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Old 7th Feb 2020, 11:25 am   #14
John Earland
Hexode
 
Join Date: May 2013
Location: Middlesbrough, North Yorkshire, UK.
Posts: 442
Default Re: Commodore PET 3016

Quote:
Originally Posted by SiriusHardware View Post
Just found a nice PET repair video by the 8-bit guy here:-

https://www.youtube.com/watch?v=uHbhH7ISL_Y

The section at 2:42 onwards is of particular interest to you because it has a nice explanation / animation showing how the keyboard is scanned, and the various methods he uses to narrow down the fault.

Although his fault is different (no keys working at all) the diagnostic process still applies. At the moment my money is mainly on the 74LS145 decoder being faulty on yours since you've already changed the 6520.
Thanks for this. I would tend to agree with you. these are soldered in and I am a bit nervous about taking these out. I tried to do this once on an old Roberts radio and ended up frying the circuit board!!!
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