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

ortek_service · 25th Apr 2021, 8:23 pm

EDIT: Just saw your reply after I was typing the below. Had you removed UC7 before the fault happened by mistake?
- As I thought UC5 (6522) was being being removed, to lift Pin14.

However, I think the CASS SENSE switch reading may be involved, so there may be some other things to check
(Possibly swapping-over the 6520's)

---------

Is that with all pins of the 6522 inserted ? / Is there a chance the wrong one has been lifted?

It seems the 6522's internal timers may be used by the Kernal for keyboard scan etc. periodic interrupts and could be some odd effects if not running correctly.

Otherwise, it does seem it's mostly running OK some of the time, to get that far. And maybe an intermittent connection on an IC socket etc. somewhere (like with previous occasional video characters shift, that seemed to go away once buffer IC's were changed)

So it might be worth ensuring all socketed-IC's are making good contact / gently lifting & re-inserting these.
And might have to try some of the diagnostic EPROM's to see if they find anything, if still playing-up.

25th Apr 2021, 8:23 pm	#1752
ortek_service Octode Join Date: May 2018 Location: Northampton, Northamptonshire, UK. Posts: 1,441	Re: Non-working Commodore PET 3016 EDIT: Just saw your reply after I was typing the below. Had you removed UC7 before the fault happened by mistake? - As I thought UC5 (6522) was being being removed, to lift Pin14. However, I think the CASS SENSE switch reading may be involved, so there may be some other things to check (Possibly swapping-over the 6520's) --------- Is that with all pins of the 6522 inserted ? / Is there a chance the wrong one has been lifted? It seems the 6522's internal timers may be used by the Kernal for keyboard scan etc. periodic interrupts and could be some odd effects if not running correctly. Otherwise, it does seem it's mostly running OK some of the time, to get that far. And maybe an intermittent connection on an IC socket etc. somewhere (like with previous occasional video characters shift, that seemed to go away once buffer IC's were changed) So it might be worth ensuring all socketed-IC's are making good contact / gently lifting & re-inserting these. And might have to try some of the diagnostic EPROM's to see if they find anything, if still playing-up.