Electronics > Repair

What more i can do?

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m k:

--- Quote from: Harry_22 on December 04, 2024, 10:14:10 pm ---Here are the Address and Data pictures of the first 20us for the working machine.
The first address is 3FFF8h.
The comparison for non-working machine I will make next.

--- End quote ---

My guess is that your address is one off.
A0 is actually A1 and real A0 is not present.
So ROM address for boot goes to correct address 7FFF0.

A bit after first jump is IN 35h.
Pictured A4 is dropping down after a jump and single high is 35h.

Jump address is F800, so A11 stays up.
35h has A5 and A4 up and A0 is missing.

m k:

--- Quote from: 222Lab_Test222 on December 04, 2024, 04:40:59 am ---Working Board Address Inputs Wa0-Wa9

--- End quote ---

If you like you can check that A4 of all faulty boards.
If shape is the same you have functioning connection between CPU and program ROM.

If that single high is not there you have a similar fault that the original test subject has.

222Lab_Test222:

--- Quote from: m k on December 26, 2024, 12:16:59 pm ---
Why did you scope only half of the data?

--- End quote ---
Half the data mean?

222Lab_Test222:

--- Quote from: m k on December 26, 2024, 06:06:59 pm ---
If you like you can check that A4 of all faulty boards.
If shape is the same you have functioning connection between CPU and program ROM.

If that single high is not there you have a similar fault that the original test subject has.

--- End quote ---
If I do not get similar signals then that hints CPU is faulty?
Or is there any way to know CPU is ok or not.

asis:
Hi,

If you have time, check the circuit by ringing the connections.
Please.
-
Next step will be - FRAM/ DRAM SIMM72.

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