First post, by adalbert
Hello,
few months ago I got an untested Am386DX-40 mainboard (Unichip 367c, or 386WB), which apparently had suffered a battery leak. It didn't turn on, it had some traces covered with rust and green substance. I washed it in distilled water with citric acid, then cleaned it with alcohol but it didn't help. Recently i desoldered keyboard controller, keyboard connector, PSU connector and all memory slots. I fixed 4 or 5 traces using a wire. I checked other suspicious traces with multimeter but most of them would conduct electricity even when they were covered with rust, so I put some solder on them, to regenerate and protect them. Then I soldered one memory bank and power connector. I soldered a socket for keyboard bios.
Now, after turning the power on, i get some sound from PC speaker! I get two fast, high pitched beeps, then 8 lower pitched beeps. It has AMI bios, so it suggests video problem. But i tested it with two video cards and it doesn't work. I tested these video cards with ultra-low-end 386SX PC chips mainboard (it has got only chipset, bios and CPU 😜 and the PCB doesn't have any internal layers, i can't imagine cheaper construction) and they work. And when I start that PC-chips board without video card, it gives exactly the same beep code (it also has AMI bios).
Does anybody have idea how could I fix that? Does that beep code mean that it must be video problem? If so, then i would check connections between ISA slots and the rest of hardware. But that error can still be caused by other factors, like memory or cache?
This is the error sound.
With one or more memory modules missing the error sound is different (repeating 3 low pitched beeps), so apparently the mainboard is detecting the memory.
Repair/electronic stuff videos: https://www.youtube.com/c/adalbertfix
ISA Wi-fi + USB in T3200SXC: https://www.youtube.com/watch?v=WX30t3lYezs
GUI programming for Windows 3.11 (the easy way): https://www.youtube.com/watch?v=d6L272OApVg