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Recapped Mac Classic ii Checkered Screen

DomDom

Member
I have a mac classic ii rev A and after a recap of the logic board still gets the checkered screen. I also have a working mac classic that I put the board into and still got the same pattern and I've been looking at the schematics and haven't found anything yet. Is there something I'm missing, a chip that goes bad, or what else can I do?
 

joshc

Well-known member
Can you post some photos of your logic board please? There could be cap goo under the Egret chip (U10) or around that area, because there are 4 caps there which all cause problems. Usually removing/cleaning it resolves this, but there can be other reasons for the checkerboard pattern.

1658895489932.png

Not the issue here but have you re-capped the analog board too? If not, that will be necessary for a Classic as they all have leaky capacitors by this point.
 

DomDom

Member
You are pictures of logic board and what the screen looks like.
 

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joshc

Well-known member
The board looks too dirty, there is lots of residue/goo around all over the place. This capacitor leakage residue causes shorts.

It needs to be scrubbed/washed with soapy water, then rinsed well with isopropyl alcohol 99%, and then left to dry thoroughly for several days.

Are you sure this has been recapped?

This capacitor doesn't look new, it has damage to the top:

1658923854353.png
 

LaPorta

Well-known member
In addition to the above, put your working Classic LB into the II, and see if it starts. Rule out any analog issues (though I doubt it with what others have pointed out.
 

bibilit

Well-known member
I agree with all that has been said. Capacitors have been replaced in my opinion, probably new, but yes cleaning the board is more important than having new caps.
Fluid is conductive and can easily make nasty things.
the Egret is contaminated, should be removed, cleaned and soldered back.
and yes, the AB board should have new caps as a minimum.
 

DomDom

Member
Okay thanks everyone for the information and I will start doing this and in a couple of days I will reply back with the results.
 
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