Apple III garbage on screen at startup

[wottle]

I just picked up an Apple III locally and it came with a ProFile 5MB Drive (unfortunately no Profile card in the machine), two Apple /// Monitors, and the external floppy drive. I need to replace the RIFA caps as the big ones are cracked significantly.

However, I decided to start it up in the garage to get an idea of if it could boot. I know nothing about the III, other than that they were short lived and had thermal issues. When I started it up, the good news is I do get a picture out and the display on the /// Monitor looks pretty good. (The other /// Monitor has a tear in the anti-glare screen, so I need to disassemble it and remove. the screen). Unfortunately, the screen displays two screens of gibberish.

First, this, with a square in the bottom right that is changing:

Then I get a second screen that looks like this:

The screen goes black and then it repeats. I didn't let it go too long, because the RIFA caps looked like this (Yes, it appears there is a hole in one of them):

The remind me of the Apple II when it has memory chip issues. So, I decided to remove the RAM card, give everything a nice wipe down, remove every RAM chip, spray some DeOxit on the sockets, and reinsert them in a different order. I also removed and put DeOxit on the CPU socket. Unfortunately, the same result.

While I wait for my caps for the PSU, any thoughts on where I can start troubleshooting / ordering some replacement chips. Is it possible the CPU is bad? Is the 6502 available to buy if it was?

 

[wottle]

Just a quick update that may give some more idea of what's happening: when I do a Open Apple-Control-Reset, the screen resets and it appears the floppy doesn't try to reload, but the interesting thing is when I start typing on the keyboard, I do see the pattern change, which makes me believe some boot up is happening, but maybe the video circuit is bad. Not sure if that helps, but any advice would be appreciated!

 

[wottle]

OK, so I decided the RIFA caps are probably not in good shape to continue using. I removed them and tested and the .22uF one appears to be shot. Would that cause issue with the PSU voltage that could cause problems with the video output. I suspect the square in the bottom right that is changing is actually the RAM test showing possibly a bunch of bad RAM chips, but the video output is rotated or flipped.

Also, I removed, applied DeOxit, and reseated every socketed chip (and cleaned up a few of the chips that had oxidation or corrosion on the legs (surprisingly not many). Still the same result. Will likely wait until I can get the PSU recapped with new RIFAs and some of the caps (I got a kit from Joes Computer Museum). In the meantime, anyone have an idea why the video is corrupted like it is?

Also, is there a good way to monitor the voltages under load when the machine is running (like the floppy port on classic Macs)?

 

[ClassicHasClass]

I don't have much insight here for you but my Apple III did something similar and I put it in storage to ponder how to fix it. I don't remember the caps looking as bad as that but I'll check them again next time I'm in that unit.

 

[wottle]

It seems like Joe's Computer Museum is trying to specialize in the III. I ordered a cap kit, but I'm wondering if I should have added a video ROM to my order in case that is the source of my video problems.

 

[ClassicHasClass]

The video ROM might help, since you don't have anything recognizeable as characters in those pictures (the A3 should come up in text mode). Mine had properly formed characters; the screen was just garbage.