To see if I can isolate the cause of the XL1201 instability, I am going to physically inspect the two main cards with a loupe and flashlight. If I see anything suspect, I'll take a picture with a (cheap) USB microscope.
I am doing a detailed inspection of the solder side of the Merlin II CPU card first.
There are only two that are concerning to me, but several others were found. The two of most concern are:
- Seemingly bad solder joint or problematic solder joint
- Material in a empty socket hole - could it make shorts between the layers? Irrelevant?
Material in a hole of empty socket BB12
Bad-looking solder joint between CC25-26, DD-25-26
Black blemish near CD23
Poorly cut lead near EE25 but seems fine
FF11 - Slightly discolored joint
FF30 - Black stuff near solder joint, seems to be just a bit of fabric?