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Apple II Plus Won't Boot
- Thread starter Joad
- Start date
Bad RAM or 7400 series chip for RAM Support (on the side by the RAM). I know you can test each bank one at a time with the bottom bank for 16K of RAM.
Also look at your ROMs. Gently remove them and put them back in. Corrosion on the chips' legs can also do this.
Also check the power on the PSU with a Multimeter. You should get +5V, -5V, +12V and -12V when connected to ground.
Also look at your ROMs. Gently remove them and put them back in. Corrosion on the chips' legs can also do this.
Also check the power on the PSU with a Multimeter. You should get +5V, -5V, +12V and -12V when connected to ground.
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Usually with II+ problems I start by prying up all the chips and reseating them. That gets through the oxidation and restores contact.
Joad, it looks an awful lot like this problem here (it's case one). I'd start by replacing the 74LS139 latch chip at location F2 and perhaps the one at E2, too. According to this, the 6502B processor could also be bad, or it could be a ROM problem, but I'd just start by checking 74LS139 - they're very cheap and easy to find enough that they're worth a shot.
It doesn't matter how clean the II+ is. The chips have a tendency to lose contact with the sockets over time. When they do, the only way to reliably restore contact is to lift up the chips and reseat them.
I have a couple dozen II+ in a box in my home. They all worked when I put them in a couple of years ago. I'm certain several will need the chips reseated by now
I have a couple dozen II+ in a box in my home. They all worked when I put them in a couple of years ago. I'm certain several will need the chips reseated by now
Just because it looks clean does not mean that it is. Where the pins on the chips rub against the socket is where things go bad and lifting the chip and re-seating it fixes it in 99% of the case. This is an area that you can not see with your eyes unless you have 20X magnification built-in.
Both WayneStewart and Sherry Haibera are right. Too bad you got rid of the machine, because part of the "fun" of the hobby is solving your own problems when so called certified experts can't. How many A+ and MSCE tech out there can figure this out? maybe 1 out of 250,000. If that. If given some work this could have been a successful machine. At least it got video!
You need to take your time with this and you need to figure out the basics. The Apple II Schematics and repair guides are online so you can get it.
Both WayneStewart and Sherry Haibera are right. Too bad you got rid of the machine, because part of the "fun" of the hobby is solving your own problems when so called certified experts can't. How many A+ and MSCE tech out there can figure this out? maybe 1 out of 250,000. If that. If given some work this could have been a successful machine. At least it got video!
You need to take your time with this and you need to figure out the basics. The Apple II Schematics and repair guides are online so you can get it.
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