486SX motherboard won't POST, help

[da na]

Picked up a machine with a 486SX CPU and unknown motherboard w/no manufacturer markings. 5x 16 bit ISA, 1x 8 bit ISA, 1x EISA. I'm not getting +5 or +12 to the ISA slots, I am getting -12 and intermittently 3.3 according to my POST test card. No POST codes show on it. I assume something has gone wrong on the board side, since I would at least get a code if jumpers were wrong?

I've tried its PSU in a Packard Bell system and that worked, tried the Packard Bell's PSU in this and same issue. All traces seem intact, I've poked a few near the battery area and gotten signals. Had a Varta PRAM battery but I clipped it out, it does not seem to have exploded, leaked, etc yet. 

My best guess is the blue tantalum caps near the ISA slots, as those either hard short or open the circuit when they die, correct? I'd jump to bad electrolytics but the board has not a single one. 

Should I try the strategy of RAM removal and testing each chip in the first socket? It's also got cache slots, 6 of them... could those go bad, sitting in storage? Should I test those? 

[Bombastinator]

Old boards like that often used only beep codes.  Have you attached a speaker if there isn’t one already?  Also something that old can have odd problems not experienced my more modern hardware just because it’s old.  Some that come to mind are corrosion and galvanic action.  Dendrites could be a real problem.

[da na]

4 minutes ago, Bombastinator said:

Old boards like that often used only beep codes.  Have you attached a speaker if there isn’t one already?  Also something that old can have odd problems not experienced my more modern hardware just because it’s old.  Some that come to mind are corrosion and galvanic action.  Dendrites could be a real problem.

I get no audio thru the onboard speaker. I saw some corrosion on a single copper jumper and thought nothing of it, I will go back and check the rest, thanks!

[Guest]

Take whole clear high def pictures of the board please. I'd like to try and help identify it.  

[An0maly_76]

If the board is FUBAR, unfortunately, as I remember, lots of prebuilt manufacturers made their own boards back then and few, if any, interchanged. In those days, Tandy was pretty much out, Packard Bell was possibly an element in the nebulous formation of Hewlett-Packard, but on the ropes as a standalone manufacturer. Gateway miraculously managed to hold on until the late 2000s. There were a handful of lesser-known and no-name manufacturers that might have used more standardized generic boards. EP Technologies comes to mind, I had one of their 486SXs myself out of high school.

 

Is this meant to be a legacy machine for old MS-DOS games?

[da na]

10 minutes ago, Guest 5150 said:

Take whole clear high def pictures of the board please. I'd like to try and help identify it.  

Best I can do

[Guest]

15 minutes ago, Mel0n. said:

Best I can do

 

Uhg. 

 

Got an AGP slot... worth trying I think.

 

But first I'd strip it naked and throw it in the dishwasher. 

 

Then pull it and start cleaning all of the contacts.

 

Replace the battery. Or install a new one rather, you'd removed the old one already.

 

Then maybe try to get it to post. 

 

(looking for anything on this board, would like a back side picture too. But probably clean it up first will help the photos). *Still looking, but looks like it's an Intel board. 

[da na]

4 minutes ago, Guest 5150 said:

Uhg. 

 

Got an AGP slot... worth trying I think.

 

But first I'd strip it naked and throw it in the dishwasher. 

 

Then pull it and start cleaning all of the contacts.

 

Replace the battery. Or install a new one rather, you'd removed the old one already.

 

Then maybe try to get it to post. 

 

(looking for anything on this board, would like a back side picture too. But probably clean it up first will help the photos). *Still looking, but looks like it's an Intel board. 

That is eISA, not AGP

[Guest]

6 minutes ago, Mel0n. said:

That is eISA, not AGP

lol, right it's even written on the board. Sorry, got like 5 pages open with i486 boards right now, forgive me!! XD

[Guest]

Here's the list of 486 Chipsets

 

I can't read your's, so you may have the honor!

*this might help us narrow down the board.*

 

ETEQ ET6000 "Cheetah"

ETEQ ET9000 "Jaguar" single chip

OPTi 82C481/482 "HiB chipset", WriteThru

OPTi 82C491 WriteBack

OPTi 82C493 WriteBack

OPTi 82C495SLC/206Q, Write Back (2 chip, unbuffered VLB)

OPTi 82C495SX/392SX/206Q, Write Back (3 chip, buffered VLB for improved compatibility but slower performance)

OPTi 82C495XLC/206Q, Write Back (2 chip)

OPTi 82C496[A,B]/497/206 (2 or 3 chip, 497 is optional cache controller)

OPTi 82C571/82C572 VLB, ISA "486/Pentium Writeback" (Hybrid 486/586 design, 64-bit SRAM, 32-bit DRAM)*SiS 401/402 ISA

OPTi 82C682, 386/486WB EISA chipset

OPTi 82C683, 386/486AWB EISA chipset

OPTi 82C802G ISA,VLB (single chip version of 82C895)

OPTi 82C895/82C206 ISA,VLB

SiS 401/402 ISA

SiS 406/411 EISA, VLB

SiS 460 ???

SiS 461 ISA, VLB

SiS 471 ISA, VLB

SiS 496/497 ISA, VLB, PCI

Symphony "Haydn"

UMC UM82C491/82C493 ISA,VLB

UMC UM8496/8498 ISA, VLB

UMC UM8881/8886 ISA, VLB, PCI

VIA VT82C496/82C505/82C406 ISA, VLB, PCI

[da na]

2 minutes ago, Guest 5150 said:

Here's the list of 486 Chipsets

 

I can't read your's, so you may have the honor!

*this might help us narrow down the board.*

 

ETEQ ET6000 "Cheetah"

ETEQ ET9000 "Jaguar" single chip

OPTi 82C481/482 "HiB chipset", WriteThru

OPTi 82C491 WriteBack

OPTi 82C493 WriteBack

OPTi 82C495SLC/206Q, Write Back (2 chip, unbuffered VLB)

OPTi 82C495SX/392SX/206Q, Write Back (3 chip, buffered VLB for improved compatibility but slower performance)

OPTi 82C495XLC/206Q, Write Back (2 chip)

OPTi 82C496[A,B]/497/206 (2 or 3 chip, 497 is optional cache controller)

OPTi 82C571/82C572 VLB, ISA "486/Pentium Writeback" (Hybrid 486/586 design, 64-bit SRAM, 32-bit DRAM)*SiS 401/402 ISA

OPTi 82C682, 386/486WB EISA chipset

OPTi 82C683, 386/486AWB EISA chipset

OPTi 82C802G ISA,VLB (single chip version of 82C895)

OPTi 82C895/82C206 ISA,VLB

SiS 401/402 ISA

SiS 406/411 EISA, VLB

SiS 460 ???

SiS 461 ISA, VLB

SiS 471 ISA, VLB

SiS 496/497 ISA, VLB, PCI

Symphony "Haydn"

UMC UM82C491/82C493 ISA,VLB

UMC UM8496/8498 ISA, VLB

UMC UM8881/8886 ISA, VLB, PCI

VIA VT82C496/82C505/82C406 ISA, VLB, PCI

Looks like it says "Uni U4800"

Vintage uni u4800-vlx at isa vlb motherboard + AMD 486 dx-40 + 16 mb ram works! | eBay

This is a very similar one

[Guest]

1 minute ago, Mel0n. said:

Looks like it says "Uni U4800"

Vintage uni u4800-vlx at isa vlb motherboard + AMD 486 dx-40 + 16 mb ram works! | eBay

This is a very similar one

I source EBAY TOO!!!!!

 

Here this one looks closer. AUVA? never heard of it XD. 

 

Long link click this instead

[da na]

2 minutes ago, Guest 5150 said:

I source EBAY TOO!!!!!

 

Here this one looks closer. AUVA? never heard of it XD. 

 

Long link click this instead

Closer but way too long lol. 

[Guest]

Just now, Mel0n. said:

Closer but way too long lol. 

You know, I never really realized how many board manufacturers there are. There's millions it seems.

 

The chipset number brings up a single thread. 

https://www.vogons.org/viewtopic.php?t=48881

 

So I looked up the board dude is talking about in that thread. 

 

Then I found this awesomely long list..... Socket 2 and 3. 

https://stason.org/TULARC/pc/motherboards/m486_t.html

 

Then I decided to stop clicking around and let you do that part!!! 

 

Good luck, cause you're gonna need it.

P.S. I would bookmark that page actually. In fact I think I'm going to myself.

~Jon

 

[da na]

1 minute ago, Guest 5150 said:

You know, I never really realized how many board manufacturers there are. There's millions it seems.

 

The chipset number brings up a single thread. 

https://www.vogons.org/viewtopic.php?t=48881

 

So I looked up the board dude is talking about in that thread. 

 

Then I found this awesomely long list..... Socket 2 and 3. 

https://stason.org/TULARC/pc/motherboards/m486_t.html

 

Then I decided to stop clicking around and let you do that part!!! 

 

Good luck, cause you're gonna need it.

P.S. I would bookmark that page actually. In fact I think I'm going to myself.

~Jon

 

weird thing is it's got 3 sockets - 386, 387, 486...

[Guest]

1 minute ago, Mel0n. said:

weird thing is it's got 3 sockets - 386, 387, 486...

I noticed that, but seen it before. So it didn't look too weird. Back then everything was compatible with everything. 

 

Maybe test the clock circuit. If you have nothing the RTC chip is probably fubar. Maybe you could replace it. (just tossing an idea for testing)

[Guest]

Get anything going yet on this board? Just curious, you know me, I like the vintage stuff too!

[da na]

2 hours ago, Guest 5150 said:

Get anything going yet on this board? Just curious, you know me, I like the vintage stuff too!

Had tons of work this week so not fixed yet. But I have tested capacitors on the board and about 1/3 of them are hard shorted or have really high ESR. Poked a few traces and they all seem intact. Tried putting 3.3v? 5v? can't remember what it was but the battery voltage back through the battery pins and still no life. Don't have the balls to plug it into the PSU and poke around while stuff is live, even at 5v - hands are too shaky...

[Guest]

17 minutes ago, Mel0n. said:

Had tons of work this week so not fixed yet. But I have tested capacitors on the board and about 1/3 of them are hard shorted or have really high ESR. Poked a few traces and they all seem intact. Tried putting 3.3v? 5v? can't remember what it was but the battery voltage back through the battery pins and still no life. Don't have the balls to plug it into the PSU and poke around while stuff is live, even at 5v - hands are too shaky...

Well not a bad idea to check stuff with the PSU plugged in. You can't check everything on ohms alone. Shaky hands, I can't help you with  

[Pasi123]

On 8/18/2022 at 1:54 AM, Mel0n. said:

Best I can do

The Retro Web seems to have that board but there isn't much info about it

 

https://theretroweb.com/motherboards/s/sidus-386-486c64l-sid

[da na]

1 hour ago, Pasi123 said:

The Retro Web seems to have that board but there isn't much info about it

 

https://theretroweb.com/motherboards/s/sidus-386-486c64l-sid

Yeah, someone on Vogons pointed me to this site. Hopefully I can find out more and add more info to this site