HP 46 repair

[AndiGer]

@Vassilis: Wish you success when replacing U8. Diidn't know you still can get those old chips. Maybe used from a donor machine only?

Yesterday received a Casio R-1 calculator that also has the Shinshu Seiki EP102 inside. 3 teeth from the 17/68 double gear are missing but still printing.

Removed it from the R-1 and connected to the HP-46. As expected the printer also works inside the HP-46. But of course the characters on the print drum are different.

So one step could be to interchange the print drum between those two printers. No easy step ... (and steal the double gear from the other printer).

The printer from the R-1 is a different design. I attached images of the R-1 printer. Motor side and electronics are different design, right side drum gear is pure metal with a marking hole instead of plastic-metal mix with a marker in the plastic.
The design of that one coming from the HP-46 is identically to that in the link in post #17.
Hoped I could compare the two printers directly.

I measured the resistance when detached from the calculator between red and black wires:
The one coming from the HP-46 measures 1,300 Ohms continuously.
The other from the R-1 starts at nearly infinity and drops to 480 kOhms. When I turn the motor manually resistance rises to infinity to come back after some seconds to 480 kOhms.

What can I look after in the original HP-46 printer's electronics? Still hope I can get it back running ...

One possibility: Cut the leg of the 22 uF 10 V capacitor and measure that one? If ok I could reconnect soldering a short piece of wire?