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Macintosh 128k Video Problem

MacAttack

MacAttack

6502
Hello, I recently bought a 128k Mac (non-functioning) and the seller told me that he thought that the 74F253 Ram Multiplexers were bad. But after replacing them with new Motorola ones, the screen still has the same issue. Here is a photo:IMG_1379.jpg

I have no idea where to got from this point and a google search came up inconclusive. Please Help!!

 
Did you swap just the ROMS or the entire board. I would have swapped the board, a lot easier and would rule out bad RAM.

 
The ram has been socketed and replaced so I ruled that out and the Mac plus board is not compatible with the 128k case

 
You yourself socketed and replace the RAM?

Does not matter about board fit, its compatible for testing. You dont have to put the rear bucket on.

 
Last edited by a moderator:
No, not myself so I guess it could be bad ram, but I'm just going off what the seller said. Anyways, I will test the Mac Plus board in it too.

 
If the ROM is good, and the RAM is good, then one of the GALs/PALs could be at fault. 

OR there is the rare possibility that this mac had a memory upgrade and someone removed it trying to get it original but didnt undo the mods required to the board. 

 
Last edited by a moderator:
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