borja wrote on 2024-05-21, 16:09:

I removed all cards and connected an ISA debug card and all LEDs light up except RST led as it shoud.

Reset LED should light up briefly and then go away. You should hook up a manual reset button and make sure it changes the LED state. 03 is pretty low code (and no beeps) so the BIOS didn't get very far - I'd start poking around RTC/CMOS (try the clear jumper) and KBC (keyboard controller). Some BIOSes can't deal with invalid CMOS data so make sure you have some battery hooked up so that clearing it will actually work.

If you can dump the BIOS image (or find something very close online) someone could disassemble it and ideally narrow down what happens between 03 and 04

Deunan wrote on 2024-05-21, 22:00:

borja wrote on 2024-05-21, 16:09:

I removed all cards and connected an ISA debug card and all LEDs light up except RST led as it shoud.

Reset LED should light up briefly and then go away. You should hook up a manual reset button and make sure it changes the LED state. 03 is pretty low code (and no beeps) so the BIOS didn't get very far - I'd start poking around RTC/CMOS (try the clear jumper) and KBC (keyboard controller). Some BIOSes can't deal with invalid CMOS data so make sure you have some battery hooked up so that clearing it will actually work.

Yes, RST LED changes state when press the button. LEDs seems to be fine.

I will try with the coin battery next days. Maybe is the issue, but should not be differences using the power supply.

jakethompson1 wrote on 2024-05-21, 23:33:

If you can dump the BIOS image (or find something very close online) someone could disassemble it and ideally narrow down what happens between 03 and 04

I only have a CH341 reader, never tried to dump such an old BIOS. I will do a bit of research looking for what device i need.

Well if you are looking to buy a new EPROM programmer then XGecu T48 is something you should consider.

jakethompson1 wrote on 2024-05-21, 23:33:

If you can dump the BIOS image (or find something very close online) someone could disassemble it and ideally narrow down what happens between 03 and 04

Hi!

I couldn't find documentation for this motherboard, so i dont know where the clear cmos jumper is. This is a picture of the board, it has an M symbol, i can't find a model number. Do you recognize the brand logo?

I aready checked to power on with the battery attached and it gave me same error code 03.

Thanks

I think the manufacturer is MITAC. But the most similar motherboard i was able to find is the compumate sa-286.

borja wrote on 2024-05-23, 16:39:

I think the manufacturer is MITAC

I see SUNTAC chipset there. There's quite a few of these mobos out there, and Predator99 even started a nice BIOS collection: 80286 BIOS image collection
Try some other BIOS, like AMI, maybe the codes will tell you more. Some of these BIOSes are rather limited in terms of HDD support and options in general but there's plenty to choose from.

I've only dealt with a few of these but the PCB quality is so-so, perhaps due to age of these systems, it's big and tends to flex - this causes some trace and via cracking. Annoying as hell to find and fix. Pretty much impossible without a scope and some BIOS hacking, unless someone has a nice logic analyzer.

Deunan wrote on 2024-05-23, 16:53:

I see SUNTAC chipset there. There's quite a few of these mobos out there, and Predator99 even started a nice BIOS collection: 80 […]
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borja wrote on 2024-05-23, 16:39:

I think the manufacturer is MITAC

I see SUNTAC chipset there. There's quite a few of these mobos out there, and Predator99 even started a nice BIOS collection: 80286 BIOS image collection
Try some other BIOS, like AMI, maybe the codes will tell you more. Some of these BIOSes are rather limited in terms of HDD support and options in general but there's plenty to choose from.

I've only dealt with a few of these but the PCB quality is so-so, perhaps due to age of these systems, it's big and tends to flex - this causes some trace and via cracking. Annoying as hell to find and fix. Pretty much impossible without a scope and some BIOS hacking, unless someone has a nice logic analyzer.

Thank you for the link. Thanks to it i have found the exact model number of the board ST62M02-B.

I would look into how i can change the BIOS, can i flash it to the EEPROM or i need other model?

You'll need some EPROM programmer, or access to one. Then you'll need a blank chip for the file you'll download to try out. Since you might be trying it a few times I would suggest you buy an "EPROM emulator chip" - that is in fact a Flash chip but pin-compatible with standard EPROM. And since it's a Flash it can be erased electrically, by the programmer, no need for UV lamp. For example W27E512 or SST27SF512. That being said if you can erase standard EPROMS with UV then you can pick such a chip as well.

If you don't have a programmer and don't know anybody near you who has one, well, in that case buying one is probably not a good idea. Unless you intend to fix some more mobos in near future, or use it for other purposes as well. Look for Xgecu T48 and decide if it's a price worth paying or if you'd rather look for a different mobo.