Apple III video issues

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Apple III video issues

hello i just joined this forum in hopes to get my apple III working again.

 

i have what i believe to be the mem diag screen. however it takes up the entire screen and is mostly random garbage. 

however if i remove the ram board completely i get a solid white screen.

 

i have tried reseating all the chips on the motherboard. and i swapped around ram chips to see if i could atleast get it to display a normal mem test. nothing i did changed it.

the on light on the keyboard is also working.

 

does anyone know where i should start looking? 

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Last seen: 2 months 1 week ago
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update. this still exibits

update. this still exibits the same issue with the processor and rom removed

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Joined: Jul 31 2014 - 17:48
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check memory

A good thing to do is to check the ram chips to make sure these are working. If its a 5v ram board (4164's), then maybe try them in a IIe to verify they are working ok.

/Rob

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unfortunatly its the 12v

unfortunatly its the 12v model. i have swapped chips around and nothing changed. what i have noted if i turn it off and back on the screen changes it pattern but if i reset it with the keyboard the patter remains the same.

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ahh, ok. That makes it a

ahh, ok. That makes it a little harder. Can you share a photo of your memory board?

 

It looks like the first row can be either 32k or 16k drams and I think also the second row can be either 32k drams with the 3rd row empty, or second and third rows can be 16k drams. So maybe you can remove the 32k rams and replace with 16k rams from a known good source for testing (AppleII+). You just need to be careful to insert the 4116's in the correct position in the socket as they have two less pins than the 32k rams. Have a google for 'apple iii 12v memory board' and have a look at the images to see this.

 

3 rows of 16k drams will yield a 96k Apple///. Not sure you can do much with that, but it should at least run the monitor rom ok.

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