Is there a polyfuse for the keyboard? Sometimes they go bad and trip at lower than spec currents.

Matrolisk wrote on 2024-03-17, 21:14:

Shortly after booting up the computer and entering the BIOS the keyboard stops working. It's an American Megatrends BIOS that h […]
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Shortly after booting up the computer and entering the BIOS the keyboard stops working.
It's an American Megatrends BIOS that has mouse support.

There does not appear to be any damage to the motherboard, no burn marks or loose connections.

I've tried different keyboards with no change.

Any help would be appreciated.

M-Tech (MTI)/Rise R418 PCI-486 Rev 1
AMD 5x86
AMD Mach 64
Sound Blaster 16

The computer maybe is just crashing after a while. But one minute is quite a long time, so I would guess that the CPU is overheating.

kingcake wrote on 2024-03-17, 21:21:

Is there a polyfuse for the keyboard? Sometimes they go bad and trip at lower than spec currents.

There are four yellow fuses next to where the keyboard plugs in. How would I go about identifying which one is related to the keyboard.
https://imgbb.com/r65QQZB - Bottom Left

CoffeeOne wrote on 2024-03-17, 21:24:

The computer maybe is just crashing after a while. But one minute is quite a long time, so I would guess that the CPU is overheating.

I have a heatsink on it, and I applied thermal paste to it just like on a modern cpu.
What would be a good way to find out the cpus temp.

Matrolisk wrote on 2024-03-17, 21:14:

Shortly after booting up the computer and entering the BIOS the keyboard stops working. It's an American Megatrends BIOS that h […]
Show full quote

Shortly after booting up the computer and entering the BIOS the keyboard stops working.
It's an American Megatrends BIOS that has mouse support.

There does not appear to be any damage to the motherboard, no burn marks or loose connections.

I've tried different keyboards with no change.

Any help would be appreciated.

M-Tech (MTI)/Rise R418 PCI-486 Rev 1
AMD 5x86
AMD Mach 64
Sound Blaster 16

OK, so what happens when you don't enter the Bios? Can you boot from floppy?

Have you tried other keyboards?

As for the "might be crashing", is it just the keyboard that stops working while the mouse keeps on chugging?

Here's another, much better photo of that board. You sure those yellow components are fuses? They look like caps to me. If they are this is the best-fused board ever - they're used all over the place. I don't see anything else that might be a fuse around that area either.

>I have a heatsink on it
>AMD 5x86

heatsink and a fan, right?

>They look like caps to me
they sure are tantalum caps, there are no keyboard fuses visible on this board, just three inductors L1 L2 and one above the keyboard connector I dont see the designation, those look beefy AF and I doubt they are the problem 😀

So after some more testing I was able to determine that it only happens in the bios.
The computer seems to be fine if I don't enter the bios.

I plugged in a mouse and it stops working to, so not just a keyboard issue.

Is there way to fix this? Can I replace the bios chip?

Matrolisk wrote on 2024-03-19, 22:48:

..... The computer seems to be fine if I don't enter the bios. […]
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.....
The computer seems to be fine if I don't enter the bios.

I plugged in a mouse and it stops working to, so not just a keyboard issue.
.....

What exactly is working? I mean what do you run?
Which OSs? DOS? Windows 3.1? Windows 95? Which programs can you run?

I'm just running dos and some games and such off of disks.

All that seems to be crashing is the bios setup utility whenever I try to use it.

Matrolisk wrote on 2024-03-20, 22:14:

I'm just running dos and some games and such off of disks.

All that seems to be crashing is the bios setup utility whenever I try to use it.

Fine.
DOS alone is a not a good stabilty test. But when you run Doom for more than 5 minutes, it counts as a stability test in my opinion.

Also in your first message you list some things, but miss the most important: The RAM!
You could test with the 30pin modules only. That avoids problems coming from EDO RAM. You know that you should not use EDO RAM, don't you?

Still I cannot believe that the computer works without any problems in DOS, but hard crashes when being in the Bios. In Bios normally all timing parameter values are set to really safe (=slow) values.

I removed the EDO Ram with no change in the bios issue.

I did however discover that the more that is plugged in that faster the bios crashes.
When I had a floppy, mouse and the keyboard plugged in the bios setup would not even load.

On a side note I'm currently using an old small harddrive and would like to be able to use an sd card. Both for the reliability and the capacity.
However when I plug in the adaptor only the power led comes on. The sd card is formatted to FAT16 2GB. I did notice that the onboard ide connector which I'm using is a 40wire version while the adapter wants 80.
Can I use the onboard connecter or do I need a ide card which supports 80wire connector and if so what should I look for.

More stuff plugged in = quicker crash? Hmm... maybe time to try a different PSU, just to rule that out too.

The PSU is a Corsair CX450M that's connected to an adaptor to convert the 20pin to the at connector that old motherboards used.

I've seen RTC/CMOS issues cause weirdness in the BIOS setup menu. Like freezing or long delays for input presses.
In DOS can you set and read the time and date w/o the system freezing? Does it keep time in DOS once you set it?

If me would swap out the video for a Oak or Trident ISA or S3 Trio PCI and pull the SB card, just to see what happens.
Next would add a serial ISA card and try the mouse there (with onboard disabled). ... sorry if you all ready tried these but see no ref you altered/tried anything else...

kingcake wrote on 2024-03-25, 00:45:

I've seen RTC/CMOS issues cause weirdness in the BIOS setup menu. Like freezing or long delays for input presses.
In DOS can you set and read the time and date w/o the system freezing? Does it keep time in DOS once you set it?

I was able to check and change the time. After restarting the computer the clock stayed at the new time.

Horun wrote on 2024-03-25, 03:25:

If me would swap out the video for a Oak or Trident ISA or S3 Trio PCI and pull the SB card, just to see what happens.
Next would add a serial ISA card and try the mouse there (with onboard disabled). ... sorry if you all ready tried these but see no ref you altered/tried anything else...

I have pulled the SB card and have kept it out during all this testing.

I tried an ISA gpu card and the computer crashed before loading the bios setup.
Plugged in an ISA serial/parallel card with mouse plugged in and it crashed almost immediately after loading into the bios setup.

For reference, during most of my testing there has only been cpu/fan, gpu and the keyboard. No mouse or hard drive.

Matrolisk wrote on 2024-03-25, 22:16:

I was able to check and change the time. After restarting the computer the clock stayed at the new time. […]
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kingcake wrote on 2024-03-25, 00:45:

I've seen RTC/CMOS issues cause weirdness in the BIOS setup menu. Like freezing or long delays for input presses.
In DOS can you set and read the time and date w/o the system freezing? Does it keep time in DOS once you set it?

I was able to check and change the time. After restarting the computer the clock stayed at the new time.

Horun wrote on 2024-03-25, 03:25:

If me would swap out the video for a Oak or Trident ISA or S3 Trio PCI and pull the SB card, just to see what happens.
Next would add a serial ISA card and try the mouse there (with onboard disabled). ... sorry if you all ready tried these but see no ref you altered/tried anything else...

I have pulled the SB card and have kept it out during all this testing.

I tried an ISA gpu card and the computer crashed before loading the bios setup.
Plugged in an ISA serial/parallel card with mouse plugged in and it crashed almost immediately after loading into the bios setup.

For reference, during most of my testing there has only been cpu/fan, gpu and the keyboard. No mouse or hard drive.

What RAM are you using? Pictures?

https://imgur.com/a/79gHNxl
The chips say - nec japan - 424400-70 9115FUO29

Matrolisk wrote on 2024-03-25, 22:16:

I have pulled the SB card and have kept it out during all this testing. […]
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Horun wrote on 2024-03-25, 03:25:

If me would swap out the video for a Oak or Trident ISA or S3 Trio PCI and pull the SB card, just to see what happens.
Next would add a serial ISA card and try the mouse there (with onboard disabled). ... sorry if you all ready tried these but see no ref you altered/tried anything else...

I have pulled the SB card and have kept it out during all this testing.

I tried an ISA gpu card and the computer crashed before loading the bios setup.
Plugged in an ISA serial/parallel card with mouse plugged in and it crashed almost immediately after loading into the bios setup.

For reference, during most of my testing there has only been cpu/fan, gpu and the keyboard. No mouse or hard drive.

What ? An ISA video card on a 486 caused it to crash ? What exact ISA video card ?
Sounds like the board has some major issues because an ISA in a 486 should never cause a crash....
Also: what PSU are you using ? sounds like you are not loading the PSU enough (with just board, 486 cpu and video).
Most PSU require minimum of a few amps on the +5 and +12 to be stable.....hook up a few HD's just to molex to draw more