Premier 300W blown parts - still works

[370forlife]

My friend gave this to me, it came out of one of his many computers. He said it made a popping noise one day and stopped working. I opened it up and didn't see anything immediately dead. I plugged it in and connected my little ultra psu tester, and it powered up and I double checked the rails with a dmm. Everything checked out. Hmm. It's not too bad inside being made by ATNG, so I proceeded to recap it and put some parts into it. Powered it up and it ran fine again.

Then I looked at the original CS brand primary caps and noticed some burn marks on them. So i started looking around on the primary side, and noticed a smoked resistor and a diode that looks like it had gotten hot and let the magic smoke out.



And when I took the primary heatsink out and noticed this on it



Not sure how I didn't notice that when I replaced the primary caps.

Guess these two parts aren't too crucial seeing how it can still run just fine with a blow diode and resistor on the primary. I'm just going to replace them anyways just in case it blows up when put under a higher than ~20W load added by that little ultra psu tester.

[370forlife]

Re: Premier 300W blown parts - still works

Ok so I pulled the resistor and diode out. The resistor was still good, it just got smoke damaged. Cleaned right up and that still works. The diode was a PR1007, so i replaced it with another PR1007. Powered it up and it checked out ok again.

I was tempted to replace both the PR1007's with PR1504's, but the 1007's are 1000V rated and they are always 1000V on these half bridge designs, regardless of the OEM, so I figured there must be a reason why.

[Wizard]

Re: Premier 300W blown parts - still works

1,000V bogus.

The highest this voltage doubler design can go is around 330V or so. Replace the 2 diodes (this is what doubles the 115V to this, and this 150K resistor (this bleeds the caps flat if there for safety).

Cheers, Wizard

[riotpack]

Re: Premier 300W blown parts - still works

They use 1000v PIV rated diodes so they can handle higher voltage spikes. Where there are inductors and transformers and rapid switching of these you can expect some untidiness on your B+ - also who knows whats coming in from the mains? My first stun gun project killed more of the UF4007s than it should have - I used 5 in series per bridge arm and they were only rectifying low voltage (around 600-1000VAC) but randomly they would die SC, may last 4 months before it happened but they did.