Just get a multimeter and map out which connection points on the switch are linked when the switch is in the powered on state.

If you don't need to mess with -5V, my setup is a modern ATX power supply with an ATX -> AT adapter. That includes two cables that when connected causes the PSU to power on. I wired connected those to the rocker button. Less worry about 35 year old power delivery hardware.

Thanks! Yes I have tested continuity with a multi-meter, but I wanted to be certain I wasn't missing anything. Tripping household fuses is one of my lesser popular pass-times.

Good point on the modern PSU, I do have some adapters laying around but I didn't think of that for this use-case. I'm using a later gen SB16 in this build so I shouldn't have any concerns about -5V.

After doing a bit more reading on this, I may have stated the wiring incorrectly. If I understand correctly, in a closed circuit, the two black wires will be connected (live) together, and separately the white and the blue will be connected (neutral). So looking at the back of the rocker switch with the plastic divider running vertically I think it should be:

Left Top Black
Left Bottom Black
Right Top Blue
Right Bottom White

Is this correct?

The more I read about this, it seems using the old AT PSUs is inherently more dangerous that an ATX PSU. I think I'll pick up an ATX PSU and install that.
The ATX to AT cable I have laying around has two green wires with spade connectors for a switch - does this require a momentary switch, or can I use the rocker DPST on the case?
Thanks!

JayAlien wrote on 2026-11-06, 12:30:

The more I read about this, it seems using the old AT PSUs is inherently more dangerous that an ATX PSU. I think I'll pick up an ATX PSU and install that.
The ATX to AT cable I have laying around has two green wires with spade connectors for a switch - does this require a momentary switch, or can I use the rocker DPST on the case?
Thanks!

It needs to be a latching switch like the rocker. ATX power supplies ground a sensing line to power one, and must keep it grounded or it will power off.

Connecting those two wires to your rocking switch will make it work without issue. The only problem with is the screw holes changed from AT, so you'll generally only have two or three points to mount them rather than four. It's not really an issue though.

Very odd - I've got the new ATX PSU in, wired the two additional wires (one black, one green) to my rocker switch, but no power when flicking the rocker switch.
Checked everything - all seems in order. What am I missing?

JayAlien wrote on 54 minutes ago:

Very odd - I've got the new ATX PSU in, wired the two additional wires (one black, one green) to my rocker switch, but no power when flicking the rocker switch.
Checked everything - all seems in order. What am I missing?

If you connect the two wires by hand does it power on? Also make sure the switch on the back of the PSU is turned on if you didn't already check.

Thank you SScorpio. I think it's about the time of year for my annual reboot.
User error on my part. The ATX connector on the power supply is a 24 pin, not the 20+4 I'm used to, and additionally all the cables are black, leading to late-day disorientation. I'd like to blame these two factors, and of course not myself, for somehow plugging the ATX to AT adapter into the new PSU incorrectly. I've rectified my mistake and the computer boots perfectly.
I'm using up the limited lives this old board has.
Thanks for your assistance, I appreciate it.
J