Mac IIx intermittent RAM issues

[tattar8]

I'm having trouble with RAM being intermittent.  The machine currently has 8 sticks of 1MB each installed.  The problem, however, is that about half the time, it only detects 4MB of RAM.  If I remove the upper bank, it still only detects 4MB, which leads me to believe the problem is in the upper bank.  If it does detect 8MB at powerup, the system is often unstable, and will likely freeze; after rebooting it, the machine is back to detecting 4MB of RAM.

I'm assuming this is some intermittent connection on the logic board, where should I look?  It was already recapped and washed, so no chance of cap goo being present now, but at that time I had to do extensive broken trace bypassing to get it running again since there was a lot of damage.

 

[Unknown_K]

Bad trace in the memory area I would think.

 

[tattar8]

Alright thanks, looks like I'll have to probe all the lines.  Do you know how the memory probe works?  Does it just walk through the addresses until it can't write anymore, and then decide that that's the top of memory?

Also, does anyone know of any memory test software that performs its own probe and doesn't depend on what was detected at startup?

 

[tattar8]

Update:  I hit every pin in each slot in Bank B with a logic probe.  There seems to be data going through each pin -- none of them seem to be stuck at 0 or 1.  What else should I check?