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Hello everyone,
I need your help and advise.
I bought recently an HP 65 with a non operational card reader.
I have changed the gummy wheel , but I noticed that the colored wires (Blue, yellow,red,orange,blue) which connect the head to the circuits are not correctly welded.
I have only this HP 65 and I am not able to compare with another one.
However, I have some HP 67 and I noticed that the circuits are the same between the HP 67 and the HP 65 (i.e c-170 5-61).
As a consequence, could I consider that the "colored wires" have the same positions between the 2 calculators.
Many thanks for your help


There were several different versions the HP65 card reader circuit board. The wires were not all in the same positions.

The 65 and 67 readers are electrically much the same, even though they may use different chips (which are pin-compatible). The PCB layouts may be different.

What I would do is trace the connections from the reader head to the IC pins in your 67 using an ohmmeter. Now do the same tracing on the 65 reader board so you know what the 5 pads are and solder the wires down.

IIRC, black is an earthed screening connection

Red and Yellow are one head coil

Blue and Orange are the other coil

But you must get the polarity of the coils right too.

The HP65-Notes file in the articles forum here might give some useful info too.

Tony, David,

Many thanks for your help.


Hi again,

Is someone will be so kind to send me some pictures of the card reader for HP 65.
I understand from David and Tony, that there is different models.
Thank you for your help.