I'm nowhere near the US so I cannot offer to attempt a fix, but one thing you should consider is getting a PCI/ISA POST card on eBay (they're very cheap). It will let you know whether the CPU is trying to execute BIOS code, which is an important first step when troubleshooting a board.

I second the recommendation for a POST card. It's one of the most useful pieces of hardware to have for troubleshooting older hardware.

do you have pc speaker connected? does it make any sounds?
try clicking numlock - does the keyboard LED change color?
Those two are tests meant to determine if CpU/BIOS is trying to run at all, the only thing you need to perform them is motherboard with CPU, power and keyboard connected, everything else removed.

TheMobRules wrote on 2024-01-26, 03:25:

...one thing you should consider is getting a PCI/ISA POST card on eBay (they're very cheap). It will let you know whether the CPU is trying to execute BIOS code, which is an important first step when troubleshooting a board.

It's only now that I hear about this actually useful utility... I'll get one when I can.

rasz_pl wrote on 2024-01-26, 04:34:

do you have pc speaker connected? does it make any sounds?
try clicking numlock - does the keyboard LED change color?

I probably should've mentioned that; no, I don't own a PC speaker to connect. After the initial flash of the keyboard lights, none of the keys seem to do anything; not even Num Lock.

you can get a post card with a speaker (buzzer) that solves basically all problems at once 😁

Just bought a POST card off of Amazon. That was the cheapest and quickest I could get one. (:
It has a piezo speaker as DerBaum mentioned:

DerBaum wrote on 2024-01-26, 13:55:

you can get a post card with a speaker (buzzer) that solves basically all problems at once 😁

As well as everything else that I think a POST card is supposed to have. (number display, indicator lights, PCI/ISA slots, etc.) Attached is a picture of the card I bought.
It's supposed to be here by the 31st. In the case that it gives out an error that I can't fix, (which, if it does happen, it will be a few days from now) does anyone still want to take a stab at repairing my system?

alexparr wrote on 2024-01-26, 12:48:

After the initial flash of the keyboard lights, none of the keys seem to do anything; not even Num Lock.

Keyboard initialization is right at the top (~10th routine) of bios startup sequence, so that means either POST fails very early, or your CPU is not running at all. Might be difficult to diagnose without spare cpu/motherboard.

>in the United States

You might want to either narrow it down, or look for HackerSpaces in your area, there usually is at lest one Vintage enthusiast hanging around a hackerspace 😀

rasz_pl wrote on 2024-01-26, 14:26:

Keyboard initialization is right at the top (~10th routine) of bios startup sequence, so that means either POST fails very early, or your CPU is not running at all.

I'm hoping it's the latter, as I do not want to spend upwards of $100 on a motherboard with a similar feature set to this one.

rasz_pl wrote on 2024-01-26, 14:26:

You might want to either narrow it down, or look for HackerSpaces in your area, there usually is at lest one Vintage enthusiast hanging around a hackerspace 😀

I have never heard of hackerspaces until now. Why am I suddenly finding out about these useful resources now?!

alexparr wrote on 2024-01-26, 17:07:

I have never heard of hackerspaces until now. Why am I suddenly finding out about these useful resources now?!

Its quite recent phenomenon. Makerspaces/Hackerspaces started showing up after 2005, thats when Maker magazine started publishing just after 3D printing became available to amateurs thru RepRap project and Arduino opened microcontrollers to laymen. When I was growing up in the eighties we only had 'Modelarnia' roughly translated to 'Model building workshop' - a woodworking and electronics shop for kids to built RC models
https://kok.kepno.pl/modelarnia-2/ https://www.mdkstalowawola.pl/2018/09/05/miej … -organizacyjne/
and HAM (amateur radio enthusiast) clubs. My primary school still had woodworking workshop up to around 1992. One year we were whittling wood for final grade, I remember making an ergonomic shaped base for a homemade joypad 😀, the next wood shop was gone and we were learning Turbo Pascal on really crappy ATs with small HDDs and EGA monitors.

there are also those events in Baltimore/Pennsylvania/New Jersey https://vcfed.org/repair-workshops/

I got the post card, plugged it in and this is all it displays.
[ -- --, -12V, +12V, +5V, CLK ]
I'm not sure if my card is faulty or not, but it seems to do the exact same thing when powering up with the CPU removed.
Before I go and rush-order more parts though, I thought I'd come back here. Does anyone with a POST card know what this means?

alexparr wrote on 2024-01-30, 22:14:

I got the post card, plugged it in and this is all it displays. [ -- --, -12V, +12V, +5V, CLK ] I'm not sure if my card is fault […]
Show full quote

I got the post card, plugged it in and this is all it displays.
[ -- --, -12V, +12V, +5V, CLK ]
I'm not sure if my card is faulty or not, but it seems to do the exact same thing when powering up with the CPU removed.
Before I go and rush-order more parts though, I thought I'd come back here. Does anyone with a POST card know what this means?

That means the motherboard is not POSTing. Which typically suggests a significant problem. It's not clear on whether it's the motherboard or CPU.

This is where having multiple components can come in handy to swap parts around and narrow things down to one component.

alexparr wrote on 2024-01-30, 22:14:

I got the post card, plugged it in and this is all it displays. [ -- --, -12V, +12V, +5V, CLK ] I'm not sure if my card is fault […]
Show full quote

I got the post card, plugged it in and this is all it displays.
[ -- --, -12V, +12V, +5V, CLK ]
I'm not sure if my card is faulty or not, but it seems to do the exact same thing when powering up with the CPU removed.
Before I go and rush-order more parts though, I thought I'd come back here. Does anyone with a POST card know what this means?

That's bad news I guess. If there were no post codes displayed that means the BIOS don't even start to do anything. Reason might be broken CPU, wrong jumper settings for CPU or dead BIOS as an example. The LEDs indicating the supply voltages are present and there's no short/reset. (Idk why there's no 3.3V supply on the PCI bus but maybe thats normal for early pci on 486?)

alexparr wrote on 2024-01-30, 22:14:

I got the post card, plugged it in and this is all it displays. [ -- --, -12V, +12V, +5V, CLK ] I'm not sure if my card is fault […]
Show full quote

I got the post card, plugged it in and this is all it displays.
[ -- --, -12V, +12V, +5V, CLK ]
I'm not sure if my card is faulty or not, but it seems to do the exact same thing when powering up with the CPU removed.
Before I go and rush-order more parts though, I thought I'd come back here. Does anyone with a POST card know what this means?

Does the cpu get warm when you start the board? You can "measure" it with your fingers. For this short test it's good to not put a heatsink on the cpu.
If its getting warm / hot (after lets say 10 seconds), then at least power is provided to the cpu.
Did you always run the DX2-66 without a heatsink? Just asking because I did not see one on those pictures.

EDIT: I overlooked that you already wrote that the cpu gets hot, sorry.
OK, maybe try underclocking it, so set the bus to the lowest value, like 25MHz.

Shponglefan wrote on 2024-01-30, 22:25:

That means the motherboard is not POSTing. Which typically suggests a significant problem. It's not clear on whether it's the motherboard or CPU.

This is where having multiple components can come in handy to swap parts around and narrow things down to one component.

Before I posted about it, I tried it with and without all of the expansion cards I had plugged in, as the manual suggested. Same result.

pc-sound-legacy wrote on 2024-01-30, 22:30:

Reason might be broken CPU, wrong jumper settings for CPU or dead BIOS as an example.

I never messed with the jumper settings, so it can't be that.

CoffeeOne wrote on 2024-01-30, 22:48:

Does the cpu get warm when you start the board? You can "measure" it with your fingers. For this short test it's good to not put a heatsink on the cpu.
If its getting warm / hot (after lets say 10 seconds), then at least power is provided to the cpu.
Did you always run the DX2-66 without a heatsink? Just asking because I did not see one on those pictures.

As I stated in the original post, it gets about as hot as it did before the system died. It didn't come with a heatsink when I ordered the motherboard—yes, the motherboard came with the CPU pre-equipped, with the jumpers already set to their correct values for said CPU.

Shponglefan wrote on 2024-01-30, 22:25:

That means the motherboard is not POSTing. Which typically suggests a significant problem. It's not clear on whether it's the motherboard or CPU.

This is where having multiple components can come in handy to swap parts around and narrow things down to one component.

Before I posted about it, I tried it with and without all of the expansion cards I had plugged in, as the manual suggested. Same result.

pc-sound-legacy wrote on 2024-01-30, 22:30:

Reason might be broken CPU, wrong jumper settings for CPU or dead BIOS as an example.

I never messed with the jumper settings, so it can't be that. It would kinda suck if the BIOS died on me, as that's another thing that can't be easily replaced—at least in my case.

CoffeeOne wrote on 2024-01-30, 22:48:

...Did you always run the DX2-66 without a heatsink? Just asking because I did not see one on those pictures.

It didn't come with a heatsink when I ordered the motherboard—yes, the motherboard came with the CPU pre-equipped, with the jumpers already set to their correct values for said CPU.

CoffeeOne wrote on 2024-01-30, 22:48:

OK, maybe try underclocking it, so set the bus to the lowest value, like 25MHz.

I don't know what jumpers do what. There is no documentation about this motherboard, so I'm kind of just stuck at 66MHz—unless of course I want to break something else.

Remove any cards or peripherals that you don't need (sound, drive controllers etc), pare it down to just PSU/MB/CPU/RAM/Video.
Reseat everything, including ram, cpu etc.
Check all jumper settings.
Start there.

alexparr wrote on 2024-01-30, 22:56:

.....
I don't know what jumpers do what. There is no documentation about this motherboard, so I'm kind of just stuck at 66MHz—unless of course I want to break something else.

The setting is actually printed on the mainboard, the setting for 25MHz, 33MHz and 40MHz is documented.
So set it to 25MHz and check what happens.

EDIT: There are 2(!) sections with the writing: 25, 33, 40 MHz. But I cannot read that clearly from these pictures

MORE EDIT: If I were you, I would get another cpu. Running a DX2-66 without any heatsink for a longer period of time might have killed it.

CoffeeOne wrote on 2024-01-30, 23:03:

The setting is actually printed on the mainboard, the setting for 25MHz, 33MHz and 40MHz is documented. So set it to 25MHz and c […]
Show full quote

alexparr wrote on 2024-01-30, 22:56:

.....
I don't know what jumpers do what. There is no documentation about this motherboard, so I'm kind of just stuck at 66MHz—unless of course I want to break something else.

The setting is actually printed on the mainboard, the setting for 25MHz, 33MHz and 40MHz is documented.
So set it to 25MHz and check what happens.

EDIT: There are 2(!) sections with the writing: 25, 33, 40 MHz. But I cannot read that clearly from these pictures

The ones on the left seem to be for the PCI bus. The ones in the middle are un-labeled. Remind me though, what does "OP" and "CL" mean?
Also for some reason JP13 doesn't have any jumper pins connected.