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Mac Classic Error Code Help

pj931

6502
Hi,

I posted a bit ago with some CRT issues and 5v/12v issues. Another Mac has been (mostly) liberated by changed TDA 4605, DP6, CP23 and the zener diodes around TDA4605.

Now I am getting the error code pictured. I understand it is a RAM bank failure in Bank B but I’m not sure what the 0400 in the bottom row means. I also don’t know which RAM chip is represented by Bank B. This error appears with or without the memory expansion installed. 
 

I have recapped both the analog and logic boards and any and all electrolytic leak was neutralized with vinegar then rinsed with IPA.

BDACFB59-5557-4E8C-8EED-532FAC78016E.jpeg

 
There are 1MB RAM on the logic board. One of these chips could be defect. 

The 400 means that bit 8 to 15 showed the error.

 
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