UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Non-working Commodore PET 3016

ortek_service · 11th Apr 2021, 1:37 am

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)

11th Apr 2021, 1:37 am	#1548
ortek_service Octode Join Date: May 2018 Location: Northampton, Northamptonshire, UK. Posts: 1,440	Re: Non-working Commodore PET 3016 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)