>beeps once

wait, what exactly is beeping once? speaker? then ISA bus is broken preventing POST card from showing codes

I'm using a DEC LK450-AA apha station terminal keyboard... it beeps when it turns on, and every key press makes a "tick" sound to simulate a typewriter

It's normal for that keyboard, I don't have another PS2 keyboard at the moment

Thanks I'll keep checking the ISA bus.

You mentioned you’ve checked reset voltages and ICs, but didn’t mention reset behaviour on the post test card?

Does it show life at all?

Do you have valid clock signals? Nothing getting warm would suggest nothing is running.

MikeSG wrote on 2023-12-10, 15:21:

I'm using a DEC LK450-AA apha station terminal keyboard... it beeps when it turns on
Thanks I'll keep checking the ISA bus.

ah, forget about ISA then
CPU isnt running
or cant reach Bios
or Bios is corrupted

MikeSG wrote on 2023-12-10, 03:35:

Hi, I've been repairing a Chips & Tech 386DX PEAK-DM board for the last few weeks-months, and not sure what else to try next. Ca […]
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Hi, I've been repairing a Chips & Tech 386DX PEAK-DM board for the last few weeks-months, and not sure what else to try next. Can anybody give me any options to try?

This is the board:
https://theretroweb.com/motherboards/s/biostar-mb-1333c-ch
https://theretroweb.com/motherboards/s/biostar-mb-1333c-ch-b

Biostar MB-1333C/40C-CH 386DX PEAK DM/386

Symptoms/efforts:
1) BIOS Post Analyser Codes: nothing. CLK, IRDY, FRAME light up normally.
2) Keyboard lights flash once/beeps once. Normal. Keyboard Controller works.
3) Reset BIOS/CMOS: no difference.
4) Checked entire RESET1-4 circuit voltages. All fine.
5) After 2 mins: CPU & BIOS are still cold. Other chips, cache, RAM are warm. Keyboard Controller and the M74F245P chip next to the varta corrosion are the warmest.
6) Fixed multiple corroded lines. Reset IC chips, RAM, BIOS, CPU in their socket multiple times. New BIOS W27C512. Known working RAM.

Should the CPU & BIOS be warm after 2 mins?

I ordered new 74F245 chips as well as the ones next to it near the varta corrosion. If all those are fine and no corroded lines underneath what else is there to test?

Necroware has this video of him repairing a 386 board. It wasn’t posting. I think the issue were the jumpers not set correctly. https://youtu.be/CrD6hALcbkc?si=KLZeBLL9wH4rvAj-

paradigital wrote on 2023-12-10, 15:36:

You mentioned you’ve checked reset voltages and ICs, but didn’t mention reset behaviour on the post test card?

Does it show life at all?

Do you have valid clock signals? Nothing getting warm would suggest nothing is running.

Post card analyser Reset light: Light flashes on briefly when you turn the power on, then turns off (normal).

Post card analyser, all lights: +12v, -12v, +5v, CLK, IRDY, FRAME - all solid lit.

I need to actually check under IC's near the battery corrosion, there's some chips/lines there connected to the ISA bus

Checked jumpers many times and matched them to the manual & other boards