First post, by PC@LIVE
TK-82C390A-4N-D11SE 386DX motherboard test, 128KB L2 cache, UMC chipset, 4MB RAM 30PIN, AMI BIOS.
In recent days I have fixed the two broken tracks of the socket for the keyboard plug.
The work was not complicated, the tracks are large, then I changed the socket for the keyboard with another (recovered), finally I soldered 2 wires for the new 3.6V battery, this serves to distance it, and avoid in case of loss, further damage.
By connecting the indispensable ie Power Supply. ISA Video Card, ISA POST CARD, ISA Keyboard and Controller, I try to start and it seems to be ok, but at some point it starts to beep, counting them are six, which correspond to an error of the keyboard controller 8042 - Gate A20.
The beeps start when the post card shows 08 07 in the display, then they continue and the card changes display passing to 00 08, a sign that something still manages to do, unfortunately at this point there is no display of any video signal.
I remove after turning off the keyboard plug, and restart, now the post card shows various codes in the display and the six beeps are no longer heard, but then it stops at 43 42 and starts to beep continuously, also I have a video signal in which I can read SYSTEM HALTED, I guess it is preceded by FATAL ERROR, the 43 corresponds to Detect Initialize Port, here it stops whether the ISA controller is present or removing it.
Returning to the problem of the Keyboard controller 8042, in this MB the chip is signed LT38C41, I do not know if it is an equivalent chip and if it is a programmable chip, in any case if he was the cause of the problem (the six beeps), I would have a chip of a motherboard 386DX scrapped in the years 2000, this is signed NEC 8907P7 D80C42C161 ATI KBD-3, if it is compatible and does not require special programming could I try it ??? The chip is like pinout identical, but I don't know if it's the same electrically.
Unfortunately not being able to view any BIOS screen, I can't see the make and model of the motherboard, this could be useful to check the jumpers, in case there is some wrong setting, from a search I did it is very similar to Gigabyte GA-386UM 33/40, but some jumpers (near the battery) seem to be different, then there is a J8 which here is W9, the W9 has no jumper (should it be put?) And the serigraphs read ON-Color. ..
AMD 286-16 287-10 4MB HD 45MB VGA 256KB
AMD 386DX-40 Intel 387 8MB HD 81MB VGA 256KB
Cyrix 486DLC-40 IIT387-40 8MB VGA 512KB
AMD 5X86-133 16MB VGA VLB CL5428 2MB and many others
AMD K62+ 550 SOYO 5EMA+ and many others
AST Pentium Pro 200 MHz L2 256KB