Mac Classic Checkerboard

[happy_Mac]

Hello, My Macintosh shows a chess board despite recap and a new EPROM. I also cleaned the board. But when I take out the RAM expansion, the Mac shows valuable lines.

Can anyone help me further?

 

[3lectr1c]

First thing you should do is check the voltages off the hard drive molex connector. Put a multimeter in the first and 3rd pin and then the 2nd and 4th pin, these will be your 5 and 12v rails, not sure which is which. If they're too low or too high, you've got analog board issues.

 

[happy_Mac]

The Analog board isnt the Problem, it just work fine

 

[3lectr1c]

You’ve verified it works with the correct voltages and another logic board? If so, broken trace near the RAM would be my next guess.

 

[happy_Mac]

thx, but it doesn´t help me.

 

[Paralel]

I take it you've already washed the board, then done a 99% IPA wash down to make sure there isn't any gunk left anywhere?

Assuming that, I'm guessing by your first post you meant "video lines" which would be a good indication that the RAM on the logic board is the source of the problem in some manner, broken trace, bad chip, etc...