I don't trust power supplies over 10 years old. The AT era ones are just too risky to the increasingly rare parts inside, and to general system stability. I use modern supplies with a connector adapter, and that gives me much better voltage quality, short circuit protection, and a quieter fan.

It sounds like you have a hard short of some kind. Check to make sure that all plastic risers are in place, that there are no extraneous metal standoffs, and try the power supply without the system connected to it.

My board has an ATX power adapter on it, and I have a 550W power supply. I’m guessing there is a jumper for switching to it?

Could this be the result of incorrectly plugged in power connectors?

They need to look like this FYI... I don't recall if I've ever owned a board that had both AT and ATX power connections. Didn't think they existed but I am getting old, so....

a complete parts list of what you have might help too.

Note the order of colored wires.

I checked that image before hooking it up so I’m pretty sure it was correct.

I tried the board with an ATX power supply and I’m getting clicking seemingly from the PSU. I’ve attached an image of what it looked like for a sanity check.

I have had an issue like this before as well with my ATX-power supply; when I turned it on I'd also hear a ticking noise.
It turned out that my 4-pin cable wasn't installed correctly. So I'm guessing you've got a connection issue, though it seems you have installed everything correctly. Maybe there is a broken connection in either the cable, power supply or motherboard?

The ticking sound is usually due to the power supply refusing to start because there's something shorting to ground. It is probably also why the AT PSU caused the fuse to pop.

Start by checking resistance with a multimeter in the power connector of your motherboard between the different power rails and ground, you may find a short there.

Strahssis wrote:

I have had an issue like this before as well with my ATX-power supply; when I turned it on I'd also hear a ticking noise.
It turned out that my 4-pin cable wasn't installed correctly. So I'm guessing you've got a connection issue, though it seems you have installed everything correctly. Maybe there is a broken connection in either the cable, power supply or motherboard?

I don’t have the 4 pin plugged into anything. I thought I just needed the 20 pin at minimum.

TheMobRules wrote:

The ticking sound is usually due to the power supply refusing to start because there's something shorting to ground. It is probably also why the AT PSU caused the fuse to pop.

^^this. I'd focus anywhere else but the PSUs

The shorts. Good Lord.

I have this compaq this 386. (see pic) Fuse inside PSU shorted.Replaced it ,and obviously shorted again.

Had the great idea to replace it with a piece of metal (sigh and 🤣) . PCB traces from fuse to PSU mosfets MELTED and sparkled into a fiery plasma fire. Magic smoke everywhere.
That's when i've learned about checking ALL main PSU components, and if there are shorts on the board,well, you have to replace that component...

Found that the bu-508 (main mosfet of that PSU) was SHORTED between base and emitter (NO POWER IC'S should have shorts between 2 of their 3 pins!) Replaced it with a similar one from a scavenged Television power supply and the 386 worked again!!

I don't know what's the origin of your problem, but be careful when using old PSU's!

If i may help you:
1. AT PSU. Check it barebone. Nothing attached.Switch it on. if it works and fan spins: Mobo problems, or peripheral problems.Then try with only mobo, and eventually plug all your isa cards one by one.
2.If AT Psu shorts immediately, check for swollen capacitors and shorted Power IC's (mosfets an voltage regulators) on the power supply board.

Another method for the AT PSU: buy an ATX-AT w/ -5VDC and dummy load (3.3V) and use a new ATX PSU instead. As for the shorting issues, check the traces and solder on the motherboard, especially capacitors, resistors, and so on for anything out of the ordinary.

Dog wrote:

I don’t have the 4 pin plugged into anything. I thought I just needed the 20 pin at minimum.

I know you haven't, but that was not what I was saying. I was saying that I think you have a connection issue between the motherboard and the power supply of some sort. Please refer to the other posts; I think those might help you fix the problem! 😊

fitzpatr wrote:

I don't trust power supplies over 10 years old. The AT era ones are just too risky to the increasingly rare parts inside, and to general system stability. I use modern supplies with a connector adapter, and that gives me much better voltage quality, short circuit protection, and a quieter fan.

It sounds like you have a hard short of some kind. Check to make sure that all plastic risers are in place, that there are no extraneous metal standoffs, and try the power supply without the system connected to it.

I read this yesterday and Motivated me to swap out the AT on my 386 to a new ATX I got with a converter, some very good points there. Going to do the same on my 586 system too.
Did you wire up your power button to the atx connector direct? The original power plugs on the case have 4 pins but the ones on the atx converters have 2 plugs, does it matter where you plug them on the switch or just find a combination that will close the circuit and start the system?

Also for me personally I had the ticking sound happen in 2 scenarios before.
1. power. cables in the wrong way
2. cpu in the wrong orientation on the socket (486)