HP-65 Card Reader Problem Help

[Dave Frederickson]

According to the Nov '76 HP Journal, the HP-97 uses the same card reader as the 65, so it seems like HP-97 service manual would be a good reference. The 97 service manual describes a procedure for adjusting the eccentric cam while measuring the motor current, but I was unsuccessful trying this. The manual also specifies the use of Magnasee to check the recorded track length when adjusting the motor speed, which I haven't used since the 70's, but this magnetic developer should work.

Dave

[Phoenix Rob]

Dave,

I have a copy of the manual. The manual has a procedure to measure the motor current when a card is inserted just far enough to start the motor (but not letting the card to pass). The manual has a spec of 180 mA, but I measure 80 mA with all positions of the eccentric cam.

Best regards,

Rob

[Dave Frederickson]

(06-25-2015 11:20 PM)Phoenix Rob Wrote:  I have a copy of the manual. The manual has a procedure to measure the motor current when a card is inserted just far enough to start the motor (but not letting the card to pass). The manual has a spec of 180 mA, but I measure 80 mA with all positions of the eccentric cam.

I couldn't get this to work, either, but I think I understand what's going on. By holding onto the card and not letting it pass, this is making the motor work harder, causing an increase in current. Adjusting the eccentric cam varies the pressure on the card, varying the work the motor does, and causing a change in current. If the current doesn't change then it sounds like adjusting the cam is not having an effect on the friction between the card and the roller on the motor shaft.

At this point I'd try Geoff's technique. Just be sure to use a pre-recorded card for the test READs and a blank card for the WRITE's. The magnetic developer should also give a good indication when the proper speed is found. If your card reader uses fixed value resistors to adjust speed, consider replacing the resistor with a 10K trimpot.

As a last resort there are folks on the forum and eBay who'll repair the card reader for around $80.

Dave

[Geoff Quickfall]

Two things:

- it could be that your pinch roller material OD is to small and does not contact the card pressing it against the read head. Therefore the current draw is always the same and low.

- some cards written by other machines may not be readable. They should be but as repairs occur readability varies. So, write a test program, write it to a card then try reading the card. Of course if writing is a problem then use a prerecorded card. Once you get it reading then write it to a blank and try again.

As noted, the correct way is to run the motor under stress and measure the current by adjusting the eccentric cam. The same affect can be done by adjusting the eccentric cam, the. Testing, then adjusting and etc.

Geoff

[Phoenix Rob]

Goeff,

No hurry, but if you can find the time I would like this question answered:

Where can I buy the pinch roller Mil Spec tubing? Do you have a P/N?

I suspect my read/write problems may be due to incorrect diameter of my pinch roller.

Best Regards,

Rob

[Etienne Victoria]

Hi Rob,

I don't know if you'll find Geoff's mil-spec tubing.

Alternatively, I can provide some aquarium spec tubing with which I have restored various 4x, 6x & 97s card readers.

Let me know.

Best

Etienne

[ignazio]

Hi,
Have you tried to measure the resistance of the two coil of the magnetic head?

[Phoenix Rob]

Ignazio,

No I haven't done that yet. Thanks for the tip. I will measure the resistance and report the results back.

Best Regards,

Rob

[e_joubert]

Hello all,
I had the same problem with my HP65. Nothing was present at the output (to the head) of the 1826-0158 when I tried to record a card (measured with an oscilloscope). So I changed this 1826-0158 for a 1826-0322 I took out of a HP82104 (HP-41 card reader) and ... it works fine. One must keep in mind that this 1826-0158 is directly connected to the battery. Woodstock syndrom?
Best regards,
Eric