Electronics > Repair
What more i can do?
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222Lab_Test222:

--- Quote from: Harry_22 on December 16, 2024, 01:09:54 pm ---
--- Quote from: 222Lab_Test222 on December 16, 2024, 12:18:24 pm ---
just check with hands? Whats a little in out things, i do not understand, i saw the picture BUT still unclear.

--- End quote ---

I suppose that the reason may be in the weakened contacts of the DIP-circuit bushings under IC16.

I would advise you to take any DIP chip, bend one leg and try the clamping force of the contacts one by one.
If all the contacts are tight, spray them with contact cleaner and go around in a circle with this chip making an in-out.

It would be better to change the entire IC panel, but only do this if my guess is confirmed.

--- End quote ---
I check Pins one by one and use a small needle to open contacts. BUT it is still same.
I double confirm it with multimeter and the clamps are seems connected and shorted..
222Lab_Test222:

--- Quote from: asis on December 18, 2024, 03:33:32 am ---Hi,

@222Lab_Test222


Could you please read the inscriptions (if any) on the uPD4990 on the working PCB(s) indicating the batch number and year of manufacture and compare them with the inscriptions on the IC23 chips on all the non-working PCBs.

I suspect that this is a "2000Year" problem.

If you are confident in yourself, you can move the chip from the working board to the non-working one (or vice versa).

--- End quote ---
The working IC name is NEC D4990A 9626F7.
The non working IC name is NEC D4990A 9344F7. The non working one is the new one I just changed recently.
222Lab_Test222:

--- Quote from: m k on December 16, 2024, 10:30:56 am ---
--- Quote from: 222Lab_Test222 on December 16, 2024, 07:54:45 am ---Did it (EPROMS DATAs) says or shows anything regarding where the issues are?  :scared:

--- End quote ---

No.

Do the swap and new scoping and do them exactly like before.

--- End quote ---
After the High and Low EROMS swap in Non Working Board.
u666sa:
Quit
Valuable lesson learned. You have to know when to quit.
squadchannel:

--- Quote from: u666sa on December 18, 2024, 08:04:31 am ---Quit
Valuable lesson learned. You have to know when to quit.

--- End quote ---
Exactly.

with LA(logic analyzer), you might be able to find address pins or data pins that are not working, but that's all you can do with scope.
I don't even know where the uploaded image shows, and few people would go back 20 pages to try to understand it. :palm:

my thought is that the PAL/GAL is damaged, or via/trace is damaged. I could also consider a reset IC and RTC. :-//

if you wanted to run Komatsu machines at all costs, I would replace it with a modern motherboard. since it seems to be just an ISA bus.
COM-Express or ATX, ISA bridge and custom pcbs.
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