Missile command PCB repair

KazooBR

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Donor 3 years: 2023-2025
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I need some suggestions, this one is strange to me.

Test mode indicates bad ram 3 and 8, sometimes also chip 7. These have been socketed, I swap them with rams from a working board and get the same errors.

Fluke cannot consistently get through a RAM SHORT test. I took note of these errors: At address 0000, bits 0,1,2,3,4,5,7,8,9. At address 0002, bits 0,2,3,5,7,8. At address 0003, bits 2,3,4,7,8. I also noticed the fluke giving an occasional timeout very briefly if I looped the test.

But - I CAN use read and write commands on the addresses the automated test flags as bad. So, would I have a contention issue on the bus because the automated test is busier/faster?

How do I troubleshoot that?

I thought I was all good after finding this broken resistor. That cleared the R/W ERROR but left me with these RAM DCD errors. 😞
 

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Barring any other ideas, I'll remove the sockets to see if they weren't installed well.
 
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