This shows the final parts. The cylinder which holds the ball point cartridge is magnetically raised. It is lowered by the spring in the top assembly. The original part has very little clearance in the pen body which has the electromagnet coil. The new part has somewhat more play which probably reduced the flux coupling so it didn't pick up. A steel washer was glued to the end to allow it to operate. It reduces the pickup distance but still has sufficient movement to raise the pen off the paper. This also shows the top assembled with the spring and brass washer ( 49K) inside and the larger steel washer glued in to hold the other parts in place. A replacement pen cartridge has been cut down to fit. The cartridge needs to have the small diameter tip which used to be common but most new pens have switched to larger diameter tips which don't fit.
Feel free to contact me, David Gesswein email@example.com with any questions, comments on the web site, or if you have related equipment, documentation, software etc. you are willing to part with. I am interested in anything PDP-8 related, computers, peripherals used with them, DEC or third party, or documentation.
PDP-8 Home Page  PDP-8 Site Map  PDP-8 Site Search