I recently inherited an Apple II+ (RFI rev), and it seems to boot fine, but it has some serious vertical lines on the video output. I've been troubleshooting to the best of my ability, and have had no luck whatsoever getting it to work.
Things I've done so far:
- Replaced UA3, UA9, UB2, UB10
- Verified correct frequency and voltages on 14MHz, 7MHz and LD194 clocks
- Verified power and ground connections to the above chips
- Verified continuity between relevant UA3 pins and the character ROM
- Tried all 3 rows of RAM in the boot row to verify no chips are bad
- Resocketed processor and all 6 D/E/F ROMs
- Tried adjusting video and color trim pots
I'm at my wit's end with this, if anyone has any idea what could be causing it I'd really appreciate the input. I've attached pictures of the board and video output to this post; the video starts out like the first picture with the bars made of dots, but they transition to being solid within a second or two of being booted up, faster if it has been on for a while and only just restarted. Certain keypresses do work so I do believe it's booting up ok, just seems to be an error somewhere in the video circuit.
Go to BASIC and try typing the
HGRcommands. If the video fault suddenly becomes confined to the bottom 4 lines of text (eg: the text window) then it would suggest the fault is in UB2 or something before it, possibly the 2316B "ROM SPCL" at UA5.
Of course the graphics window might exhibit the same fault as the text area...or it might show some totally different fault. It's worth running the test to find out -- each graphics mode exercises different circuits in a different way.
EDIT: I suggest trying all four screen commands, and noting how each behaves in turn: GR, HGR, HGR2, and TEXT.
(If you don't have the ability to type keyboard commands, then do you have another Apple ][ with a disk drive that could be borrowed?)
Thanks for the input! Went ahead and tried all of those commands, pictures of what I got are below. Going to TEXT from any of the other 3 states produces the flashing seen in the video, GR and HGR give the bottom few lines bars and nothing else, and HGR2 produces the full-screen thinner vertical bars. Given that I've already replaced UB2, I doubt the problem lies there, so would you recommend switching UA5 as the next step?
Wow, there's so much unexpected data in that video that it's hard to unpack it all -- it's hard to guess if there's one complicated fault vs two simple faults that interact to produce complicated-looking effects.
Cataloging some details:
There might be faults in those gates at UB11 or UB13, but UA5 just keeps arising as a likely suspect. This could be a good excuse to upgrade your original character ROM to a lowercase one. Reactive Micro has replacement firmware ROMs for $10 apiece, so you could choose an original-style "II+ 7341-0036 Character Generator" or an enhanced "II+ Lowercase Generator". Either of those choices could replace the original 341-0036 in socket UA5.
I actually forgot to mention that I already swapped UB11 and UB13 with identical chips from elsewhere on the board to see if the issue would resolve itself (it did not), so all signs seem to point to UA5. Just ordered a new one, I'll be sure to report results once it arrives in a few days!
Why don't you try running the Apple II RAM Test Utility? I think you will be able to see and read the results on the monitor just fine, before the machine has a chance to heat up.