https://theretroweb.com/motherboards/s/shuttle-hot-685

It should be sporting an Intel chipset if the silkscreen is correct (440BX)

Model on yours is 685V12A, probably not relevant but it's close enough.

Beeps should be ram related, reseat ram stick if no go clean with some deoxit (contact cleaner) or change ram slot.
Also clean the contacts on the ram stick, some alcohol or an eraser will do.

Did you install a CMOS battery after you took the photo? Some motherboards won't POST without one.
If you have a PCI video card, I'd try that. That motherboard may be very selective about what AGP video cars will work - low power AGP slots were pretty common back then. I'd also try another power supply if you have one. You can use the case's reset switch as the power switch if you use an ATX PSU.

andreipasca wrote on 2023-09-13, 15:38:

It posts long continuous beeps. And I have no idea what the POST codes mean as I have no clue what model and make is the Mobo.

Nexxen had already identified the MoBo for you, but even if he didn't you should be able to see the shiny Award sticker on the BIOS chip at lower left corner. POST beep codes can be found online with a quick search; long continuous beeps mean your RAM strip might be faulty: not seated properly, oxidized contacts, corrupted chips, etc. I'd start with using deoxidizing contact cleaner on both the DIMM and the slots; if you have more SDRAM modules around then test the system with different strips.

Nexxen wrote on 2023-09-13, 15:42:

https://theretroweb.com/motherboards/s/shuttle-hot-685 […]
Show full quote

https://theretroweb.com/motherboards/s/shuttle-hot-685

It should be sporting an Intel chipset if the silkscreen is correct (440BX)

Model on yours is 685V12A, probably not relevant but it's close enough.

Beeps should be ram related, reseat ram stick if no go clean with some deoxit (contact cleaner) or change ram slot.
Also clean the contacts on the ram stick, some alcohol or an eraser will do.

I have seen the model before but no results came up on Google. So I figured it's an OEM board that has the same/similar layout as one from conventional brands. Already cleaned the DIMMs and the slots. I've tried booting it with the old CMOS battery and without one. Will try with a new one.

Nexxen wrote on 2023-09-13, 15:42:

https://theretroweb.com/motherboards/s/shuttle-hot-685 […]
Show full quote

https://theretroweb.com/motherboards/s/shuttle-hot-685

It should be sporting an Intel chipset if the silkscreen is correct (440BX)

Model on yours is 685V12A, probably not relevant but it's close enough.

Beeps should be ram related, reseat ram stick if no go clean with some deoxit (contact cleaner) or change ram slot.
Also clean the contacts on the ram stick, some alcohol or an eraser will do.

Ok, I cleaned it again with deoxit, swapped the CPU with another Celeron, all same. Then swapped back to the original Celeron CPU. Now when I insert the RAM in the first DIMM it gives me the long beeps but when I insert it in the third DIMM I get one long and three short beeps. What could it be?

My take would be that one RAM slot has issues, and when you use the other then you get as far as an issue with the video card. So I'd leave it in the slot where you get one long and three short, then try a PCI video card.

Repo Man11 wrote on 2023-09-14, 00:42:

My take would be that one RAM slot has issues, and when you use the other then you get as far as an issue with the video card. So I'd leave it in the slot where you get one long and three short, then try a PCI video card.

From ram to video, that's progress! 😀
Yes, PCI card if he has one.

I think he's getting closer to a working system.

Nexxen wrote on 2023-09-14, 01:23:

From ram to video, that's progress! :) Yes, PCI card if he has one. […]
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Repo Man11 wrote on 2023-09-14, 00:42:

My take would be that one RAM slot has issues, and when you use the other then you get as far as an issue with the video card. So I'd leave it in the slot where you get one long and three short, then try a PCI video card.

From ram to video, that's progress! 😀
Yes, PCI card if he has one.

I think he's getting closer to a working system.

I have magically managed to make it work with that RAM bar in DIMM 2 and a S3 video card. It turned on and booted. Then I connected the HDDs (some weird wide socket HDDs not IDE that connect via a PCI adapter), CD ROM, and the serial/parallel/etc expansions via MoBo sockets. Now it's not displaying anything again. Any tips?

andreipasca wrote on 2023-09-14, 10:17:

Nexxen wrote on 2023-09-14, 01:23:

From ram to video, that's progress! :) Yes, PCI card if he has one. […]
Show full quote

Repo Man11 wrote on 2023-09-14, 00:42:

My take would be that one RAM slot has issues, and when you use the other then you get as far as an issue with the video card. So I'd leave it in the slot where you get one long and three short, then try a PCI video card.

From ram to video, that's progress! 😀
Yes, PCI card if he has one.

I think he's getting closer to a working system.

I have magically managed to make it work with that RAM bar in DIMM 2 and a S3 video card. It turned on and booted. Then I connected the HDDs (some weird wide socket HDDs not IDE that connect via a PCI adapter), CD ROM, and the serial/parallel/etc expansions via MoBo sockets. Now it's not displaying anything again. Any tips?

The power supply is ancient, and was probably barely adequate when it was new, so it could very well be the culprit.

Do you have a multimeter? If so, try checking the +5V and +12V voltages from one of the unused drive connectors.

That's an unusual board. Not many socket 370 motherboards have AT power connectors. Those were obsolete when this board was new. They would have only been included to encourage upgrades for people who already had an old power supply.
Depending how the board is designed, an ATX power supply might help it to work better with more video cards. That's because ATX power supplies provide 3.3V and AT power supplies don't.

shamino wrote on 2023-09-14, 11:54:

Do you have a multimeter? If so, try checking the +5V and +12V voltages from one of the unused drive connectors.

That's an unusual board. Not many socket 370 motherboards have AT power connectors. Those were obsolete when this board was new. They would have only been included to encourage upgrades for people who already had an old power supply.
Depending how the board is designed, an ATX power supply might help it to work better with more video cards. That's because ATX power supplies provide 3.3V and AT power supplies don't.

Not uncommon, these were about the last consumer platforms to be on baby AT.

Here's a similar board, a Luckytech P6VBX7. Note the AT and ATX connectors. As for running them off AT PSUs, I can say mine does work fine off an 200W AT PSU, though I've had mine recapped entirely after experiencing issues similar to OP.

So to answer OP's issue - replace ALL capacitors on the board with good new caps and it should work.

I won't recommend to use AT power supplies with AGP video cards on these kind of boards (also SS7 boards).

As long as the PSU does not supply 3.3v, there is a VRM phase to do that and it can get easiliy overloaded with everything more powerful than let's say a GF2 MX or similar.

Better use ATX power supplies that can deliver 3.3V on their own to be safe.

shamino wrote on 2023-09-14, 11:54:

That's because ATX power supplies provide 3.3V and AT power supplies don't.

and this does not affect dual-power motherboards at all.
If there is an AT power connector, then the motherboard always has a converter from 5V to 3.3V, and always uses it, even with ATX PSU.
PS. Some have jumpers “to bypass the built-in converter,” but it would be better not to have them, it’s so crookedly implemented.

mmx_91 wrote on 2023-09-14, 13:58:

I won't recommend to use AT power supplies with AGP video cards on these kind of boards (also SS7 boards).

As long as the PSU does not supply 3.3v, there is a VRM phase to do that and it can get easiliy overloaded with everything more powerful than let's say a GF2 MX or similar.

Better use ATX power supplies that can deliver 3.3V on their own to be safe.

I've run both an GF2 MX and a GTS on that mobo using an 200W ASTI LC-200C PSU I rebuilt with no issues. Both on the P6VBX7 and a P5MVP3.
Neither had any issues with either cards. They also ran Geforce 4 MX and Ti4200 cards with no issues, using the same PSU.

And just as shevalier said it - these have a converter that likely takes 5v and steps it down to 3.3, and that thing will run regardless whether it's running from AT or ATX power. Most of these AT 370/Slot1 designs are made to do so.

As I said, it depends how the motherboard is designed. They're not all the same, and we don't have his board in front of us to probe out with a meter.
Some dual power boards do in fact draw power from the 3.3V pins of the ATX connector, and they don't all even need a jumper to do it.

Obviously boards like this have an onboard 3.3V regulator, but they are notoriously inadequate. That regulator could be in poor working condition, as could be the AT power supply which were problematic in the AGP era and which few socket-370 boards even tried to support.
He's having trouble with AGP video cards which happen to be a major power consumer.
Power should always be checked and verified on any PC, but especially one that is having issues. 5V and 12V are easy to check, 3.3V isn't much harder.

What I'd check would be the caps. Those are 20+ years old caps.

PcBytes wrote on 2023-09-14, 22:03:

What I'd check would be the caps. Those are 20+ years old caps.

Nope, that's 20+ years of LOW QUALITY caps... nuance there not negligeable 😀
This is PCChips level, good it didn't blow in his face straight off.

OK....new problem. So I managed to boot into Windows 2000 setup (Windows 2000 SP4 Final Edition 2011). Windows 2000 detects IDE HDD, BIOS also does. It finishes copying the files for installation, restarts, and loops. If i manually try to prioritise booting from HDD it tells me to insert install disk... Windows 98 setup directly tells me that i do not have a hard disk. The PC originally came with one IDE and two SCSI drives that connect through a SCSI PCI adapter. any idea what to do?

andreipasca wrote on 2023-09-15, 00:58:

The PC originally came with one IDE and two SCSI drives that connect through a SCSI PCI adapter. any idea what to do?

SCSI adapter -> to shelf.
And testing RAM. Bay the way which CPU and which FSB you run on its matherboard ?

shamino wrote on 2023-09-14, 21:24:

Some dual power boards do in fact draw power from the 3.3V pins of the ATX connector, and they don't all even need a jumper to do it.

Yep, i.e. CUBX-L. 😀
There not solder DC/DC and has 4 solder wire from ATX rail to matherboard 3.3V.
Rumors that there are some special boards that determine everything themselves and switch the power supply are urban legends.
Nowadays, many motherboard schematics have leaked online. Everything is much more boring and banal, alas.