Threaded Mode | Linear Mode

polbit · 11-16-2023, 12:17 AM

Just purchased a non-working HP 97 calculator. After removing the corroded battery pack, cleaning everything really well, and inserting a new battery, it came to life! My first LED HP, so it's been fun playing with it.

While the calculator looks mint, neither the card reader nor the printer work. I assumed they wouldn't, since those gears, etc. are mush. Sure enough, when I opened her up, the printer gear fell out in parts.

Now, on to the question. The motor keeps spinning constantly whenever I turn on the calculator. I disconnected the printer board by removing the positive cable from underneath and it's all quiet now. Any easy troubleshooting steps besides the obvious replacement of the moving parts? I'm assuming the motor should not be just spinning without accessing the printer?

teenix · (This post was last modified: 11-16-2023 12:57 AM by teenix.)

The PIK chip tries to home the print head if the home switch is open when the power is turned on to get it ready for printing. This may be because the power was removed before printing had finished, or after repairs, or faulty.

If the gears are broken, the carriage cannot move, but the PIK chip does not know that, so it keeps the motor running. As far as I know, there is no timeout mechanism.

If you manually wind the printer carriage home, (turn the larger black plastic gear), the home switch will operate and the PIK chip will be happy.

Place the printer switch into MAN mode and try not to use any of the printer functions like [Print X] etc.

cheers

Tony

Mike T. · 11-16-2023, 09:02 PM

(11-16-2023 12:17 AM)polbit Wrote: My first LED HP, so it's been fun playing with it.

That isn't a bad way to start!

I'm very jealous..

polbit · (This post was last modified: 11-17-2023 01:50 AM by polbit.)

(11-16-2023 12:52 AM)teenix Wrote: The PIK chip tries to home the print head if the home switch is open when the power is turned on to get it ready for printing. This may be because the power was removed before printing had finished, or after repairs, or faulty.

If the gears are broken, the carriage cannot move, but the PIK chip does not know that, so it keeps the motor running. As far as I know, there is no timeout mechanism.

If you manually wind the printer carriage home, (turn the larger black plastic gear), the home switch will operate and the PIK chip will be happy.

Place the printer switch into MAN mode and try not to use any of the printer functions like [Print X] etc.

cheers

Tony

Thanks, that worked! This is such a cool machine...