HP-65 Card Reader Problem Help

[PANAMATIK]

(06-08-2015 10:43 PM)Phoenix Rob Wrote:  Hello all,

I have been a viewing this site for many years but decided to join today! I have an HP-65 that has a card read/write problem. I replaced the gummy wheel and now the cards pass through without problems, but I cannot read or write. Can someone with experience in this area point to what I should check to fix this problem? Also, how critical is the card reader speed?

Thanks!

Rob

I'm not an expert. But as no expert seems to be here, I try to give an answer.

I replaced the gummy wheel too in my HP-67 and HP-97 this week and had the same problems. Reading sometimes works and sometimes not. Some of the standard pac cards are readable, other not and the same cards are sometimes readable and sometimes not. I assume that this unreliability depends on speed. The remaining friction of the gummy wheel material could be responsible for different speeds. But I don't know how sensible the card reader is against too low or too high speeds. Is 5 percent tolerable or not? What is the nominal speed? Does it depend on battery state. I don't know.

Unreliable read can also be caused by other reasons than speed, signal quality for example. Are the cards magnetic recordings still ok?

Next week I will try to do some experiments. I will measure the motor speed and I will drive the motor by an external regulated voltage to find the best motor speed for reading the cards. Then probably I can give more answers.

And I have a question too. Still I don't fully understand the 'clutch' problem. And I don't know if I have this problem in my calculators. If the "clutch" is faulty, does it cause only speed variations, or does it cause stopping the wheel? Any experts there?

Bernhard