Good day folks. It's been a while since I've fixed a PSU and it shows with this one, as I can't seem to figure out how it works and what's wrong with it.
Fuse was open (though not obliterated) and the two transistors shown were shorted. The originals pictured up-close are AP50WN1K5I and I couldn't find the exact match. They looked pretty standard in terms of specs, so the guy at the store looked over some datasheets and gave me two FQPF6N60C instead. The datasheets are indeed pretty close, except the replacement ones are a bit more resistive. I though it wouldn't be a deal-breaker and would work first-try...unfortunately it didn't...
No catastrophic failure occurred but I got no boosted voltage on the main cap (stuck at 325v) and I got no output at all...after trying it a second time, I think I saw some smoke coming out. I couldn't see where it came from, since I quickly unplugged...I managed to quickly measure the AUX winding to see if the control IC, a TEA19161T gets VCC, but the winding is dead....
I measured the gate drive portion of both trannies and ironically everything checks out fine, so again, it could be that smoke was just my imagination, ALTHOUGH: I removed the trannies again to see if they died and the answer is "sort-of", meaning they're not dead-shorted, but one of them measures weird. Get this: I put them side by side and used my meter in diode-mode:
Should I bother to replace the TEA control IC ???
This is a strange PSU: it's only got a 12v output, yet it still has a green "PS_ON" wire.....how does this work ? The yellow wires are all bunched together, so how can there possibly be a "stand-by" voltage ? Even if 12v WERE the standby voltage and were on all the time, what's the purpose of the green wire then ??? It could be it's just the color that's similar, but in reality it could be a power-good signal...I was hoping I could replace the supply entirely with a 12v one, but it will be missing this signal and refuse to turn on......really sucks this one :|
Fuse was open (though not obliterated) and the two transistors shown were shorted. The originals pictured up-close are AP50WN1K5I and I couldn't find the exact match. They looked pretty standard in terms of specs, so the guy at the store looked over some datasheets and gave me two FQPF6N60C instead. The datasheets are indeed pretty close, except the replacement ones are a bit more resistive. I though it wouldn't be a deal-breaker and would work first-try...unfortunately it didn't...
No catastrophic failure occurred but I got no boosted voltage on the main cap (stuck at 325v) and I got no output at all...after trying it a second time, I think I saw some smoke coming out. I couldn't see where it came from, since I quickly unplugged...I managed to quickly measure the AUX winding to see if the control IC, a TEA19161T gets VCC, but the winding is dead....
I measured the gate drive portion of both trannies and ironically everything checks out fine, so again, it could be that smoke was just my imagination, ALTHOUGH: I removed the trannies again to see if they died and the answer is "sort-of", meaning they're not dead-shorted, but one of them measures weird. Get this: I put them side by side and used my meter in diode-mode:
- RED probe on D and BLACK probe on S gives me nothing (which is normal)
- RED probe on S and BLACK probe on D gives me 0.55v which is the body diode (also normal IMO)
- RED probe on G and BLACK probe on D gives me nothing on both of them, (which is normal). This should also "open" the D-S path...
- now, RED probe on D and black on S gives me 0.38 on one and 1v on the other one. THIS doesn't seem normal to me. I think the good one is the one with the lower reading.
- strangely, after "opening" the transistor again, if I go RED on S and BLACK on D, I get 0.1 on the "good one" and 0.2 on the "faulty" one.......what do you guys make of this ?
Should I bother to replace the TEA control IC ???
This is a strange PSU: it's only got a 12v output, yet it still has a green "PS_ON" wire.....how does this work ? The yellow wires are all bunched together, so how can there possibly be a "stand-by" voltage ? Even if 12v WERE the standby voltage and were on all the time, what's the purpose of the green wire then ??? It could be it's just the color that's similar, but in reality it could be a power-good signal...I was hoping I could replace the supply entirely with a 12v one, but it will be missing this signal and refuse to turn on......really sucks this one :|
Comment