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What more i can do?

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222Lab_Test222:
These above all are working board images.

Now below are non working board images.

Only 3 of them are different so i am sending only 3 of them.
They are
-74ls174 1 pin
-74ls174 9 pin
-74f74 9 pin

222Lab_Test222:

--- Quote from: Harry_22 on November 14, 2024, 07:26:50 am ---Ring the Reset signal from CPU to D1 Power supply monitor. It passes via some 74... logic

Also ring the path of CLK CPU signal.
Draw the scheme or mark them on the top PCB layer picture.


--- End quote ---

The CLK and RESET signals as well as many pins of CPU and other RTC ICs, 74LS ICs, EPROMS all connected to the WACOM IC WE001BF.

Harry_22:
Thank you very much for your careful measurements!
The summary in pictures you will find below.

You have found a small thread in the processor control logic (see the last screen in the second picture). The main thing is that this thread leads to the root cause.

Please measure the other signals on the pins of this D-type flip-flop.

Doctorandus_P:
My guess is they may have "hidden" some kind of key in the CMOS ram.

And for the rest, what sort of thing is that? It looks like a regular old PC board with some extra I/O. Maybe it's feasible to just replace it with more modern hardware. Maybe you can put it on a modern board, put the thing in a VM and redirect I/O. Modern hardware is so gianormous more faster then the old stuff that you have gazillions of cpu cycles to play with.

Poroit:
G'day Doctorandus_P,

Brochure attached of the system.

This PC board is part of the controller for the Underground Drilling Machine.

Over 30 years old so if you can think of a method of modernising it, I am sure the OP would be interested.

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