Is this one of the VIA chipsets that work with just one RAM stick? Have you tried two sticks?

Besides that the jumpering of this mainboard is quite tricky, have you doublechecked _everything_?

JonF wrote on 2023-01-15, 08:15:

486-VIP-IO […]
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486-VIP-IO

I pulled this motherboard out of my storage bin recently and it’s not working. I’ve done some troubleshooting but no luck yet.

-486 DX2 50mhz, 16mb FPM RAM stick
-No video, no beeps
-ISA slot check card shows 4 dashes for error codes. Voltages on ISA bus are OK. Clock flashes intermittently. IRDY flashes once shortly after power up then nothing. Frame stays light. Reset LED is off unless I short reset button pins then it lights.
-CPU, RAM, video card tested in other machines.
-Tried other Ram, cpu, video combos and still nothing.(updated jumpers for cpu)
-CPU VCC pins are 5V, clock pin seems to get a signal.
However CPU reset pin is stuck high-I think this isn’t normal?

I tried erasing and reflashing the Award BIOS EPROM with a matching .bin file online but that didn’t change anything.

Any ideas or troubleshooting guidance? Attached picture of board test setup.

Don't try to run something like shown in the picture!
A mainboard located on ESD packing stuff, nooooooooo. The packing should be electrically conductive. You know what that means, don't you?

CoffeeOne wrote on 2023-01-15, 12:06:

JonF wrote on 2023-01-15, 08:15:

486-VIP-IO […]
Show full quote

486-VIP-IO

I pulled this motherboard out of my storage bin recently and it’s not working. I’ve done some troubleshooting but no luck yet.

-486 DX2 50mhz, 16mb FPM RAM stick
-No video, no beeps
-ISA slot check card shows 4 dashes for error codes. Voltages on ISA bus are OK. Clock flashes intermittently. IRDY flashes once shortly after power up then nothing. Frame stays light. Reset LED is off unless I short reset button pins then it lights.
-CPU, RAM, video card tested in other machines.
-Tried other Ram, cpu, video combos and still nothing.(updated jumpers for cpu)
-CPU VCC pins are 5V, clock pin seems to get a signal.
However CPU reset pin is stuck high-I think this isn’t normal?

I tried erasing and reflashing the Award BIOS EPROM with a matching .bin file online but that didn’t change anything.

Any ideas or troubleshooting guidance? Attached picture of board test setup.

Don't try to run something like shown in the picture!
A mainboard located on ESD packing stuff, nooooooooo. The packing should be electrically conductive. You know what that means, don't you?

ESD foil is just conductive enough not to create static charges and possibly to dissipate them. Really their resistance is pretty high. (1000s of Ohms)
I can't think of any risk running hardware on top of it like the OP does.

was it working before you stored it away?

Doornkaat wrote on 2023-01-15, 12:20:

CoffeeOne wrote on 2023-01-15, 12:06:

JonF wrote on 2023-01-15, 08:15:

486-VIP-IO […]
Show full quote

486-VIP-IO

I pulled this motherboard out of my storage bin recently and it’s not working. I’ve done some troubleshooting but no luck yet.

-486 DX2 50mhz, 16mb FPM RAM stick
-No video, no beeps
-ISA slot check card shows 4 dashes for error codes. Voltages on ISA bus are OK. Clock flashes intermittently. IRDY flashes once shortly after power up then nothing. Frame stays light. Reset LED is off unless I short reset button pins then it lights.
-CPU, RAM, video card tested in other machines.
-Tried other Ram, cpu, video combos and still nothing.(updated jumpers for cpu)
-CPU VCC pins are 5V, clock pin seems to get a signal.
However CPU reset pin is stuck high-I think this isn’t normal?

I tried erasing and reflashing the Award BIOS EPROM with a matching .bin file online but that didn’t change anything.

Any ideas or troubleshooting guidance? Attached picture of board test setup.

Don't try to run something like shown in the picture!
A mainboard located on ESD packing stuff, nooooooooo. The packing should be electrically conductive. You know what that means, don't you?

ESD foil is just conductive enough not to create static charges and possibly to dissipate them. Really their resistance is pretty high. (1000s of Ohms)
I can't think of any risk running hardware on top of it like the OP does.

I believe you are mostly right. But still, what's the point in doing it?
Better is to use a wooden plate or copy paper.
I once managed to produce some smoke when I ran a mainboard on a ESD bag (maybe that one was more conductive than usual). I will never do it again.

CoffeeOne wrote on 2023-01-15, 14:50:

I believe you are mostly right. But still, what's the point in doing it?
Better is to use a wooden plate or copy paper.
I once managed to produce some smoke when I ran a mainboard on a ESD bag (maybe that one was more conductive than usual). I will never do it again.

I use a plain cardboard box, like what a motherboard typically comes in for all my bench testing.

However CPU reset pin is stuck high-I think this isn’t normal?

No that is not normal, on your Diag card reset led should flash once at power on....does it ?

JonF wrote on 2023-01-15, 08:15:

Any ideas or troubleshooting guidance? Attached picture of board test setup.

Connect reset switch, see if pressing it changes the state of CPU reset. And the ISA reset signal as well, which should be visible on the POST card LED.
Also, from experience, some 486 mobos can be super picky about RAM sticks. Try all sticks you have and try first and last slot each time.

Deunan wrote on 2023-01-15, 18:25:

JonF wrote on 2023-01-15, 08:15:

Any ideas or troubleshooting guidance? Attached picture of board test setup.

Connect reset switch, see if pressing it changes the state of CPU reset. And the ISA reset signal as well, which should be visible on the POST card LED.
Also, from experience, some 486 mobos can be super picky about RAM sticks. Try all sticks you have and try first and last slot each time.

Yea I was gonna say also, there's a 16 mb 72 pin FPM simm in there. Maybe the board doesnt like a single stick of that capacity for whatever reason.

I’ve removed the ESD bag from underneath just for better practice going forward. The bag itself measures open circuit on my multimeter so I doubt it caused any harm.

I’ve tried 2 Ram sticks as well, but according to the manual I think one should be fine too. I’ll have to try more combos as well.

The reset LED lights as I press the power button turning it on, then stays off.

The reset SW lights the reset LED on the ISA bus.
For the CPU, I must have measured incorrectly last night. RESET is not stuck high. RESET pin is low, then goes high and back to low when reset SW is pressed. SRESET pin on CPU stays low.

I really don’t remember if this board was working or not before storage unfortunately. I think I got it in a lot from a flea market or something awhile back.

Some more clues:

-I plugged in a keyboard and no lights turn on or flash ever.
-I tried a bunch of other RAM I have around and no change to behavior.
-I tried swapping BIOS from a working 486 M919 MB I have. No change on the VIP. The M919 doesn’t post with the VIP BIOS but it does at least give error codes and shows at least some life signs.

JonF wrote on 2023-01-15, 20:59:

Some more clues: […]
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Some more clues:

-I plugged in a keyboard and no lights turn on or flash ever.
-I tried a bunch of other RAM I have around and no change to behavior.
-I tried swapping BIOS from a working 486 M919 MB I have. No change on the VIP. The M919 doesn’t post with the VIP BIOS but it does at least give error codes and shows at least some life signs.

Probably a silly question, but just to make sure: 😁

Did you set the clock to 25MHz?

I do have the CPU clock set to 50mhz. Just tried setting to 25mhz and still nothing though.

JonF wrote on 2023-01-15, 21:11:

I do have the CPU clock set to 50mhz. Just tried setting to 25mhz and still nothing though.

Oh no.
DX2 means internal double clock rate, so DX2-50 needs 25MHz. If you are lucky it will boot at 33MHz, too, but there will be no signs of life at 40 or 50MHz.
Are you sure that the CPU still works?

EDIT: You ran the DX2-50 at 100MHz without a cooler. Maybe it is really dead now. Unlikely but still possible 🙁
But the way a cooler would not hurt anyway ....

I just tested the CPU in another machine it’s working fine.

The CPU stays cold no matter how long I leave this motherboard on so I don’t think it is really even starting properly.

Yea hard to say. Could be a problem with the board such as a bad trace or possibly lifted legs etc. on some of the chips. May be time to break out the microscope / multimeter and start probing...

JonF wrote on 2023-01-15, 21:59:

I just tested the CPU in another machine it’s working fine.

The CPU stays cold no matter how long I leave this motherboard on so I don’t think it is really even starting properly.

Yes, so it behaves like you have no CPU inserted. Not very good.
Maybe the socket 3 is broken?
You already mearsured the vcc pins of the socket, you wrote before.
Can you do it when the CPU is in? You can remove all cards for this kind of test ...

By the way DX2-50MHz is a great CPU to test 486-boards: It is 5 volts, intel, and operates at low clock 25MHz.

What you can also do before the voltage test (just to be on the safe side): Remove your cache sram chips (just in cases some traces are broken and something is shorted). You now have only 128kB anyway, so only 5 chips to remove 😉

Some progress, I found a fuse near the power connector that had kohm level resistance. I jumpered in a new fuse and now the keyboard gets 5V. Now, 2 of the keyboard lights light as normal for 1 second, then all 3 flash and turn off. No error code or video.

I did measure the 5V from the bottom side with the CPU inserted.

Also, my jumpers are set for 256kb cache. 4 chips + 1 tag is a config in the manual. I tried looking up these SRAM chips online but there is no info on what size they are.

JonF wrote on 2023-01-15, 22:48:

I did measure the 5V from the bottom side with the CPU inserted.

Do you have a scope? If so, probe BIOS ROM /CE and /OE pins for activity after reset (one of those might be shorted to GND permanently, check that first). This way you'll know if the CPU exits self-test after reset and tries to fetch code. Well, assuming the mobo chipset isn't totaly toast, but then again if there is no activity you can check on the CPU data/address lines directly (at the socket).

Try the Diag card in a PCI slot or two, have had some PCI boards that will not output codes to ISA slots but do to PCI slots