I got a pretty nice HP41C incl. a Card reader. I repaired the card reader (I used thermo shrink hose to create a rubber wheel instead of O-Rings), and now the reader works perfect - almost. When i try to store a program, it shows "PROTECTED" on the Display. So i analysed and found that mit must have something to do with the Optical circuit which detects wether the cards are clipped or not (I know about setting flag 14, but that's not what i want). To understand more: Which one is the LED? Which one is the Photosensor? Does the LED emit visible light or invisible?
Any ideas?
Thank you in advance,
Andy.