Identifying missing 0402 capacitors
(1/1)
AstutePauciloquent:
Hi everyone, I have this older Geforce PCX Albatron 5750 with 3 missing 0402 capacitors that I need help determining their value. Yes this is an old card that is not really worth anything, but the reason for doing this is purely for the fun of learning, and making something work again, and as far as i know this card was purchased years ago and it arrived faulty so its never been used. Apart from when i tested it (it posts, but locks up the system, after 5 seconds). I have the tools, skill and knowledge, including a microscope in-order to solder the replacements caps on. As ive been able to remove and reattach these tiny caps in order to measure their capacitance.

I know the basics of how to read schematics and I have boardview software, however im not able to locate such resources for this card. I’ve tried looking at similar types of cards in boardview software, but everything is just to modern compared compared to this.

I’ve read somewhere that its probably ok to just attach some capacitors that are similar values to the surrounding ones, but how true can that really be? these are located on the back of the card. I have included to images, one being a close up.



MathWizard:
They might be for a chip on the other side of the PCB, it might be for some high speed serial chip for the PCI-E bus.

If you could narrow down what circuit the caps were from, with a DMM, like a local Vcc supply cap, or part of some RC sensing network like for a step-down regulator, or just a DC blocking cap for some AC signal path. If it was for some near by chip, it might not be that hard to guess a rough value, or find a similar value in a datasheet example circuit.

There's always some risk that more damage could be done I suppose, but you could just try 10nF caps, and see if it runs then. 100nF caps are probably the most common on the whole thing, for all the Vcc lines to all the IC's.

On the 2 GPU's I've tinkered with, there weren't that many sub 1nF caps. Actually iirc one of them is an AMD/ATI HD5770. It's overheating, IDK why, the fan works, but it does make it into windows, before overheating. I've ordered a good Logic Analyzer, but it's stuck in the mail. But yeah now that I know a bit more digital stuff, I look forward to tinkering with that again.


I would try my best to find what circuit it's part of, so what is it connected to, and what are they connected to, then guess a size, but 1 or 10 or 100nF would probably get a lot of circuits working. If needed, I'd solder some thin wire to those pads, then tape or glue the wires down, then go around trying to find, if possible, it might not be, where those caps go.
usagi:
Try 100nf, it either works or it doesnt.
little_beast:
good luck :)
Navigation
Message Index
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod