TheMobRules wrote on 2022-08-23, 15:42:

The PSU is ATX right? First thing I would check is if you have 5V on the standby line (purple wire usually) when you flip the switch. If there's no voltage at that point then probably there's a short somewhere and the PSU is in protection mode, in some cases you can also hear a high pitch sound and/or the fan tries to spin up for a second.

Carefully go over each joint you soldered, also checking the capacitor orientation, post pictures if you're not sure. Also look for solder blobs that may have spilled over parts of the PCB.

Regarding your earlier question about the big caps, it's strange, I never had issues soldering these at around 350C or even with a crappy 40W iron. Besides, it's a single sided PCB, I don't think it would sink a lot of heat compared to a motherboard for example. Maybe your iron was oxidized or not making proper contact with the pads/legs?

Yeah its an ATX psu , a dell NPS250KB.
The room I'm working in is in the back of my house and there's no heating there and its pre cold like under 10 degrees Celsius , maybe that's why the iron is having trouble?

Here's a picture of the back in case anything stands out.

Also does anyone else with the same psu have a layout diagram of the caps? , I just want to compare it with mine in case I put any caps in the wrong area.

Uh so you won't believe this the psu started working i hit the test rigs on button , and It magically came to life , it read 11.87 on the 12v rail and 5.06 the 5v rail.

I managed to unplug it and plug it back in and it worked

but get this

after I unplugged it and came back after a while and plugged it in and pressed the on switch it was dead again. Really strange stuff.

Any ideas on what the heck is going on with this weird psu?

you might have cold solder joint somewhere. You need a good light source, some magnification and wiggling wires/components while looking at an angle to spot it

Okay so you wont believe what I found i dunno how i didn't notice this before but the pcb has a hairline fracture and the resistor under the primary caps is completely cut off , I'm also worried about the main power track above it which is half severed.

Could I just use solder to bridge the traces along with nail polish to cover it? Also is there anything I can do to mitigate the pcb having issues with further cracking and trace splitting in the future seeing as the pcb has a bit of a localized flex to it?

Drill a small hole at the end of the crack to keep it from cracking further. Patch the traces with solder. Use a nice thick layer of solder especially on the thicker trace .
You could add wires across the cracks to give it more strength.
You could add some super glue from the top side along the crack to make it even stronger.

DerBaum wrote on 2022-08-26, 09:02:

Drill a small hole at the end of the crack to keep it from cracking further. Patch the traces with solder. Use a nice thick layer of solder especially on the thicker trace .
You could add wires across the cracks to give it more strength.
You could add some super glue from the top side along the crack to make it even stronger.

Well its not super pretty but I managed to bodge it up , ill try adding some super glue on the cracks to hopefully give it some extra strength , I just hope the glue can cope with high temps that might be inside the psu when it runs and not melt.

imo you didnt scrape enough soldermask off before bodging those tracks together. A good 2-3 milimeters each side is a good amount + wire across.

rasz_pl wrote on 2022-08-26, 10:59:

imo you didnt scrape enough soldermask off before bodging those tracks together. A good 2-3 milimeters each side is a good amount + wire across.

I mean you're probably right , I did scrape a teeny weeny bit from both tracks with a scalpel but I probably should go back and redo it , I'm not sure if I have thick enough wire for the big track though , but at some point I should add some bodge wires.

Nevertheless at least for now it appears to be working! 😁
Man that was an adventure , and an insane amount of hair pulling and troubleshooting , I don't think ill want to recap a psu ever again.

With all this experience under your belt now you cant not recap more 😀

rasz_pl wrote on 2022-08-27, 10:18:

With all this experience under your belt now you cant not recap more 😀

Well I should never say never xD.

Also , a bit of an update
the smaller track lost continuity again so I got fed up and used a capacitor leg wire to bodge the gap , I also broke off a peice from a fuse holder on a scrap pcb and used that to bridge the bigger trace.
So hopefully it should be reasonably secure now.

👍

I threw it back in the rig and it seems to be working quite well , no weird restarts anymore.
Phew , I'm pretty chuffed