Two screenshots attached.
Colin.
Quote:
Originally Posted by ortek_service
No pressing of keys is required, as just need to test the control of the keyboard rows-scanning outputs, that is done by the Kernal ROM
- So need that one in place, and it booted into BASIC's normal operation.
However, you only really need to probe 1 or 2 pins, as it's been possible from the fault symptoms to narrow this down to the least-significant bit of the 4 BCD lines into the UC9 74LS145.
So only really need to (as suggested in the 2 posts prior to the previous one):
Probe the 'KEYA' line at: UC9 (74LS145) Pin 15 ('A' input)
& (particularly if no activity there) also: UC7 (6520) Pin 2 (PA0)
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