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Apple iie Platinum Garbled Screen Part 2

Im definitely not too familiar with the Apple II line, in fact I have an II+ that I will need help on getting to post. But this seems to be an issue with the Character Rom. I havent read the previous posting, but was the character ROM checked?
 
The character ROM is fine, the characters are wrong but are displayed perfectly.

Its clear that the CPU is getting bad instructions, since RAM has been ruled out. There are some other candidates that can cause that issue.
Check the +5v on the motherboard it should be between 5v and 5.25v but definitely not below 5v. Also check for AC ripple on the 5v line.
If the power looks good check/replace the sockets on the board, in your first post you mention some signs of corrosion on some of the chips.

I still think you should try the diag eprom I sent a link to, the results you get will narrow down the problem.
 
I measured the voltages, +5v is at 5.1v but +12v measures only 11.13v. The only other thing is, I'm not quite sure how to measure for ac ripple. Sorry.
 
To me, this just screams corrosion somewhere. I'd pull all the chips one by one, check for green fuzzies, and reinsert. I'd even go so far as to send the board through the dishwasher for good measure.

Did you check the power supply UNDER LOAD? It makes a difference with these units I've noticed.
 
masterpigeon said:
I measured the voltages, +5v is at 5.1v but +12v measures only 11.13v. The only other thing is, I'm not quite sure how to measure for ac ripple. Sorry.
Click to expand...

To measure for AC ripple with a digital multimeter just set the meter to the AC range and it will filter out the DC component.
11.13v is fine if there is no AC ripple on it, was the power supply under load at the time?
 
I checked the voltages on the board once more, 12v measures 11.53v and 5v is still 5v. I don't believe there is any ac ripple with either of them. (It measured 0.004acv)
 
Here is a picture of what the computer was doing after I reseated all the chips. it won't do anything else now, It only displays this screen. I also noticed something missing on the board while cleaning it.IMG_20180124_132105.jpgIMG_20180124_132503.jpg
 
Holy crap that pitting! :shock:
How much corrosion is going on all over that board?

Also CR2 is where an LED would normally sit. It is missing on your machine.
 
Here are some pictures of the board:

IMG_20180124_141049.jpgIMG_20180124_141056.jpgIMG_20180124_141102.jpgIMG_20180124_141110.jpg

Apparently, the guy I got it from stored it in a leaky shed for several years and it must have gotten soaked because when I first picked it up, heaps of rust fell out. My table is still covered in it. Most of the metal base was rusted and heavily pitted but the board sort of looked ok but apperantly not. So that is why the board looks the way it does.
 
well... There isn't much to lose at this point.

Get some dish soap, a brush with long stiff bristles, and some super hot water. Go nuts. Hopefully it helps. I personally use Dawn soap.
 
Well, soaking it didn't break it... nor did it fix it. It just changed it slightly.

IMG_20180124_163604.jpgIMG_20180124_163621.jpgIMG_20180124_164606.jpg
It will display the bars or thin bars and eventually change to the '@' screen.
 
Well, I would have let that dried longer... In all likelihood there is a broken (or shorted) connection somewhere. Or a bad chip maybe. You might try over at http://www.applefritter.com/ they are more specialized on these systems.
 
Are Platinums rare enough to warrant fixing this one?

Get some good contact cleaner, and burnish all the IC legs and socket pins. If that doesn't fix it, start replacing sockets. Surely this will fix it.
 
cleaning the pins helped quite a bit. I even got it to beep! With the keyboard disconnected, it will now display a checkerboard pattern and beep seven times every 15 seconds or so.

[video]https://photos.google.com/photo/AF1QipMz5NA35px15e8myKhd35qZ4Nk6wKbOekQB-sbs[/video]
 
Your link leads to a sign-in page.

I expect that all you have to do to get it fully functional is clean the pins and sockets even better.

If you have a multimeter, you can check the resistance between chip pins and the solder pads on the bottom of the board to see where you have bad connections.

By the way, it sounds as if it's doing the self-test, so it may already be fully functional minus the Apple keys. If you have the keyboard plugged in, verify that those keys are working. (You may have corrosion on the keyboard connection as well as inside the keyboard).
 
After seeing the photo's I'd be replacing the sockets for sure, even if its currently working when you plug the keyboard back in.

Those sockets will not be reliable, you are also going to have huge issues with plugin cards intermittently not working due to the corrosion on the slot connectors.
 
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