banman wrote: ↑Sat Jul 16, 2022 1:58 am Hi rmzalbar,
Correct!
I found this Sparkfun article on TTL logic levels
https://learn.sparkfun.com/tutorials/logic-levels/all
These C64 boards are very old. Traces and cold solder joints can be problematic in my limited experience.
I managed to take some more observations of my working 250425 C64 mainboard.
I looked at CPU pins 7, 8, 9, 10, 11, 12, 13, 14, 15 then 32 and 37. I did notice that these logic signals on dpalmeira's 250425 C64 mainboard looked unusual.
One will see that CPU pin 37 looks rough. Maybe, as rmzalbar suggests this is acceptable. These signals have been taken from a normal working 250425 C64 mainboard with the SID chip socket unpopulated.
Maybe we need to look more carefully at some of the Logic signals going into and out from the other support logic IC's on the mainboard.
Many apologies!
Something has happened here and some of my observations have disappeared.
Hopefully the signals at CPU pins 7, 8, 9, 10, 11, 12, 13, 14, 15 then 32 and 37 can be seen.
I did notice that these logic signals on dpalmeira's 250425 C64 mainboard looked unusual.
Not sure why this happened..