That's wild... but yeah, I mean there's gotta be something more to simple thermal issues, right?
PluMGMK wrote: Fri Oct 31, 2025 8:24 pm
Sounds like an excellent plan! Are you going to use the Traco parts I talked about to produce the negative voltage rails? What about the PS_ON, will you wire that to an AT mains power switch?
So I decided to look into the power supply situation further, as I may be able to get away with a modern ATX power supply into an AT system, if I avoid Corsair, since Seasonic for example, seems to still support the -12V rail. From my understanding from one of your earlier posts, serial ports, aka RS232 rely upon this usually, yes?
Since I do often need to use a serial mouse on these old machines, the lack of that rail would be a bad idea.
And depending on the add-in cards, I may or may not need the -5V rail, which can easily be
restored by the methods I mentioned earlier or a similar to what you're doing method.
Also something I feel I need to clarify on:
I've also come to realize that earlier on, when you spoke about your negative voltage adventure, I cannot find the post to reference, but I realized I had initially confused the -12V rail with the -5V rail initially. Since I thought only some of the old ISA cards, like audio, networking, etc that did need it, would be missing it with a modern PSU. Except now we're in the same boat over the -12V rail from some manufactures, it would seem.
Either way, my new adventure begins with the
ATX to AT adapter I posted about earlier. Now, sadly I do not have the resources to easily get my hands on one of these
fancy adapters.
That being said, the reason for concern is the mere fact we're dealing with a high amount of current capabilities on the old PSU's, at least on the 12V side. Really not much has changed in the 5V realm, as PSU's then and now are the on average the same, but for example, one of the PSU's in my 486 rig can supply 8 amps max, where a modern PSU can easily reach 50+ amps... so obviously in the event of a short circuit, such as a shorted capacitor, well... more than likely the copper tracing on that motherboard is going to go up like a fuse since there's no way this low of a current will trigger an over current protection on a today PSU.
So I'm thinking the next best route is the small automotive minifuses, since I can get those in a fast blow. Something nice and small such as
this 5amp fuse.
I can either find an
in-line fuse holder and solder the wires together, and size the fuses to what the motherboard probably *could* pull max, with a few add-in cards, or even do a small automotive fuse block if that would let me fit those in place as well, such as
this style by Eaton (BP/FB4-ATM) which would allow me to cover the 12V line and even fuse the 5V lines each as well for added protection there. 'cause you never know!
Now we probably can assume the 5V rail is going to have a greater load on it, without a doubt on these old systems... Especially given how many dedicated wires there are for them each:
What do you think, PluM?
I'd love to get a damaged device under the SEM and see wtf is going on 
