HP-67 Card reader repair



#2

I have an HP-67 calculator that has been working great for years. I bought it on ebay from Mike Davis back in 2002 and up until just recently, it has seen little use. I decided this year to sell it. I felt it wasn't getting the proper respect it deserved since I aquired an HP-41, and it would be better off in the hands of another collector. When I got it out, I was dissapointed to find the card reader didn't function.

I'm going to summerize a long story: The calculator would pull cards through ok, but would emit a slight screech at the end of the read (like it was still trying to pull a card through when there was none left) and would display "error." First I suspected it was the "gummy wheel" problem, but I found the wheel wasn't gummy in the least. Then I looked into some guides online, and decided that the clutch must be going out. I used Mark Hoskins guide to repair the clutch via the less than ideal (but only method I could manage) super-glue method. The motor now feels and sounds (is more noise good?) like it has signifigantly more power, but still fails to read and write. I'm pretty novice at these repairs, and don't have a clue what to do beyond this point.

It seems to pull cards through fine, but entirely fails to read/write data to/from the card. I'm at my wits end. Any idea what could be the problem, or where I should even start to look?

Your help appreciated,

-Erin


#3

I would suspect one or more of the reader leaf switches is misadjusted. Since the motor seems to be starting properly the MOTOR switch is OK. I would first check the HEAD switch.

When you insert a card you should see the MOTOR switch close first, the the HEAD switch, then the WRITE PROTECT switch. If you don't have Tony Duell's excellent HP classic notes, you can trace the contacts on the back of the keyboard to the pins going to the CPU card.


#4

Quote:
I would suspect one or more of the reader leaf switches is misadjusted. Since the motor seems to be starting properly the MOTOR switch is OK. I would first check the HEAD switch.

When you insert a card you should see the MOTOR switch close first, the the HEAD switch, then the WRITE PROTECT switch. If you don't have Tony Duell's excellent HP classic notes, you can trace the contacts on the back of the keyboard to the pins going to the CPU card.


Sounds logical. I assume you are talking about those gold plated contacts inside the calculator. Is the a diagram somewhere of which contanct is which? (motor/Write Protect/head)

Thanks for the quick reply.


#5

While there is no service manual for the HP-67 (to the best of my knowledge), the MoHPC CDROM collection includes the service manual for the HP-97. Given identical architectures and the numerous similarities in the hardware of the two machines, I'd encourage anybody how wants to repair an HP-67 to check out this manual.

There is also of course the circuit diagrams made by Tony Duell. The CDROM with these is available from the UK user's group (http://www.hpcc.org/cdroms).

**vp


Edited: 23 Jan 2006, 11:24 a.m.

#6

You can figure out what switch is what by the position of the nylon balls that press the gold leaves, but you really dont need to. Just make sure that each switch opens and closes cleanly as a card is inserted and removed. The switches are adjusted by turning the little screw at the base of each leaf. Generally you can crank down the screw until the switch is closed without a card in and then back it off a eigth to a quarter turn or so until the switch opens up. Then check with a card.


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