HP 65 card reader problem



#2

Hello,

this is my first posting here, but I know HP calculators since 1973 and use them since 1975.

Recently I came across a HP 65 in unknown condition. According to the vendor, it had been used for surveying in the middle east, and yes, it was full of dust and dirt, and everything is quite worn out. The number keys don't click any more, as the springs have become soft.

But, after a lot of cleaning and replacement of the keyboard plastic foil, the card reader rubber wheel and the battery cells, it works nicely again. Since a long time, I wanted to see this LED display!

However, I can't get the card reader to work. All parts are clean and in the places where they should be, the motor and the wheel work when I apply external voltage, the switches operated by the nylon balls look o.k. and the contacts are clean. When I insert a card, I can hear the "click" of the switches, but the motor just doesn't start.

Any idea what I could try next?

Thanks, Helmut


#3

Have you checked continuity between the card reader board and the main pcb? The contact balls make contact on the keyboard pcb and pass the sgnal through the 6-8 spring contacts. I found I've had to make sure these are clean and widened them out again (to get good insertion force) to make some readers work again. I must admit that this cured reading problems (error) as opposed to not starting.

Did you clean the contacts on the keyboard pcb? A red pencil eraser works great.

Also, if need be, adjust the leaf contacts so the are level with the plastic.


#4

Also, make sure the keyboard PBC has good pressure on the card reader switches, which is often only possible by screwing it all back into the case.

Cheers,
John

#5

Quote:
Have you checked continuity between the card reader board and the main pcb? The contact balls make contact on the keyboard pcb and pass the sgnal through the 6-8 spring contacts. I found I've had to make sure these are clean and widened them out again (to get good insertion force) to make some readers work again. I must admit that this cured reading problems (error) as opposed to not starting.

Did you clean the contacts on the keyboard pcb? A red pencil eraser works great.

Also, if need be, adjust the leaf contacts so the are level with the plastic.


Your last suggestion brought the (partial) solution: the fifth contact (the one which is not operated by one of the four balls), apparently the one which feeds the signal back to the keyboard pcb, did not make contact. After bending it a little bit more outwards, the reader now pulls the card through! However, it makes a loud, squealing noise and the transport speed is not constant, probably because of the latter the display flashes after reading a card.

I found some hints here in the forum archive concerning the noise, and the speed issue is most probably due to the rather crude, hand-made rubber wheel replacement. To be continued ...

Cheers, Helmut


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