Easiest
starting point is to check operating voltages. If during
printing they drop or go flakey it's the PS. The fact that it
prints at all says most of the logic is solid and working.
Allison
One of the reasons I want some kind of schematic.
So I can know what voltage levels should be where, and if I find
There pretty much has to be a +5V line for the TTL, microprocessor, etc.
You can find that from data sheets on some of the ICs. I'd start by
checking the voltage between that and logic ground (found on the gnd pin
of similar ICs).
-tony