The Museum of HP Calculators
HP Forum Archive 10
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|HP-65 card reader|
Message #1 Posted by John Nelson on 9 Feb 2003, 11:57 a.m.
I have an HP-65 that, cosmetically is near mint, but the rightmost digit is always partially lit on a couple of segments and the card reader motor runs (but is loud & sqeaky) and does not read. It does not appear to be a gummy wheen problem. It's like it needs to be cleaned / lubricated. Anybody know how to effect repairs for such thing?
|Re: HP-65 card reader|
Message #2 Posted by David Smith on 10 Feb 2003, 6:10 p.m.,
in response to message #1 by John Nelson
The reader noise problems are most likely due to lack of lubrication. A reader that screams like a banshee is caused by the tip of the worm gear cam running against a steel ball thrust bearing. If the reader wheel has not been replaced it WILL need replacing. The head probably needs cleaning also. Finally a reader that writes but does not read is usually caused by a flakey small blue dipped tantalum usually located along the upper edge of the card reader board.
Ghost segments in the display are caused by sneak currents devloping in the display cathode driver chip... the one just below the right hand LEDs. The ghost-be-gone cure is to connect a 200 ohm resistor from the offending cathode line on the chip to the chip "ground"... the most righthand of the bottom row of pins. This chip actually runs on +8 and +4 volts... it does not connect to true gound. One has to be careful locating the resistor becuase of clearance problems with the molding of the case.
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