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HP-41 Card Reader NOT gummy wheel problem
Message #1 Posted by Rich Forest on 3 Jan 2009, 11:45 p.m.

I have a card reader that feeds cards OK, writes OK, but cannot read cards. My HP displays "CARD ERR" each time I feed a card through. I cleaned the contacts on the interface side, reseated the vertical PCB inside the reader, and soldered the head wires directly to the PCB (to discard bad connections), and still no luck. The head works, because I swapped it from a spare card reader. Has anyone experienced a similar problem? What else can I check?

      
The pinch roller axle is assymetric;..........
Message #2 Posted by Geoff Quickfall on 3 Jan 2009, 11:57 p.m.,
in response to message #1 by Rich Forest

Has the white plastic spindle (axle) that the pinch roller sits on been turned? It must have as the gummy wheel has been replaced.

Try rotating the axle which is assymetric. By rotating the axle you raise or lower the spindle and therefore the card; which in turn can affect the distance the card is from the card reader head. You can do this using the slot built into the axle. I fashioned a tool with a tiny 90 degree bend at the end which I can then maneouver into the slot.

I have repaired about 20 card readers from the 65 to the 41 and have had the same problem on occasion. Rotating the axle to correct the card to card reader interface has fixed this on the few instances that it occurred.

Cheers, Geoff

Edited: 3 Jan 2009, 11:57 p.m.

            
Re: The pinch roller axle is assymetric;..........
Message #3 Posted by Karl-Ludwig Butte on 4 Jan 2009, 12:06 p.m.,
in response to message #2 by Geoff Quickfall

Hello all in this thread. Because my unit has a similar problem I tried Geoff's suggestion of turning the axle 180 degree around. Alas, I got the same error as before. As Rich, I'm getting no error message while writing a card. Reading the card produces either "Card Err" or "Malfunction". Sometimes reading a card leaves a "LBL 67 Stop END" program sequence in memory. Is there no check for writing cards ? Alas, I can't try out cards written by the defective unit 'cause I don't have another working one.

Any additional suggestions for trouble shooting will be very much appreciated.

Thanks to you all

Regards

Karl

                  
Re: The pinch roller axle is assymetric;..........
Message #4 Posted by Geoff Quickfall on 4 Jan 2009, 12:45 p.m.,
in response to message #3 by Karl-Ludwig Butte

Hello all,

I always try to eliminate the mechanical problem first.

Karl, 180 degrees is not always going to fix the problem. Since the axle is assymetric and may not be at it's maximum low or high position then try turning the axle 20 degrees at a time. Your 180 degree turn may just have returned the pinch roller to the exact same height you started out with.

It sounds tedious but it is definitely simpler then swapping out components. I am saying that one turn on the axle is not going to necessarily fix the problem. It may take a few attempts. Thats why the slot was put in the axle.

Once th

                        
Re: The pinch roller axle is assymetric;..........
Message #5 Posted by Karl-Ludwig Butte on 5 Jan 2009, 8:14 a.m.,
in response to message #4 by Geoff Quickfall

Hello Geoff,

thanks for the additional explanations - I'll try it out.

Kind regards

Karl

                        
Re: The pinch roller axle is assymetric;..........
Message #6 Posted by Karl-Ludwig Butte on 6 Jan 2009, 3:50 a.m.,
in response to message #4 by Geoff Quickfall

Hello Geoff,

I'd like to thank you very, very much. Your hint worked pretty well. My card reader works now as smooth like new.

Kind regards

Karl

                              
Excellent, yes the assymetric pinch roller axle..
Message #7 Posted by Geoff Quickfall on 6 Jan 2009, 4:46 p.m.,
in response to message #6 by Karl-Ludwig Butte

is not something everyone checks.

My HP 65 that I restored kept reading but not writing. After manipulating the axle I now have 100% read and write.

Glad it worked,

Cheers, Geoff

                        
Re: The pinch roller axle is assymetric;..........
Message #8 Posted by william tomaselli (Turin-Italy) on 12 Jan 2009, 5:49 a.m.,
in response to message #4 by Geoff Quickfall

Sorry Geoff, the axle you are talking about is the very little white and vertical plastic axle around which the white roller turns? If yes, how can I turn it of 20 degrees? Thank you by william

Quote:
Hello all,

I always try to eliminate the mechanical problem first.

Karl, 180 degrees is not always going to fix the problem. Since the axle is assymetric and may not be at it's maximum low or high position then try turning the axle 20 degrees at a time. Your 180 degree turn may just have returned the pinch roller to the exact same height you started out with.

It sounds tedious but it is definitely simpler then swapping out components. I am saying that one turn on the axle is not going to necessarily fix the problem. It may take a few attempts. Thats why the slot was put in the axle.

Once th


      
Re: HP-41 Card Reader NOT gummy wheel problem
Message #9 Posted by Ignazio Cara (Italy) on 4 Jan 2009, 4:55 a.m.,
in response to message #1 by Rich Forest

How many tanthalum condenser there are on the auxiliary PCB (vertical PCB)? Perhaps two or three: if you can see the writted value on each, you must replace the 6,8 uF unit with a good spare. Let me know.

Ignazio

      
Re: HP-41 Card Reader NOT gummy wheel problem
Message #10 Posted by Randy on 4 Jan 2009, 8:17 a.m.,
in response to message #1 by Rich Forest

Quote:
Feeds OK, writes OK, but cannot read cards

Assuming you can read the card written by the bad unit in another good unit:

Replace the 6.8uf tantalum capacitor that is soldered across the two motor terminals.

Edited: 4 Jan 2009, 8:25 a.m.

            
Re: HP-41 Card Reader NOT gummy wheel problem
Message #11 Posted by Rich Forest on 4 Jan 2009, 9:34 a.m.,
in response to message #10 by Randy

I used the complete motor and card reader head assembly from a working unit and I get the same error message. This assembly (motor, head, switches, wheel, etc.) works OK in the other unit. I did not swap the vertical card since I had already soldered the color wires to it to discard bad connection problems. Neither the motor cap nor a bad head seem to be the issue. The card written CAN be read in another reader. So can this problem be related to a bad cap in the vertical PCB? Is there a way to measure voltages to check for bad caps here? How does the reader chip work? Thanks for all of the suggestions.

                  
Re: HP-41 Card Reader NOT gummy wheel problem
Message #12 Posted by Randy on 4 Jan 2009, 10:59 a.m.,
in response to message #11 by Rich Forest

Quote:
I used the complete motor and card reader head assembly from a working unit

So you have eliminated/swapped out all parts except the bottom pc board, the one with the three IC's on it, correct? I'm assuming thats what you mean since the vertical board is soldered to the head wires...

If that's the case, it might be a bad CRC IC (1LA2-0001). Cannot think of anything else that would cause the problem.

                        
Re: HP-41 Card Reader NOT gummy wheel problem
Message #13 Posted by Rich Forest on 4 Jan 2009, 6:46 p.m.,
in response to message #12 by Randy

Pretty much the vertical and bottom PCBs are the components that did not get swapped. I'm still curious about this "bad capacitor" problem which is also mentioned in much earlier posts (a few years ago). I kind of found conflicting information related to that. I'm about to try that, but I can't figure out what values they are. They are painted, and I assume the polarity (+) is marked by the bead on the lead? Also does anyone happen to know/understand how all this circuitry works? I'd appreciate it if you could point me to the right place to read on this. Thank you very much to everyone who has tried to help.

                              
Re: HP-41 Card Reader NOT gummy wheel problem
Message #14 Posted by Karl-Ludwig Butte on 5 Jan 2009, 8:12 a.m.,
in response to message #13 by Rich Forest

Hello Rich,

I found the Service Manual for the Card Reader on that other site. It's very informative on one hand but at the same moment a bit disappointing on the other hand 'cause HP-technicians had a special version of the 41C and a special purpose ROM-module for troubleshooting and calibrating the card reader. Anyway, you may have a look yourself.

Kind regards

Karl

                  
Re: HP-41 Card Reader NOT gummy wheel problem
Message #15 Posted by Geoff Quickfall on 4 Jan 2009, 12:47 p.m.,
in response to message #11 by Rich Forest

That swap out has ruled out my axle fix. It now sounds like something in the main cp board and not the card reader board.

I will leave the electronics testing to others!

Cheers, Geoff

                  
Re: HP-41 Card Reader NOT gummy wheel problem
Message #16 Posted by Ignazio Cara (Italy) on 5 Jan 2009, 2:43 p.m.,
in response to message #11 by Rich Forest

Another help, if you want try again. If your vertical PCB is a 82104-60025 ASSY, the 6,8 uF cap is above the central diode (blue-gray-green from top to bottom). Warning to the polarity ;) Good luck.

Ignazio

                        
Re: HP-41 Card Reader NOT gummy wheel problem
Message #17 Posted by rich forest on 11 Jan 2009, 12:18 a.m.,
in response to message #16 by Ignazio Cara (Italy)

I ran out of time last weekend to finish debugging this issue. But I got back to it today, and I'd like to thank everyone for trying to help. It was the CAPACITOR between pins 17 and 18 of the sense amplifier chip! After much testing various parts, trying to rule out mechanical issues, I found that the problem was related to the sense amplifier board (vertical PCB). So I followed the advice of changing the 6.8uF cap and success! The card reader works fine now!

                              
Re: HP-41 Card Reader NOT gummy wheel problem
Message #18 Posted by Ignazio Cara (Italy) on 12 Jan 2009, 2:54 a.m.,
in response to message #17 by rich forest

Well done! I'm so happy to have helped. Regards from Italy

Ignazio

                                    
Re: HP-41 Card Reader NOT gummy wheel problem
Message #19 Posted by william tomaselli (Turin-Italy) on 12 Jan 2009, 6:23 a.m.,
in response to message #18 by Ignazio Cara (Italy)

Dear Ignazio, I'm not sure of having understood the detailed explanation given by you on the HP Forum. Considering that I'm experiencing the same technical problem with my HP41 Card Reader explained by the other HP members, do you mind my request of contacting you directly by email? Thank you very much William Tomaselli

Quote:
Well done! I'm so happy to have helped. Regards from Italy

Ignazio


Quote:
REPLACE THIS TEXT WITH THE QUOTE
                                          
Re: HP-41 Card Reader NOT gummy wheel problem
Message #20 Posted by Ignazio Cara (Italy) on 12 Jan 2009, 10:59 a.m.,
in response to message #19 by william tomaselli (Turin-Italy)

Sure! You are welcome. Regards.

Ignazio


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