|Re: HP-67 Card reader woes|
Message #2 Posted by Tony Duell on 20 Sept 2005, 6:14 a.m.,
in response to message #1 by Jim Creybohm
The symptom of 'Error' after starting to move the card is very often due to problems with that finger contact.
To answer your questions :
1) The finger contact is lifted by plastic (nylon?) balls as the card moves through the reader. The ends of the fingers touch contacts on the back of the keyboard PCB.
There are 3 balls and thus 3 contact fingers. One lifts as the card is inserted to turn on the motor. The next lifts when the card is over the read/write head, and starts read/write. The last detects the cut-off corner of the card (it lifts later if the corner is cut) and is used for write protection.
I believe that if there's bad contact on these 'switches' then you get the 'Error'. In other words if one opens too early, or makes and breaks again due to too little contact pressure or dirt, you get thise problem.
2) You could try disconnecting the motor from the card reader PCB (note the polarity!) and run it from a 3V battery or similar. If that will pull the card through, the roller is probably OK.
3) There are ways of detecting wear in a magnetic head (often you
notice the drop in self-inductance of the head winding as the gap
gets worn larger), but I have no idea what the 'right' value for
a 67 head would be, or how far worn it can be before you have problems.
Over-use of the cleaning card will wear the head (to the extent that I never use this card, I take the machine apart and clean the head by hand). I've never found a head too worn to work, though.
I would start by cleaning (propan-2-ol, and if that doesn't work, a careful rub with an ink eraser) the contacts on the keyboard PCB and the ends of the finger contact. If that doesn't help, look at the fixing screws for the finger contact. The 2 at the end are for fixing it and should be tight. The other 3 are adjustments for each
'switch'. Try screwing them in _slightly_.