Hp-41C card reader - dead

[David Hayden]

This is the hardest part of the repair. The piece you're looking at is a dampening couple. It's a cylinder with one outer diameter that the metal sleeve slips over. But the inner diameter on one end slips over the motor axle and a different inner diameter on the other side fits over the end of the worm gear.

To create this, I used two different cylindrical materials: one that had the wider diameter to fit over the worm gear and one with the narrow diameter. I pulled the narrow piece into the wider piece. It took a while but I eventually settled on wire insulation for the inner piece and shrink wrap for the outer piece. The trick was hitting the combination with just enough heat to shrink it to the right size.

Other posts have pointed out that shrink wrap can be perilous here. If you shrink it down too much, it gets hard, which defeats the purpose of the dampening couple.

Good luck. Have patience.