Hi PC hardware experts,
I use an old HP Compaq DC7700 Small Form Factor
desktop PC and a few days ago I accidentally left it running overnight (which I know should not be a problem, and it has been fine before), but the next day I went to use it and nothing was working, even after powering it off/on - not even a fan or light worked (not even the mother board light).
I think this is a power supply issue, because:
- I changed the mains lead - no go.
- The power supply fan doesn't even move (but I tested the fan by taking it out and feeding it 12V and that worked).
- I took the power supply out, and after watching some YouTube videos, I used a paper clip to short the green wire on the 24 pin connector to the adjacent black wire, but the fan still wouldn't go.
It may be not "worth" it, but if I can fix this power supply, I'd like to. Could be good for experience, too.
Having inspected both sides of the power supply circuit board, I can't
- bulging or leaking capacitors
- discoloured looking resistors
- dry looking solder joints.
I've tested that 236V (which is around the official mains voltage here in NZ) is getting through to the resistor which is close to where the mains comes in (just past the yellow rectangular component).
However, when I check for voltage across the long black component (presumably a fuse in shrink wrap?), I get nothing!
I also tested the resistance of that fuse (?) by unsoldering one end of it, and it's near 0, so I guess it's fine.
Q1. Should I have seen voltage when I measured across that long black component that looks like a shrink wrapped fuse?
Q2. Would that long black component be the fuse?
Q3. Can you suggest any other things I can test with a simple multimeter to isolate the culprit?
Q4. Can you suggest any other components that either look suspect or are likely candidates? If so, how can I test them?
See photos attached. (Sorry they don't show everything and some are a bit unfocused. Let me know if you want me to take more.)