486 No Post, advice?

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486 No Post, advice?

Postby Aragorn » 2019-6-11 @ 09:31

As part of a bundle of bits i bought, i have a 486 motherboard that i cant get working.

The model number is "486ULD". Its had a leaky battery which i've removed, perhaps its terminally damaged some traces?

Anyway i've got it setup with a 486 DX2-66, a Trident ISA vga card and some ram. Upon power on it just gives one long beep, repeating forever.

I've stuck a POST card into it, and it flicks through some numbers before settling on "C1BE". Oddly the manual with the card is useless and only seems to give 2 digit codes, rather than the 4 digit code thats actually displayed. The LED's on the card seem sensible. -12, 12 and 5v are lit up as well as Frame, then reset lights for a short time, then reset goes out and CLK and IRDY comes on.

Any ideas before i give up and toss this board into the recycling?
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Re: 486 No Post, advice?

Postby Murugan » 2019-6-11 @ 12:38

Which BIOS is it?
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Re: 486 No Post, advice?

Postby Aragorn » 2019-6-11 @ 15:10

The Bios chip says "486 Award Software Inc"
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Re: 486 No Post, advice?

Postby TheMobRules » 2019-6-11 @ 15:36

What does the manual say for codes "C1" and "BE"?

The fact that the POST card goes through a bunch of numbers means it's executing BIOS code, that along with the error beep means that the motherboard is not completely dead at least. I wouldn't be so quick to trash it.

Also, if you can provide pictures of the areas affected by battery leakage we can have an idea of how bad the damage is.
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Re: 486 No Post, advice?

Postby Aragorn » 2019-6-11 @ 16:57

The booklet that comes with the tester says:

C1: OEM Specific - Test to Size On-Board Memory
BE: Program Chipset registers with power on BIOS defaults

I've tried different ram, and also no ram at all, and the error remains the same. The ram itself tests out fine on my other 486.
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Re: 486 No Post, advice?

Postby Aragorn » 2019-6-11 @ 17:02

Took a pic of the corrosion here:

https://photos.google.com/share/AF1QipN ... FkY1g5cll3

Its not the best pic but hopefully gives an idea.
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Re: 486 No Post, advice?

Postby Murugan » 2019-6-11 @ 17:07

Maybe a RAM problem?
Clean it up with white vinegar and IPA.
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Re: 486 No Post, advice?

Postby Aragorn » 2019-6-11 @ 17:10

as a test i tried my working 486 board also with a Award BIOS, with no ram installed, i get C6 C1. So certainly points to something going on with the ram i guess?

The ram itself is fine, are you suggesting cleaning the SIMM sockets with vinegar? I've gone over the whole area that had the battery corrosion with IPA already.
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Re: 486 No Post, advice?

Postby Murugan » 2019-6-11 @ 17:14

Is that picture before the cleaning :)?
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Re: 486 No Post, advice?

Postby Aragorn » 2019-6-12 @ 06:59

No that's afterwards.

I didn't clean the whole board, just that corner in the photo. There was a sort of scum on the board that didn't seem to shift even scrubbing with a toothbrush.
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Re: 486 No Post, advice?

Postby konc » 2019-6-12 @ 07:52

Are you certain that the memory you tried is FPM? Or 4 30-pin modules if you're not sure you have FPM modules.
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Re: 486 No Post, advice?

Postby Murugan » 2019-6-12 @ 08:44

There seems to be some damage near the ram slots. Do you have other sticks to test?
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Re: 486 No Post, advice?

Postby Aragorn » 2019-6-12 @ 10:00

I have 4 sticks in total, two originally came from this board, and two from another working 486 machine. All 72pin.

Both sets work in the other 486. Neither work in this one.
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Re: 486 No Post, advice?

Postby Murugan » 2019-6-12 @ 11:50

Hmmmm have you tried another videocard? Probably not the solution but hey :)
Still think it's RAM related...

TBH the area still looks "dirty" so a new clean with q-tip and vinegar? And after that IPA.
As stated before, the board still gives life so I would dig in a little further.
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