HP Forum Archive 15

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repairing card reader motor on HP-65? Message #1 Posted by Mark Crispin on 2 Aug 2005, 7:26 p.m. I have an HP-65 whose card reader motor squealed when I first got it (but otherwise worked). As time wore on, the motor got more intermittant in its performance, and now seems to have died. Is the motor repairable? Or can it be readily replaced? If so, how?

Repairing card reader motor on HP-65? (just a possible cause) Message #2 Posted by Vieira, Luiz C. (Brasil) on 2 Aug 2005, 7:29 p.m., in response to message #1 by Mark Crispin Hello, Mark; I'm not aware of how the motor is connected to the main voltage supply in the HP65, I guess it is through a transistor (PWM?). In this case, have you considered the possibility of having a good motor and a bad solid-state switch? I'm sure others will come with more info, so it's worth waiting for other posts. Best regards. Luiz (Brazil) Edited: 2 Aug 2005, 7:30 p.m.

Re: Repairing card reader motor on HP-65? (just a possible cause) Message #3 Posted by marais on 3 Aug 2005, 4:09 a.m., in response to message #2 by Vieira, Luiz C. (Brasil) I recomment to unsolder the motor and drive it directly with a 1.5V power supply. There's a capacitor parallel to the motor, the dot indicates plus. The motor alone should pull about 7-9mA. I would carry out this test before looking any further. Andreas

Re: Repairing card reader motor on HP-65? (just a possible cause) Message #4 Posted by Tony Duell on 3 Aug 2005, 3:46 p.m., in response to message #2 by Vieira, Luiz C. (Brasil) The motor control circuit is built into the sense amplifier chip (Only HP would try and put a low-level read amplifier and a DC motor controller on the same chip, only HP could get it to work :-)). It's possible that it's failed. The sense amplifier chip is the one on the card reader PCB, of course. As others have suggested, disconnect the motor from that PCB (on most 65s the wires are soldered in place) and run it from a 1.5V -- 3V PSU. If it doesn't run, take the motor out (2 tiny screws alongside the worm gear) and try it again. If it runs properly now, look for mechanical problems. If the bare motor doesn't work, try putting 1 drop of watch oil (not WD40!!!) on the bearings. That may get it going again. I have never tried to open up one of these motors, but it might be possible.

Re: Repairing card reader motor on HP-65? (just a possible cause) Message #5 Posted by Mark Crispin on 7 Aug 2005, 1:23 p.m., in response to message #4 by Tony Duell OK, I unsoldered the motor and determined that it does run. I removed the motor, gave it power, and determined that it runs but squeals. I gave it a tiny drop of Break-Free CLP as suggested, and that solved the squealing. I reinstalled the motor, and while still disconnected gave it power. It can pull a card through. I suspect that some lubrication in the card reader's roller would make it run a bit smoother but I decided not to do anything about that, for fear of possibly making it worse. I reconnected the motor. I'm back to where I was before; there is no obvious attempt to pull the card through. I tried measuring voltage across the motor leads and didn't see anything, which would certainly explain why the motor wasn't running. So, what now?

Re: Repairing card reader motor on HP-65? (just a possible cause) Message #6 Posted by Mark Crispin on 7 Aug 2005, 8:06 p.m., in response to message #5 by Mark Crispin Update: Just now, when I poked a card in it, it grabbed the card and then stopped. I tried a couple of additional times, including inserting the card just shy of where it could be grabbed, and I saw the start then stop behavior. I already know the motor turns with externally applied power (see previous messages), and even pulls a card through. So it's not excessive friction So, this suggests that a sensor and/or switch is intermittant. What now?

HP-65 card reader behavior has changed! Message #7 Posted by Mark Crispin on 8 Aug 2005, 1:33 a.m., in response to message #6 by Mark Crispin The behavior has changed yet again. Now, if I insert a card very slowly until it reaches the sensor, it starts running the motor (it didn't do this before) but as I move the card forward it stops. It hasn't reached the roller yet (there's at least another millimeter or two before that) when it stops. This definitely suggests some kind of sensor or switch problem. Any suggestions on how to proceed?

Re: HP-65 card reader behavior has changed! Message #8 Posted by Tony Duell on 8 Aug 2005, 11:02 a.m., in response to message #7 by Mark Crispin If you look at my HP65 notes (in the articles forum on this site), or better still get the HPCC schematics disk, you'll see there are 3 switches in the card reader assembly. Physically there's a leaf contact on the chassis that touches pads on the keyboard PCB when the card lifts it (via little plastic balls). The 3 contacts detect a card has been inserted (and start the motor), detect when the card has got to the head (to start reading/writing), and detect if the corner has been cliped. My next move would be to use an ohmmeter to check these switches (chassis/keyboard screwed into the top case, but the logic board unplugged) as you put a card in by hand. Most likely there's a problem with them. Remove the keyboard assembly and clean the contacts. I normally wipe them with propan-2-ol first, and if that doesn't get them going, I gently clean them with an eraser (!).

it's working again! Message #9 Posted by Mark Crispin on 8 Aug 2005, 7:56 p.m., in response to message #8 by Tony Duell It's changed again. After three weeks of non-functioning, it's working again, pulling the cards through without hesitation or problem. I guess that this means that some debris got into those switches, and it's now cleared. Thank you to everybody. You're a great bunch of people (but you knew that already).

Re: repairing card reader motor on HP-65? Message #10 Posted by David Smith on 3 Aug 2005, 4:15 p.m., in response to message #1 by Mark Crispin Squealing motors can be caused by two things. One is the tip of the worm gear rubbing on a steel ball in the reader housing (not all readers seem to have the steel ball). The other is the motor ball bearings (usually at the motor shaft end). The cure in each case for me has been a drop of Break-Free CLP gun lubricant. I apply it with a small disposable paint brush. It takes about an hour for the lube to work it's magic. Don't over do things. Lube on the motor shaft/work gear friction fit coupling can cause it to lose grip... but this happens to almost all readers over time. Now I always remove the worm gear, clean the shaft with alcohol, and reglue it with a very small amount of IC-2000 Tire Cement (a black rubbery super glue).

Re: repairing card reader motor on HP-65? Message #11 Posted by Mark Crispin on 4 Aug 2005, 2:49 p.m., in response to message #10 by David Smith I don't know if this is relevant or not. As the squealing card reader failed, it increasingly failed to feed the card, including the card being stuck entirely in the calculator. Repeated power cycles were needed to move the card enough that it could be pulled out. Now, the motor makes no obvious attempt to run at all. Being a good gun nut, I have Break-Free CLP on hand. But I'm a bit reluctant to "go in" without explicit instructions on exactly what to do. We can take this to email. I'm mrc at washington.edu. Or, if someone is local to the Seattle area, I'm willing to spring for a few beers in return for helping me get this working again.

Re: repairing card reader motor on HP-65? Message #12 Posted by Bernhard on 5 Aug 2005, 4:02 p.m., in response to message #11 by Mark Crispin Hi Marc, a brief glance over your posts does not tell whether the card drive wheel was properly replaced (or did I miss something ?). If you still have a decomposing "gummy wheel" that wasn't replaced or a wrong replacement (diameter too large, material too stiff) then it is easy to get the symptoms you describe (or even ruin the motor). Did you open the calculator and inspect it (no further disassembly needed). Another tip: never, never use any oil or grease while the motor (or any other component to get lube) is in the calc. After some really big mistakes and lots of trouble I do now only apply oil / grease to HP card mechanisms when the parts are out and far away from the rest and the general idea is to apply it very very sparingly. The card reader ain't no gun, it's more than a wristwatch clockwork, and easily turned into a hopeless case. Before you even try to disassemble the card reader itself, read the card reader repair instructions available on this site. best regards, Bernhard

Re: repairing card reader motor on HP-65? Message #13 Posted by Mark Crispin on 6 Aug 2005, 11:17 p.m., in response to message #12 by Bernhard Yes, the wheel was replaced before I got it.

Re: repairing card reader motor on HP-65? Message #14 Posted by David Smith on 8 Aug 2005, 11:43 a.m., in response to message #13 by Mark Crispin I would suspect that the coupling between the motor shaft and worm gear has either decomposed or come loose. If it is just loose, you can fix it with a drop of glue. I use IC2000 tire cement, a rubberized superglue used to secure RC car tires. If it is completely decomposed, you can replace it with a piece of the spray tube from a can of (egad) WD-40.

Re: repairing card reader motor on HP-65? Message #15 Posted by David Smith on 8 Aug 2005, 11:48 a.m., in response to message #13 by Mark Crispin I forgot to mention that to tell if the shaft coupling is at fault, remove the motor/worm gear (two screws) and give the gear a gentle pull. If it comes off the motor shaft, you have found your problem.

Re: repairing card reader motor on HP-65? Message #16 Posted by Mark Crispin on 8 Aug 2005, 12:07 p.m., in response to message #15 by David Smith That doesn't seem to be the problem; see other messages in the thread. I'll take a look at the switches.

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