HP card reader drive coupling

[Geoff Quickfall]

It is not a clutch! It was not supposed to run with a jammed card. Cards were not supposed to jam ;-) Strictly a couple. HP decided that a jammed card would not burn out the motor as the user is right there inserting the card and could turn the machine off.

Off course I have not tested this info!

Again anecdotal in conversation with HP designers of the 41C version.

Rinsing with IPA: I use a lab plastic wash bottle with nozzle and also IPA in a plastic spray bottle which produces a jet for those hard to get places. Also the IPA is excellent for removing the gummy residue if your pinch roller and couple decomposed the gummy way and not the hardened crumble way!

Cheers, Geoff

Example of extreme gummy wheel:



Motor assembly and couple; Label C is the original couple which in this exampled hardened and no longer gripped the motor shaft. This caused slippage as the card passed through the pinch roller. It is a good idea to repair both at the same time. Some have added a dab of cyanoacrylate glue (super glue) to the motor shaft and reinserted into the old hardened couple. I don’t what the long term efficacy of that solution is. So far all my repairs with the insulation method (15 HP41C readers, 12 HP 65 and 9 HP 67 readers) have not failed over the last 12 years. However they do not get a lot of use. I did check my versions and they all work perfectly:



Example of insulation method for couple with no glue; the inner red insulation is half the length of the outer white insulation and is inserted into the white insulation. This is due to the fact the worm gear shaft and the motor shaft are different diameters.



Completed assembly: