Unfortunatly I have not got any speakers (you know pc speakers)
near the CPU socket, only from the bottom.

You're using a 3V CPU and have jumpered it for 3V, that means that the VRM on the board (primarily that MOSFET just to the left of the CPU socket) is regulating the voltage down from 5V to 3V, which with a primitive linear design like this generates a lot of heat. If it's the rear of the MOSFET, then that's pretty normal.

You might need a power supply like this one with a power switch.
https://www.ebay.com/itm/Athena-Power-AP-AT30 … 5gAAMXQ01tRTOc-

Or maybe just the right ATX to AT PSU adapter with switch.
https://www.ebay.com/itm/Athena-Power-Cable-A … 74e9a92bdfd5a7c

All right, so I was on a garage sale and I picked up a new motherboard. It was cheap (7$). Guess what, it booted right up (after setting the jumpers of course)
Thanks to everyone that helped me.
windowsio

Intel486dx33 wrote:

You might need a power supply like this one with a power switch. https://www.ebay.com/itm/Athena-Power-AP-AT30 … 5gAAMXQ01tRTOc- […]
Show full quote

You might need a power supply like this one with a power switch.
https://www.ebay.com/itm/Athena-Power-AP-AT30 … 5gAAMXQ01tRTOc-

Or maybe just the right ATX to AT PSU adapter with switch.
https://www.ebay.com/itm/Athena-Power-Cable-A … 74e9a92bdfd5a7c

yes, I had that adapter

If the chipset gets very hot as in HOT it's usually done for.
Good you purchased a new one.

Greetings all.

I have acquired the same motherboard and have same problem.

Manual found at:

http://www.win3x.org/uh19/motherboards/2495
or
https://stason.org/TULARC/pc/motherboards/F/F … ON-486-419.html

does not list Am486DX4-120, but the board came with it.

Jumpers seems to be set correctly, but I would need second opinion to verify this please. As of now I cannot get a video, however it doesn't seem to be completely dead.
The processor warms up quickly when powered on, keyboard LEDs blink on when it powers on. I did get some beeps but was unable to identify the code, chipset is cool to touch and there are no obvious mechanical damages visible. I installed brand new battery, cooler, and memory but it was a "no go".
I tried Cirrus Logic VLB video card (which I don't know if it was good), and regular ISA graphics but still no luck. There are many other jumpers on that board unlisted in the manual as well as network resistors for different CPUs, but I'm reluctant to touch those without guidance.
What would be the absolute minimum to check if this board is still alive? Would it start with no CPU or RAM?
I could swap Intel 486DX2-50 (SX641) to see if maybe CPU is here to blame or IBM blue lightning 496DX2-66 (486-V266GA), but would need help setting up correct jumpers.
Any suggestions to revive this motherboard highly appreciated.

Edit: When no memory is installed I get 3 short beeps, short break and then 3 beeps keep repeat ... voltage regulator is warm (bot not hot) to touch and CPU radiator is warm to touch.

Deksor wrote on 2019-03-23, 14:31:

Where does the board get hot ? On the opti chips ? Maybe something is shorted ? Check on the AT slot if the GND isn't shorted with +5v/+12v

How would I do that?

the psu cables when connected to motherboard incorrect socket order so be sure they are correct and i recommend a heatsink for that cpu is why it has that blemish on it could be dead from teatstroke 🤣

I'd wanna check the orientation of the resistor pack, it may or may not matter depending on type of resistor pack, if it's all resistors to one pin then it matters, just resistors one pin to another, then not.

zapbuzz wrote on 2021-09-16, 18:13:

the psu cables when connected to motherboard incorrect socket order so be sure they are correct and i recommend a heatsink for that cpu is why it has that blemish on it could be dead from teatstroke 🤣

What's that, this board doesn't have standard "blacks to the middle" PSU socket layout?

Yes, while a cold 5x86 should boot to point of trying to load OS without a heatsink, if it's never had a heatsink it could be dead, also if you've got it in there powered and warming up while settings are checked it may get too warm to function when you get a setting that should boot.

I have a similar, only older board (5V CPU only). There's a silly trick question: JP23/22/21 do not follow each other as printed in config table on the board, but are swapped JP23/21/22. As I can see in the photo, you have the jumpers set to FSB 50 MHz, but the DX4-120 is supposed to be 40 MHz. Toss the JP21/22 links correctly and see if you can move on.

zapbuzz wrote on 2021-09-16, 18:13:

the psu cables when connected to motherboard incorrect socket order so be sure they are correct and i recommend a heatsink for that cpu is why it has that blemish on it could be dead from teatstroke 🤣

Cables powering the board are "black inside", heatsink is there while the board is powered on and the blemish is from thermal paste... so, check, check and check.

BitWrangler wrote on 2021-09-16, 18:14:

I'd wanna check the orientation of the resistor pack, it may or may not matter depending on type of resistor pack.

Yeah, resistor pack... I'm clueless about those and their orientation. Not mentioned in the "manual" or on anywhere on the board itself.

BitWrangler wrote on 2021-09-16, 18:14:

... if it's all resistors to one pin then it matters, just resistors one pin to another, then not.

This I don't understand. Resistor pack has visible pin one mark, but since this is undocumented I don't know if their position is correct.

Ydee wrote on 2021-09-17, 10:53:

I have a similar, only older board (5V CPU only). There's a silly trick question: JP23/22/21 do not follow each other as printed in config table on the board, but are swapped JP23/21/22. As I can see in the photo, you have the jumpers set to FSB 50 MHz, but the DX4-120 is supposed to be 40 MHz. Toss the JP21/22 links correctly and see if you can move on.

I noticed this. JP 21/22/23 is in wrong order... ? This is VERY confusing. Did you experiment with your jumpers or went with the "manual"? Is the silkscreen correct?
In my case the board came with Am486DX4-120... and what you is original setting, but I tried to switch to i486DX2-50 (5V) and still no go. There are many other undocumented jumpers on this board like J69, J70, J74 etc. Is there a jumper to reset CMOS settings? One of these two next to BIOS chip ?(J60 and J69 i think)
What CPU do you have on your board?
I purchased i486DX4-100 (actually I think it works as 33MHz x 3) and waiting for it to be delivered. With this CPU there should me less confusion setting it up, since there are actually specific settings for it in the manual, as oppose to Am486DX4-120.
Meanwhile I think my EVGA 500W PSU seems to have gone bad. I was wondering if incorrect jumper setting might have damaged it? Until I RMA the PSU, I cannot proceed.
Anyway, if (I assume) your board works fine, you might be my closest ally to make this board boot again.

mat919 wrote on 2021-09-17, 12:12:

This I don't understand. Resistor pack has visible pin one mark, but since this is undocumented I don't know if their position is correct.

Pin 1 is the box or square on those headers, printed under them on the board, so in the picture if the pin one mark is to the left that should be correct.

BitWrangler wrote on 2021-09-17, 12:39:

mat919 wrote on 2021-09-17, 12:12:

This I don't understand. Resistor pack has visible pin one mark, but since this is undocumented I don't know if their position is correct.

Pin 1 is the box or square on those headers, printed under them on the board, so in the picture if the pin one mark is to the left that should be correct.

This is how it configured right now. Does this look like correct? Because it looks opposite to what you've said.

Yeah just to be sure, I'd flip the spot on the AMD-INTEL row around, and put the spot where the X is to select DX. Although with that extra box there under JP-A you wonder whether it'd supposed to flip again for SX setting.... oh wouldn't it be nice to find original manual.. or original engineer to give him an ear full.

I think the 'B' type resistor networks are in pairs (so 1&2, 3&4, 5&6, 7&8), and the '0' means zero ohms. So I think those blocks are effectively just jumpers. I'd guess from the silkscreen that JPB and JPC select between Intel (pins 3-10 of JPB), AMD (pins 1-8 of JPB) and Cyrix (pins 3-10, the only ones with header pins, of JPC). The move JPA to set the 486 type. But I don't know which settings would be right for an Am486DX4.

Have you got a multimeter you can use to check what voltage is going to the CPU?

mat919 wrote on 2021-09-17, 12:29:

I noticed this. JP 21/22/23 is in wrong order... ? This is VERY confusing. Did you experiment with your jumpers or went with the […]
Show full quote

I noticed this. JP 21/22/23 is in wrong order... ? This is VERY confusing. Did you experiment with your jumpers or went with the "manual"? Is the silkscreen correct?
In my case the board came with Am486DX4-120... and what you is original setting, but I tried to switch to i486DX2-50 (5V) and still no go. There are many other undocumented jumpers on this board like J69, J70, J74 etc. Is there a jumper to reset CMOS settings? One of these two next to BIOS chip ?(J60 and J69 i think)
What CPU do you have on your board?
I purchased i486DX4-100 (actually I think it works as 33MHz x 3) and waiting for it to be delivered. With this CPU there should me less confusion setting it up, since there are actually specific settings for it in the manual, as oppose to Am486DX4-120.
Meanwhile I think my EVGA 500W PSU seems to have gone bad. I was wondering if incorrect jumper setting might have damaged it? Until I RMA the PSU, I cannot proceed.
Anyway, if (I assume) your board works fine, you might be my closest ally to make this board boot again.

I'm afraid I can't help you with advice, my board is an older version of HOT 419 with the same chipset, but with a slightly modified configuration. But the configuration for the FSB is the same, and I noticed it's set to 50 MHz on your photo, which is why I wrote to you. The jumper settings table is correct, but the jumper numbers are jumbled, so it can lead to a mistake if a person is inattentive. For AM486DX4-120, the FSB should be set to 40 MHz (yellow indicated in my photo above).

I cleared the CMOS by removing the connection on the jumper for the external battery (my board had a onboard NiCD battery), you can just take out CR2032. J69 is for setting up CPU RDY# Delay, J71 and others to set memory mode for support 1 or 2 VESA master mode local bus. I enclose a manual by which I have successfully configured my board, that's where you learn more about it.

I have the Am486DX2-66 CPU because my model does not have a voltage regulator and only supports 5V, as I wrote.

Edit: I think you can erase the CMOS by removing the link from the J1 jumper above the DIN keyboard connector - so I had it with me.