HP-92 printer problem (not the gear)

[Jonas Sandstedt]

Hello,

I ran into similar (but possibly not the same) problems a couple of years ago, see

https://www.hpmuseum.org/forum/thread-1613.html

Even if your problems are different, some valuable tips may be found here as well.

For me, finally it seemed as one of the quad transistor IC seemed faulty and I replaced the printer sub PCB which worked well. Later, I learned that these IC could be substituted with MPQ3904, but I have not investigated this further. If you have a working HP-97 you might try to switch sub-PCB. You need a flat tool to such as plastic or metal sheet that is cut into shape to remove the printhead flat cable, different tips are discussed in the forum. I use the protective metal sheet of an old 3.5 inch floppy disc that is cut into shape – a tip from Ignazio. It must be said, however, that working with electronics, in particular old electronics, is risky and may result in unexpected failures.

Finally I would again like to mention that a new HP-97 service manual is available at
https://literature.hpcalc.org/

Best regards
Jonas