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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.thumb.jpg.365241eda5b122a9c4308a9410be89cc.jpg

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

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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. 

Edited by techknight
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