Hi. Another Apple ][+, a new-to-me problem that I am hoping some of you can point me to a solution.
The computer boots, beeps, and displays Apple ][ and the ] prompt. (No disk controller installed, 48K plus a 32K Saturn RAM card in slot 0).
However the display of the Apple ][ and the prompt are repeated. Here's a picture:
And if I type a little program ...
And try to run it...
You will see that the output, and the list of the program, have changed some characters.
What should I be looking to replace?
Looks like a video counter or vsync issue.
Check the 74LS161's (D11-14), A12, B11, B13, B14, C13 and C14 .
Thanks David_M. I tried all those chips, plus a few more that seemed part of the video path as well. Not resolved. All of them worked in a donor system as well.
I am going to try replacing the capacitor at C16.... just reaching for straws at this point. I don't have an ESR tester or anything, but I have ordered some replacements off of ebay for a few bucks. I'll report back. Always appreciate folks giving me advice and tips to try, so thanks!