Is the power supply fuse blown?

Also that big cap by the black wires looks kinda off.

DankEngihn wrote:

Is the power supply fuse blown?

Also that big cap by the black wires looks kinda off.

I checked the fuse...had continuity across it.

I think it's just the light making the top of that cap look like that. It's not bulged or discolored in-person.

Interesting power supply. More or less an AT with +5vsb added.
Your symptoms suggest a problem with the +5vsb.
[Speculation because I haven't seen that type, least not in recent memory.]
= The 3 wires would seem to be.
Ground [duh]
+5vsb to the system. (Power to the front switch whenever the PSU has power to it.]
Power from the switch back to the PSU telling it to turn on or off.
-
(Before it goes there... Not all bad caps bloat..)
Most likely suspect is the main cap in the +5vsb circuit.
It has power whenever the PSU is plugged in so it 'felt' the power surges and would have tried to suppress them.
If it is shorted then your front switch isn't getting power except maybe for a short burst when you first plug it in.
They are usually 6-8mm caps at ~47uF and 35-50v but it does vary.
If that isn't it then look for something else in +5vsb. (Small caps and small transformer in vsb first.)
The large input caps can blow too but surges don't kill them as often as they kill vsb caps.
.

I have a Delta 145w AT power supply I use on my test bench that came from a dead Acer using that same three pin plug to turn it off and on. Check out Delta DPS-145PB-50, though I don't know weather it will fit your machine without modifications. I jumper wire the white and black wires together in the P7 connector to start the power supply, and pull jumper wire to turn it off.

Edit: I looked though old web pages on that Acer I saved. Saw someone mention fitting a Compaq Mitac MPU-110REFP as a replacement. It has an on off switch right on back, not sure of exact external dimensions compared to your unit though there are some on ebay. May be worth checking out.

Thanks...I'll look for failed component(s) on the +5vsb circuit. I'm not super skilled with that stuff, but I have successfully replaced (obviously blown) caps in both of my //e power supplies, so I can likely figure it out 😀 It'll probably be a couple weeks or so before I have time to mess with it...I'll post updates when I do though.

I never was able to revive this PSU. Question...how would I go about using an ATX PSU with an adapter, but keep the momentary power button on the front of the case working? Also, would I need to worry about the lack of -5V?

You can do this with ATX adapter and splice 3 wires to this 3 pin plug. The 3 pin connector is ground, standby 5v and other wire is power on signal by grounding it.

What you need is know the pinout of the 3 pin plug.

Cheers,

pentiumspeed wrote on 2020-03-10, 03:06:

You can do this with ATX adapter and splice 3 wires to this 3 pin plug. The 3 pin connector is ground, standby 5v and other wire is power on signal by grounding it.

What you need is know the pinout of the 3 pin plug.

Cheers,

From looking at the labeling on the dead PSU's PCB, I believe the pinout for the 3pin plug is black=GND, white=ON/OFF, red=+5V. So, from looking at a pinout for a 20pin ATX plug, does that mean I would splice the wires like this?

• connect 3pin plug's black wire to any black wire on the ATX plug
• connect 3pin plug's white wire to the green PS_ON wire on the ATX plug
• connect 3pin plug's red wire to the purple +5VSB wire on the ATX plug