Congratulations on getting the Commodore 64 fixed! Sometimes it works out where the fix is as mysterious as the issue. Your technique was methodical and eventually worked! Great job and great video!
Very well done Ken. Sometimes stuff just stops working and we don't know why, makes sense that the opposite should happen from time to time :) My moneys on what you said, something very small that you somehow "fixed" while replacing the resistors. In any case that's one more system you can chalk down as a CRT success story.
@@CanadianRetroThingsI can’t tell you how many times I have repaired machines that just “magically” started working, especially when I turned the lights off and returned to the task in the morning and it just worked. Ours is not to ask why but to move on to the next machine. Otherwise you will go crazy.
Hi Ken, great you didn’t give up on the good ol 64! I‘m by no means an expert on the breadbin or fixing vintage computers but let me give some tips what you could check to make sure it works reliably now. Given that the symptoms mostly disappeared after you replaced those resistors even by the same values made me think of cold solder joints or one / some very marginal chips. The cold solder joints would be the obvious one but the reason may not. I think one of those (maybe more than one) was a pull up (or down) resistor. Those old TTL logic ICs needed much stronger pull-ups than todays CMOS logic. So if there were cold solder joints then the resistance was much higher than it had to be resulting in a weaker pull up. Sometimes even a couple 10 ohms can make a difference which is well within the tolerance of those 1/8W carbon resistors and could also make that it was not working. So a weak pull up can cause a weak signal from an marginal IC to have a much slower rise time which can cause a timing issue - especially when timing was created by an RC network which there are a couple of as some kind of in production hot-fix. In such a case the old capacitor can also become an issue if its value isn’t what it once was. These kinds of problems are very hard to diagnose and normally require good understanding of the circuit, its components and the timing requirements OR loooots of patience 😅 so GOOD JOB being a bit lucky.
Oh wow, I sure do wish that rendition of The Teddy Bears' Picnic resolved instead of leaving us hanging like that 😬 that's even worse than leaving Shave and a Haircut unfinished!
@@CanadianRetroThings I genuinely had to go “…nic” after a couple of seconds for my sanity hahah. It might’ve been a basic attempt at looping by the programmers, since the “if” at the start of the song is the same note. But dang! Most loops programmed like that have a different segment to end with, when it’s not going to loop, while this one just stopped cold.
Ken, did you check your board with a different PLA? Sometimes the new pla’s have some small compatibility issues. Someone else has done a video about issues with the new fga or gal PLAs. Another option is a cold soldered joint. Reflowing the board may have fixed it
