HP 75

[Garth Wilson]

I hope this is ok since the topic has migrated.

My Thinkjet no longer prints. It acts like the cartridge is dead, but all cartridges act the same. Absolutely no printing at all, even right after priming the cartridge and cleaning the contacts. The printer goes through the motions, but the paper stays totally white. Are there any easy things to look for? It's not much of an issue, because I go through other interfaces to print with parallel dot-matrix impact printers.

As for the battery in the Thinkjet, mine went bad in the late 1980's. When I found out how much a new one cost, I first replaced it with a 9V battery. That worked as long as the battery was brand new; but after about six pages, the battery could no longer deliver enough peak current for the job. I probably could have just put it in the battery box along with a big capacitor and gotten away with it. What I did instead was to make a 7.8V regulated power supply, which cost me fifty cents. I had everything I needed to make it except one zener diode, and the diode was fifty cents.

I never bought the disc drive, but my tape drive still works like new, as do my tapes, using an external regulated power supply since its batteries are long dead too; but I have a lot of memory in my 71 and 41 so I seldom need to get the drive out.

Someone gave me a beat-up but working 75, but I have never used it. It has no battery pack, so I clipped an external regulated power supply onto the terminals to chek it out.