VOGONS


First post, by incanus

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I've acquired a late-80s portable 386 with builtin LCD in unknown working state. It only ever beeps continuously on boot, with no picture on either the built-in LCD or an external VGA-connected monitor. It's not a series of beeps, but one, long, very loud beep forever.

Relevant details: 386SX-16, AMI BIOS, SIMMx4 and DIPx36 (8MB, I believe; I'm having trouble locating the chips online).

I've desoldered and cleaned up a leaking rechargeable 3.6V CMOS battery and tried replacing it with a coin cell to the appropriate headers w/ jumper setting for external battery.

I've tried pulling all the RAM in various combinations (obeying the manual's instructions about which banks to leave empty when doing so and how to set jumpers). If I remove all RAM, there is no beep.

At the base level, I'm trying these things with the external CMOS battery and the video card hooked up, but I've removed all the other ISA cards: serial/parallel, disk controller, and a NIC.

I've confirmed that the AT power supply has proper ground, +/-5V, and +/-12V, and the fan is coming on when it is hooked to the system. I've tested with another AT power supply.

There are two BIOS chips (even and odd, in mobo sockets marked low and high) and an "AMI Keyboard BIOS Plus" chip near the AT keyboard connector. I reseated the pair of BIOS chips. If remove the keyboard BIOS chip, there is a different, quieter, higher-pitched continuous beep.

I am fairly certain the previous owner would not have messed around inside of things, so I'm suspecting bad component(s) because of age or other happenstance.

What should I try next? Any ideas on what else could be wrong?

Last edited by incanus on 2020-05-26, 19:05. Edited 1 time in total.

Reply 2 of 9, by incanus

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I have not. I don't have access to any just yet; this is my only vintage machine. I did try removing the 4 SIMMs (to try the 36 DIPs), then removing the second bank of 18 DIPs, then removing all the DIPs and trying each combination of two of the 4 SIMMs. I set the six corresponding jumpers appropriately during each change according to the motherboard manual. Basically, I tried to make the best of what I did have on hand.

Reply 3 of 9, by incanus

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I've confirmed that the VGA card and LCD are working properly by:

- Putting the VGA card in a working ATX machine & connecting the LCD
- Powering the LCD bus on the VGA card from its original AT power supply, which has special connections for +12V and -22V
- Tying the ATX & AT power supply grounds

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ATX hosting VGA card, AT powering LCD
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VGA card BIOS DIP error
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ATX computer running on LCD
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I'm currently suspecting bad traces or corrosion damage to the AT motherboard in the original computer. I have a diagnosis tool arriving soon and will see if that gets me any further, then I may try repairing traces and/or verifying no shorts on the motherboard (though that's all new to me).

Reply 4 of 9, by incanus

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Miraculously, I managed to repair and boot this sucker! It was indeed bad traces. I identified two that didn't have continuity and repaired them.

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I was then able to piecemeal test all the RAM, all the way back up to the 36 DIPs and 4 SIMMs at 8MB. Reassembled everything and it booted!

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Got an old ISA SB AWE32 into it (just barely, due to the size constraints) and figured out how to run the weird VGA card on either the internal mono LCD or an external VGA monitor.

That escalated quickly.

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More to follow on this unique machine. This truly was a success story that I did not expect to have.

Reply 5 of 9, by Horun

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Good work ! Amazing actually !

Hate posting a reply and have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor. 🤣 Second computer a 286 12Mhz with real IDE drive ! After that came 386, 486, Pentium, P.Pro and everything after....

Reply 6 of 9, by luckarusky

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incanus wrote on 2020-05-26, 18:57:
Miraculously, I managed to repair and boot this sucker! It was indeed bad traces. I identified two that didn't have continuity a […]
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Miraculously, I managed to repair and boot this sucker! It was indeed bad traces. I identified two that didn't have continuity and repaired them.

traces.jpg
repair.jpg

I was then able to piecemeal test all the RAM, all the way back up to the 36 DIPs and 4 SIMMs at 8MB. Reassembled everything and it booted!

boot.jpg

Got an old ISA SB AWE32 into it (just barely, due to the size constraints) and figured out how to run the weird VGA card on either the internal mono LCD or an external VGA monitor.

That escalated quickly.

doom.jpg

More to follow on this unique machine. This truly was a success story that I did not expect to have.

Now that is cool! How well does Doom play?

Reply 7 of 9, by incanus

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It's not super playable except at a tiny viewport size, since this is a 16MHz / 8MB RAM / 256K VRAM machine, but it was fun to launch. I have a 2000-era P3 that is just fine if I want to get my fix. I'm mostly using the 386 right now for experimenting with MS-DOS, serial comms, CGA games, custom peripheral design, and Turbo Pascal. I got a hold of a SoundBlaster 16 Vibra that I've swapped in for the SB AWE 32 (which went back to the P3) to free up some physical space in the case while still sounding good.