HP-41 Card Reader 82104A repair questions

[PeterP]

Quote:Oh! And what is the function of the internal LED? I don't see a corresponding photo-detector.

You can find the Cardreader Repair manual at TOS where they discuss on page 3-6 the repair of the phototransistor. Earlier on they describe the various circuits and their functions. I believe it is used to detect a card being entered, but others might have better information.

hth.