exxos's Atari, Amiga & retro forum

Well I've recently reassembled my STE after a full recap, given it a few nights of playtesting so I seemed it healthy enough to have the screws put back in. Obviously next time I switch it on, there's a problem.

Output seems fine with the switch open, but drops drastically when on.. the 12v was showing ~4 and the current ~0.5

It's a Phihong.

I've checked the diodes around the board, the one closest the output - D8 appears to be shorted, so obviously needs changing. I'll change them all, would you expects recommend anything different to the factory fitted?

Anything else obvious I should try? Like I say, i have recapped the motherboard as well, and while i did wash it and inspect quiet thoroughly, I can't rule out the motherboard as I don't have an immediately handy alternative PSU

Please post a image of the power supply so we can double check things look correct.

It looks correct, can you post a image of the bottom of the PCB..

Also do you have a load on this power supply as they will malfunction if not connected to anything..

I've not got a load on them no, and I don't want to use the motherboard at the minute, I'll be buying some load resistors from your shop soon.

I can see I need to rework those joints. I've since upgraded to a much more powerful iron, the old one struggled on this chunky board.

I guess these are the original caps? The solder on the pads of the small capacitor next to the three resistors looks really bad, same for the larger caps. It's very dark. If caps leak sometimes the fluid can degrade and eat away at the solder.

No the caps are new, as I said my iron wasn't powerful enough, and I think that reel of solder I used was lead free. I know I need to heat flow those again.

I can't seem to find much about that diode, what would be a good replacement?

curlypaul wrote: 08 Jul 2021 21:21 I've not got a load on them no

Then any voltage testing you do is irrelevant .

curlypaul wrote: 08 Jul 2021 21:43 I can't seem to find much about that diode, what would be a good replacement?

Again at this point irrelevant as you haven't tested the PSU properly to even know if something is wrong or not. Plus diodes should be removed and tested before looking for parts you may not actually even need.

Well I got those brief readings from the 12v line when loaded with the motherboard, so they seems like there is a problem.

I thought the diode test function on the multimeter would be fine while connected, and it was just the resistance test that needed them off. I'll desolder a leg to double check though

Thsnks

Looks like I missed my load resistors arriving today, but I've reflowed and cleaned all of this, and as you pointed out, that diode seems fine once disconnected.

I'm a but happier showing off this soldering job compared to the last one.