HP-65 Card Reader Problem Help

[Phoenix Rob]

Hello all,

I have been a viewing this site for many years but decided to join today! I have an HP-65 that has a card read/write problem. I replaced the gummy wheel and now the cards pass through without problems, but I cannot read or write. Can someone with experience in this area point to what I should check to fix this problem? Also, how critical is the card reader speed?

Thanks!

Rob

[PANAMATIK]

(06-08-2015 10:43 PM)Phoenix Rob Wrote:  Hello all,

I have been a viewing this site for many years but decided to join today! I have an HP-65 that has a card read/write problem. I replaced the gummy wheel and now the cards pass through without problems, but I cannot read or write. Can someone with experience in this area point to what I should check to fix this problem? Also, how critical is the card reader speed?

Thanks!

Rob

I'm not an expert. But as no expert seems to be here, I try to give an answer.

I replaced the gummy wheel too in my HP-67 and HP-97 this week and had the same problems. Reading sometimes works and sometimes not. Some of the standard pac cards are readable, other not and the same cards are sometimes readable and sometimes not. I assume that this unreliability depends on speed. The remaining friction of the gummy wheel material could be responsible for different speeds. But I don't know how sensible the card reader is against too low or too high speeds. Is 5 percent tolerable or not? What is the nominal speed? Does it depend on battery state. I don't know.

Unreliable read can also be caused by other reasons than speed, signal quality for example. Are the cards magnetic recordings still ok?

Next week I will try to do some experiments. I will measure the motor speed and I will drive the motor by an external regulated voltage to find the best motor speed for reading the cards. Then probably I can give more answers.

And I have a question too. Still I don't fully understand the 'clutch' problem. And I don't know if I have this problem in my calculators. If the "clutch" is faulty, does it cause only speed variations, or does it cause stopping the wheel? Any experts there?

Bernhard

[Dave Frederickson]

If we consider that the 65/67/97/41 card readers are similar, then motor speed is rather important. That's why the 41 diag ROM has a specific card reader speed test and the 97 service manual has an extensive section on adjusting the motor speed.

I highly recommend you watch Geoff Quickfall's video from HHC 2014 on card reader repair.



Pay particular attention to the part about the "clutch" which is really a dampening coupler.

Edit: The HP-67/97 uses the card reader for the HP-65 so I think the HP-97 service manual is a good reference. The HP-41 card reader has closed-loop speed control whereas the earlier card reader uses an open-loop design.

Dave

[Geoff Quickfall]

Sorry for tardy reply,

the speed is important and may be varied in the 67 and 97 with a variable resistor. The 65 has a soldered fixed resistor.

The problem is most likely the height of the pinch roller. This can be adjusted to release or apply pressure to the card as it passes over the read head. As the card pressure on the release head increases the current used by the motor increases. In the 97 manual it tells you the optimum current draw for the motor, hence the correct height of the pinch roller.

Without fancy oscilloscopes and etc. one can manage to hit the peak performance of the unit. I have had many card readers either read or write but not both, but with height adjustment of the pinch roller I have had success. The following assumptions are made, and they are not beyond reason:

- The resistor controlling the speed is good.
- all solder joints are good
- the wires to the reader are reinserted correctly
- the caps are good
- the "clutch" which is not a clutch but a vibration damper is good and the pinch roller material substitute is good.

What can go wrong? Well the material used to replace the pinch roller is probably slightly different in its OD. Logically, this is the difference as it is the only thing changed. That is, resistors don't die just because you looked at them. How to adjust the height? The axle with the slot holding the pinch roller in place is actually an eccentric cam. By rotating it through 360' degrees you raise and lower the pinch roller.

It is a matter of finding the sweet spot, either through the current draw method or the trial and effort method.

I repair all that can be physically; the dampening couple and the pinch roller, check all connections and solder joints. Then reassemble but leave the back off. I fashion a tool with a 90' bend in it ( one leg of pair of tweezers ) to access the slot and turn the eccentric cam. Run the card through to write a short program, switch to run and run the card through to read, adjust the cam, repeat, adjust, repeat...

Actually did this to Steves 67 at the 2014 meeting, I had to replace the o-rings someone had used to replace the pinch roller gummy wheel. The o-rings had hardened and were eroding on the surface causing his machine to read but not write, that is the pinch roller height due to erosion of the surface had reduced. I replaced this with the silicon tubing fix, adjusted the height and voila, done.

Geoff

Quick edit, Dave is correct, the speed is very important, my point is to attempt to adjust the pinch roller first before any components a swapped. Anecdotally I have varied the speed rather dramatically and still had successful read and writes. But there is a design sweet spot for the speed, and of course any card written must be readable by another machine, so a standardized speed is required.

[Massimo Gnerucci]

(06-13-2015 12:44 PM)Geoff Quickfall Wrote:  Sorry for tardy reply,
(...)
Geoff

Thanks Geoff, that's exactly what I can read in your book!

;)

[Phoenix Rob]

Thanks for all the replies (especially Geoff). I will try the suggestions. I do have a few questions.

1. Geoff - Where can I buy the Mil Spec tubing? Do you have a P/N?

2. Can someone verify the correct wiring of the read/write head, motor and power? I may have swapped a couple of wires - I have connected the wires reading left to right as follows:

Red (pwr), Black (pwr), Black (motor), Red (motor), Dark Brown (head), Black (head), Light Brown (head), Red (head), Blue (head).

Rob

[Geoff Quickfall]

Standby, on a flight to Australia, will post correct order for wiring.

Geoff

[PANAMATIK]

(06-14-2015 04:09 AM)Geoff Quickfall Wrote:  Standby, on a flight to Australia, will post correct order for wiring.

Geoff

I'm standby at home and I might provide you faster than Geoff with some information. My HP-67 has different wire colors than yours, but you can see the correct order from the image below.

   

I hope you will have a working card reader soon!

Bernhard

[Phoenix Rob]

Bernhard,

I have an HP-67 and the head wiring colors are different than the HP-65. Due to the color differences I don't see how I can use an HP-67 to verify the HP-65 head wiring.

Regards,

Rob

[PANAMATIK]

(06-14-2015 11:31 PM)Phoenix Rob Wrote:  Bernhard,

I have an HP-67 and the head wiring colors are different than the HP-65. Due to the color differences I don't see how I can use an HP-67 to verify the HP-65 head wiring.

Regards,

Rob

Sorry I don't have an HP-65. I thought, that the arrangement of the wires could be some help, if they are similar in the HP-65, independently of the colors.

Anyway you will get Geoff's description soon.

Bernhard

[TonyTr]

Hope those below pictures could help in anyway.

https://dl.dropboxusercontent.com/u/2450...C_6774.jpg

https://dl.dropboxusercontent.com/u/2450...C_6775.jpg

https://dl.dropboxusercontent.com/u/2450...C_6776.jpg

https://dl.dropboxusercontent.com/u/2450...C_6777.jpg

https://dl.dropboxusercontent.com/u/2450...C_6778.jpg

[Phoenix Rob]

Tony,

Thanks for the pictures. My HP-65 colors do not match the pictures for some reason. I have a brown wire and the pictures don't. Maybe the colors have faded over time.

Regards,

Rob

[Phoenix Rob]

Geoff,

When you have time, can you answer my 14 June post questions?

Best Regards,

Rob

[Geoff Quickfall]

Monday!

[Etienne Victoria]

Hi,

On my Superstar Card Reader repair sequence : Here

Picture 24 gives the wiring.



and the diodes :



Etienne

[Etienne Victoria]

And on this very Museum, Matt Riehl gave the wiring scheme : Here in 2000



Credits : Matt Riehl & Hpmuseum.

E.

[Phoenix Rob]

Etienne,

Thanks for the detailed wiring info. Using your input I was able to verify that my calculator wiring is correct. My calculator still has read/write problems. Does anyone have any suggestions on what to check next?

Regards,

Rob

[Geoff Quickfall]

Try adjusting the height of the pinch roller by rotating it through 180 degrees using the slot in the pinch roller axle.

I fastened a 'screw driver' for the slot by bending a stiff metal arm from a pair of tweezers. This so the adjustment can be made while the pinch roller is in situ. Adjust the axle by a few degrees, then test a write then read. Adjust again and test, again and test. Once through 180 degrees you are repeating the height cycle. I test through the next 180 degrees just in case I missed the sweet spot.

I did not post the wiring pics as Etienne beat me to it. Comment somme vous Etienne?

Geoff

[Phoenix Rob]

Geoff,

I measured the pinch roller pin and it is perfectly symmetric. I don't see how rotating the pin will affect the head height. Also, do you have a P/N for the pinch roller surgical tubing?

Regards,

Rob

[Geoff Quickfall]

Actually it is an eccentric cam, albeit very slight and it does adjust the height of the pinch roller. This does affect the read and write ability. I have adjusted units that write only and turned them into read only. Then adjusted back to the units sweet spot to have read/write working.

I will dig up the manufacturer of the tubing I use and post it.

geoff