Help me repair an Amiga power supply?

[Hodgkinson]

I fixed a SMPS in a 24-port network hub some time ago. The large beefy 100K or so resistor from the rectified mains side at ~300v DC had gone open-circuit [cooked, charred, and falling to pieces], and in the process it had caused the controller IC (A small 8 pin DIP IC on a sub-board) to go short circuit across what appeared to be it's supply pins.
Replacing the resistor with a even larger (Higher power) resistor and swapping the controller IC did the trick.

PS. Phihong power supplies in the US are extremely helpful with regards to fixing their power supplies - BOM, circuit diagram, etc, can't praise them enough.

PPS. The other common failure is the power devices going short circuit.
EDIT: Oh, you've already swapped them :-)

Just thought I'd point out some of my experiences,
Hodgkinson.

[Hodgkinson]

Dang, I'm ringing you up the next time I'm working on something. I'll probably save a day or two.

:-) :-D I'd be glad to help

[Hodgkinson]

Hi there,
I’m afraid my knowledge stops there, too. The only reason I managed to fix my SMPS was because I could see visual damage.

I've had a word with a electronics engineer, and the best advice that we can give you is to try loading the PSU outputs, and to go around and check the resistance of all of the higher valued resistors (>=100K) by unsoldering one leg of each resistor and checking each one in turn - The higher valued resistors have a tendency to commonly fail by going open circuit.

Regards,
Hodgkinson

[Hodgkinson]

Glad to hear that it’s working :-)
I guess the winding was short/open circuit? You're lucky that you were able to spot it - It only takes a single turn of a winding to short out in an EHT transformer and that'll stop everything dead - And an ohms meter won’t pick it up.

:-)

Hodgkinson.