HP-65 reads but does not write


I recently opened up an HP-65 which had previously worked fine with a gummy wheel fix both reading and writing without errors. I opened the card reader to clean the card guides and small parts (balls and pinch roller) and also the keyboard. I reassembled, and everything works except it won't write cards properly. No errors, just garbage on the cards. I tried several blank cards to no avail. Any thoughts? Thanks.


got to make this short [wifi] on a bus in toronto.

first check wire connections to reader board.

next clean connectors to main circuit board and card reader board.

Then try rotating the pinch roller axle a few degrees as this will raise or lower the pinch roller and thus the card with reference to the reader.

then if that does not work the capacitor for the read may be deteriorating.

Search google hpmuseum hp65 card reader for explanation of electronics

hope this helps

cheers geoff


Tried everything to no avail. Now its even worse, won't read or write. I noticed a significant increase in motor noise. Would a bad cap affect the motor? Do all those flat contacts below the nylon balls have to make contact with something? Anyway, thanks for the help.


Look at the clutch betwen motor shaft and worm-gear. Perhaps this could be your problem, if it does not writhe/read the cards and you hear bad sounds from the reader.

Try again.




Actually, I think both the clutch and wheel were rebuilt previously by another owner, however the motor bearings were very dry so I relubed them. After re-assembly, it is now working properly and quietly again. The actual problem turned out to be a broken wire solder connection between the reader control board and the main LED/Keyboard. Thank you for your help.


Ignazio is correct:

typically the clutch is ignored when the pinch roller is replaced.

the noise is the clutch failing, as it is made of the same material as the roller.

oprn the case and remove the moter from it's housing via the two small screws. pull the clutch off and soak and clean with alcohol. Find a small diameter wire and remove the outer insulation.

the insulation should fit snugly into the clutch sleave. the motor spindle should fit into the hole in the insulation that carried the wire. this method alows the clutch to slip on a jammed card but provides enough friction to drive the card thru with minimal noise.

cheers geoff

I always replace the clutch at the same time as the roller as a new rollerwill stress the clutch.


Please see my reply to Ignazio, Thanks for your time and advice.


Postscript: I tried your clutch fix on another calculator, an HP-67, and it worked perfectly. This was a completely original clutch and when I pulled it off the motor shaft, the clutch material completely crumbled! I'm amazed that I found some wire insulation that fit perfectly. Again, thanks for your help.

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