| Electronics > Repair |
| Help with dead AT PC Power Supply |
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| naujoks:
Here I have a dead AT power supply from 1994. I'd like to fix it, because the slim line form factor makes it quite rare and it lives in a nice pizza box PC case. I'm not getting any power output at all. I identified a faulty double diode S30SC4M, which had a dead short on the right hand side, it was therefore shorting the +5V rail. That short disappeared with a replacement diode, but still didn't give me any power output. There are no blown out or burnt parts. I checked the electrolytic caps. The MOSFET that lives to the right of the S30SC4M is also fine, so is another double diode that is in above the S30. Then we have two power regulators for -5/-12V (fine). There is a number of mystery components in shrink warp on the very top in the middle of the picture. I don't know what's on that board. I haven't discovered voltage regulators for +5/12V, could they be in there? The components seem to be too small for that, also they're not on a heatsink. The primary fuse is ok. There are two RIFA caps, which for the moment are not cracked (can I take them out of the circuit without replacements, for now). What would be the procedure to test for faults from here? |
| Harry_22:
Hi! You have to find PWM controller, find a datasheet and check the supply voltage. But seems the controller is on separate black PCB. Could you provide PCB bottom as well. |
| naujoks:
Picture of the back attached. Is the PWM generating the +5/+12V? |
| naujoks:
PS: I've taken the thyristor out for testing, that's why there's three empty holes on the back. |
| wasedadoc:
--- Quote from: naujoks on October 07, 2024, 01:36:02 pm ---PS: I've taken the thyristor out for testing, that's why there's three empty holes on the back. --- End quote --- Thyristor? |
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