I have powered up the LA36 with the Selenar Graphics board in it, and
from the information kindly obtained by list members
article about the Selenar Graphics II), I have been able to verify
the unit indeed works. The graphics mode works, and all of the other
features documented in the Byte article seem to function properly.
The issue that I've found is that only 5 of the 7 print pins are
working. Numbered with the top pin as number 1, it is the 3rd and 6th
pins that are either not firing at all, or are jammed such that they
can't come forward enough to make an impression.
I can't find a service manual for this unit online anywhere, so I'm
wondering what the best approach to diagnosis would be. I do have
schematics, but since the unit has a Selenar Graphics II logic board,
I'm not sure how well the schematics will help. Since the Selenar board
replaces the stock logic board, I can safely assume that it retains the
pinouts for the connectors that go from it to the power board that has
the drivers for the solenoids in the printhead. So, I can probably
scope out the drivers to see if they are firing on pin 3 and 6 when
printing characters that require those dots, which I will do when I have
time, but I'm wondering the next step would be if I find that there are
firing pulses coming out of the pin drivers for pin 3 and pin 6.
Obviously, if I find that the pulses aren't being generated, then I have
to dig into the solenoid drivers for these pins and figure out what has
failed and fix it.
If I find that the solenoid drivers are OK, then what should be done
Would it be to remove the printhead and do what Tony suggested, which
would be to use a bench power supply (I have a good Tektronix bench
supply does truly does deliver 0.00V) to try to fire the solenoids to
see if they are gummed up? If so, how do I go about removing the
printhead to do this? Just from looking at things, it looks like I would
have to do a lot of disassembly to get the printhead out of there. Does
the printhead come off separately from the carriage that it rides on, or
do I have to remove the whole carriage assembly?
Any guidance would be most appreciated.