Found these inside a non-working 71B

[MikeSD]

Thanks. i'll look at schematics.

Turns out it's a little more complicated than I thought. I still think the problem is a connection. But it fluctuates between 4K and 2k, missing. And the exact numbers seem odd. i removed the 64k since those are reportin gòod.

The only RAM chip I soldered to is the top chip on other side of board. The only thing that makes sense is if one of the nibble lines is open, to cause it to toggle betseen the two values.

oh well, on to tomorrow.

thanks for schematic. much better than my copy

Update: When I have a problem, I just can't let it go. The only thing that made sense was my unsoldering the 64k RAM from the 4K RAM chip. So, I reflowed the solder on that chip and now its working again. Only FORTH to go, then final button down and test.