Re: LiteOn PA-6601-1A (600w) blows its TOP

Hi godonr, Q856 is on the underside of the board, it's a small SOT-23 surface mount transistor, my guess is that when the TOP blows, it can cause a surge of voltage to damage the Q856. Also in my case, the surge also damaged OPTO851. I couldn't get the exact repalcement, but it seems fairly standard in specification so I fitted one from my spare parts which had the same pinout.

So after replacing U801, Q856 and OPTO851, I have a fully working PSU.

Hope you have the same luck.

Cheers

Jon...

Re: LiteOn PA-6601-1A (600w) blows its TOP

I've just had one of these in to repair as well. U801 (TOP249) blown it's top, I checked C852 (47uF/25V); it tested OK, but I replaced it to be on the safe side. Powered up, and nothing!
I removed the board, and then did some more investigation. I have located transistor Q856 (MMBT2907A) which had gone open circuit between base/emitter, and short circuit between base/collector. I have ordered a replacement, no other components seem faulty. I'll update this once the new transistor has been received and fitted.