I have a problem with the Apple II+ motherboard(RFI) which I restored and had been working well without problems so far. The problem occurred yesterday.
The symptom was that the HGR mode became unstable and the screen was slightly flickering. I summarize the symptoms after restart. With reference to previous posts
, I inspected the IC pins and replaced , but it is not improved. I can not identify the problem IC. Character ROM may be suspicious, but this can not be inspected because it does not have.
- No texts, but colored squares are displayed at the position of letters.
- 24 horizontal bars are displayed on the screen.
- Keyboard inputs are not visible, but commands are accepted.
- Can call GR mode, but not HGR/HGR2 mode.
I attached screen shot at startup. You can see the apple ii logo, the prompt and the cursor at the top of the screen. When I type something, a square appears instead of a letter.
I will be very thankful for getting advice on solving the problem.