Electronics > Repair
What more i can do?
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asis:
here
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--- Quote from: 222Lab_Test222 on December 09, 2024, 07:07:32 am ---
Could you measure both Vout by multimeter on working and not working.
Also please measure +5volts at the same EPROM pins on both.

--- End quote ---
Working Board
-Vout 3.57V

Non Working Board
-Vout 3.61V
[/quote]
=
The CPU has no dynamic load, so Vout is 3.61V (it consumes almost nothing).
222Lab_Test222:

--- Quote from: Harry_22 on December 09, 2024, 07:11:38 am ---And 5.00 ?
Reduce 3.61 up to 3.45

--- End quote ---
I would say 4.9 and some points
How to reduce it?
If i reduce 5V to around 4.5 it beeps in working board, the minimum volt is 4.6.
Harry_22:
So I have completed a comparative analysis of the Addresses supplied to the EEPROM and the Data read.
On the faulty board identical Chip Select, Read and Address signals are traced within eight clock cycles but the output data is different.

On the working machine the data sequence is ODE9h, 00F8h, 0000h, 0000h...
On the not-working is 0D0Dh, 0000h, 0000h...

Colleagues, what are your thoughts?
Harry_22:
Remove IC16 (Low EPROM) and look the signals on the data bus.
Please post here the tracks D0, D2 and D5.

We check for the presence of extraneous signals on the data bus freed from IC16.

PS
Try diagnosing another board using our experience.
222Lab_Test222:

--- Quote from: Harry_22 on December 10, 2024, 06:41:19 pm ---Remove IC16 (Low EPROM) and look the signals on the data bus.
Please post here the tracks D0, D2 and D5.

We check for the presence of extraneous signals on the data bus freed from IC16.

PS
Try diagnosing another board using our experience.

--- End quote ---

IC16 removed, here are outputs of DO D2 and D5. Its the working board.
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