RetroGadgetMan
Experienced Member
It didn't occur to me that there may be modern equivalents. Fingers crossed I will get my post this Saturday. It's going to be like Christmas morning due to the build up
Great progress !Yep, that looks like either a faulty character generator or possibly the video shift register or something driving the character generator.
Is the character generator IC in a socket? If so, we can remove it and stimulate the data outputs.
You always appear to have the left-hand side pixel of each character cell set. This might be the data bit to check to see if this is toggling from the character generator (indicating a shift register fault) or not.
Of course, we coukd have two (2) independent faults concurrently...
it is strange that we either have completely solid blocks or completely blank blocks though.
Also, you should be able to monitor the address line inputs to see if they are all toggling away.
Perhaps a Saturday afternoon looking at the address lines to, and the data lines from, the character generator with your oscilloscope to see what you have?
Dave
I don't want a lot for ChristmasAll I want for Christmas is a working PET !
There could be a song there somewhere...
Dave
I guess I kind of expected it.Bummer...
But not wholly unexpected either I am afraid...
Dave
I think Pin 2 of C5 must be ok in both its frequency & duty cycle, or there would be no horizontal line on the VDU.OK so nothing much happening... back to basics...
Do you still have HSYNC?
What's happening at pin 2 pf C5?
C5 pin 2 hi lo pulseOK so nothing much happening... back to basics...
Do you still have HSYNC?
What's happening at pin 2 pf C5?