HP65 card reader problem



#7

When I insert a card in my 65 card reader, the motor does not turn on. I have tested the motor spins OK with 3V, what I suspect is wrong is the gold "fingers" are not bending enough to make contact with the PCB. Can anyone explain exactly how all of the fingers work ?, and can anyone suggest how I can test proper operation of them ?

I also dissmantled the card reader, replace the gooey roller with two O rings, and cleaned everything with Electrolube Ultrasolve circuit board cleaner, and reassembled it. But still no motor activity when I insert a card.

Thanks - John


#8

Hi John,
With the HP-65 back removed, remove the main cpu board. Next, hook an ohm meter between pins (counting from the right to left, pins at the bottom) 9 and 14. The reading should be infinite. Now insert a mag. card into the reader until you just feel it engage the first nylon ball/spring. The gold finger switch should now connect the two pins. If they don't then you will need to remove the keyboard pcb. Find the gold fingers and tighten (turn clockwise) the small adjustment screw on the second finger from the top. SThere are two screws on this finger. Tighten the one to the left (top pointing up). Start maybe with 1/4 turn and try the connection test again. Repeat until the switch works. Sometimes the switch does not work because there is a wire sandwiched between the keyboard pcb and the battery back.Then the switch has to bend a lot farther in order to work. If the switch is working and the motor still does not turn on, then there is a bad connection somewhere else. Usually it is where the wires connect to the card reader pcb or motor to card reader wires.
Hope this helps.
Erik


#9

Thanks Erik, I'll try that test.

#10

John,

All of what Erik says is the right thing to do first. But in really bad cases you might have to bend the fingers directly. I use fine needle nose pliers and bend the contact very, very slightly between the adjustment screw and the roller ball. It's sort of a trial and error approach, but if you hold the bottom of the card reader at eye level you want to get the tips of the contacts almost flush with the surface plastic as it touches the circuit board. (It's really not that hard to do with practice, just be very gentle with the pliers.) After that you can use the adjustment screws to refine your work, if needed.

-Katie

#11

I have had two calculators where I needed to adjust the fingers. I visually determined which ones need to be adjusted.

You do this by disassembling the calculator. Remove the CPU circuit board from the center sandwich. You should then be able lift the keyboard Printed Circiut Board (PCB) from the plastic middle part.

When no cards are inserted into the slot all four of the long fingers are retracted back into the shallow recess. As the card goes progressively further into the slot, all four of the fingers reaches up sequentially to contact the bottom side of the keyboard PCB.

To determine which one needs to be adjusted hold the plastic center so that you can just sight along the top edge without seeing into the recess (you are looking across the top of it). Have the top edge of the calculator to your right.

As you put the card in it will hit the first small plastic ball which pushes up the motor run finger. You must see this finger come up out of the recess to where it would contact the bottom side of the keyboard PCB (if it were all put together). If this finger (I believe that it is the closest one to the top edge) doesn't come out of the recess, then that is why your motor isn't running. If it does come out, then the problem is elsewhere.

As the card is pushed completely through by finger pressure you should see all four of the fingers come up. In the order that they come up they do the following things: 1) start the motor, 2) tells the calculator that the card is up to speed and starts the read/write circuitry (depending on the WPRGM/RUM switch position), 3) senses the leading edge of the card and polls the fourth switch which, 4) senses whether the corner of the card has been cut off for write protection.

My first HP-65 had a problem where it either wouldn't read or write cards. I had blank cards but no pre-recorded ones so I could tell which problem it was. A kind gentleman sent me a card with a program already on it. That read OK so I knew it was a "write" problem. Upon doing the above procedure I found out that the third finger wasn't coming out of the recess. Hence since it never saw the leading edge of the card it never polled for the cut off corner. Without a "I'm not cutoff reply" from the fourth switch the calculator didn't write to the cards. It has worked like a champ ever since I adjusted this switch.

Remember, if the finger doesn't come out of the recess it could have two causes. First would be that the finger needs adjustment. Second could be that the little plastic ball that the card pushed up is gone. If this is the case, no amount of adjusting the finger will help.

There is a good article on this website about the card reader design < http://www.hpmuseum.org/journals/65crd.htm>. There is also a picture of the fingers <http://www.hpmuseum.org/65crdrbk.jp>. These should give you a better understanding.

Hope this helped. I just bought a scanner and have an HP-67 that needs repair, so maybe I'll be able to document this in the future.

Matt Riehl


#12

Hi Guys,

It turns out just to be dirty contacts, on the PCB in particular. Now the motor turns on OK, but the feed speed is uneven. Maybe my new "O" ring roller is not quite right. Thanks for all the suggestions and help. Cheers.


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