67 card reader problem - help!



#11

I buy HP-67/97 calculators on eBay, fix them and sell them under username davehal2001. I have successfully repaired numerous card readers without any serious problems - until now. Mark Hoskins (waterhosko on eBay) recommends I bring this problem here, indicating there is nothing you folks cannot solve.

So here goes:I have a problem with a 67 card reader and I cannot solve this problem myself. This card reader has the gummy wheel repair complete. The clutch works as is, so it has NOT been repaired; the reader pulls the cards through VERY well. The problem is, when I run a card through, I get an error message almost every time, mostly when I try to read cards. About half the time I write cards it works. The other odd thing is it seems the motor "runs on" for a fraction of a second after the card is finished going through. I have checked the finger contacts and they seem to be connecting properly. Any ideas?

Thanks,

Dave


#12

Did you change the capacitors? I solved problems like this by changing the capacitors on the card reader PCB and some on the Logic PCB. I have a low-resolution photo where I have marked the position, polarity and value of the capacitors. I can email it to you.


#13

Klaus,

Thanks! I don't know if my soldering skills are up to it, but please send the photo to dmbowman@mchsi.com. Thanks!

Dave

#14

Dave, I don't have an answer for you. I hope you find one.

The sickening "run on" noise is one I am well familiar with. It is a generic symptom of a failed card reading. In my experience, it accompanies almost all HP67 card reading failures. I don't know what it means for sure. I do know that when it doesn't happen and the card still fails to read, that means usually corrupt card--the card passed normally but the calculator seemed to find no data at all.

I recently received an expertly restored HP67 and I must admit that coping with the sensitivities and idiosyncrasies of the card reader is enough to drive me nuts. I have learned a few things:

1. I try to do card reading and certainly writing with the thing plugged into AC. When the battery begins to flag even slightly, the motor gets sluggish, cards pass too slowly and sometimes get stuck, read failures occur and, most importantly, write failures occur even though the calculator gives no indication that this has happened. Indeed, I have been running my HP67 lately on AC trickle charge most of the time. Yes, scandalous I know!

2. I wash my hands before handling cards. Seriously! I had pizza for dinner one night this week, and evidently my fingers were more oily than I thought, since cards would not feed normally, would get stuck even with a full charge and AC power. Alcohol cleaning of the cards, a thorough handwashing, and a single pass of the evil red card was required to keep the oily residue from propagating further.

3. Inserting the card requires gentleness and good timing. Push it slightly too quickly, it will pass a little too quickly and misread. Hold onto it just a little too long when the motor engages, and that messes things up too. Getting the "touch" has taken me lots of practice.

4. When writing cards of something important I make multiple backups. As I get more comfortable I probably won't be so obsessive about this.

I recently acquired a plasmoid refurbished HP41 card reader and have found it much more forgiving, provided that the calculator is working properly and the batteries are good. Indeed, plasmoid is quite clear that read/write errors should be an uncommon occurence in a working card reader. However, I do know that my errors on the HP67 are getting fewer with experience and practice. I am glad I have the HP41 card reader, though--since it can read and translate HP67 cards, and is more robust in general, if I get repeat errors on a card passing it through the HP41 reader is diagnostically useful since error messages are more specific. For example, CARD ERR almost certainly means bad card, whereas MALFUNCTION or no error at all means the card probably needs good cleaning before the fussier 67 will accept it, or there is something localizable to the HP67 (usually flagging power, or olive oil on the pinch rollers!!!!).

I really hope you solve your problem. A working card reader on these old calcs is a joy, and I really appreciate why our forebears in the 70s were so amazed by the 65 and 67. But a goofy card reader is sort of frustrating and sad, since you just can't tap into the mystery and power of these old machines if you can't save your programs.

Good luck, and keep us posted--

Les


#15

I am not kidding. Back in the days that I was working regularly with TI-59's there were a number of recognized remedies for card reader problems such as running with the charger connected, installing a new battery pack, rounding the corners of the magnetic cards, and cleaning the card with alcohol or distilled water. I was having difficulty reading a card with a known good card reader and didn't have alcohol or distilled water readily available so I put a little spit on a handkerchief and wiped the card. Voila! It read like a charm. After finding that the method worked better than alcohol or water with other problem magnetic cards I told others about it. They were always skeptical, but when they tried it they were often successful.

The spit technique did help with one difficult to read HP-67 card. I don't claim to understand why this works. Perhaps spit is just a superior solvent for oily residue.


#16

Quote:
Perhaps spit is just a superior solvent for oily residue.

I think it may be a matter of displacement, as saliva is mostly water, hydrophilic vs. hydrophobic, that sort of thing.

Saliva contains some lipase, the enzyme that lops the fatty acids off of their glycerol backbone in biological fats and oils, but doesn't kick in until the low pH in the stomach.

But spit is filled with stuff that makes it viscous and sticky--mucopolysaccharides and glycoproteins, for example. A light film of this on the card may be enough to assist the card reader to grab and pull a rogue card rendered slippery by a grease spot.

Seems plausible?

Les

Edited: 24 Mar 2007, 9:10 a.m.

#17

Quote:
I recently acquired a plasmoid refurbished HP41 card reader and have found it much more forgiving, provided that the calculator is working properly and the batteries are good. Indeed, plasmoid is quite clear that read/write errors should be an uncommon occurence in a working card reader.

I second that. I used to own an HP-41C (later replaced by a CX) with card reader. I used the card reader pretty heavily for several years, writing programs that spanned half a dozen cards or more, using data cards etc. -- and in all that card reader usage, I never had a single read or write error.


I would expect a properly restored card reader to be very reliable as well, provided the electronics are OK -- others have mentioned the need for a stable power supply (problems with electrolytic capacitors going bad etc.). If you're not doing so already, you could also try running the calculator off NiMH batteries instead of NiCd.

Good luck!

- Thomas


#18

Quote:
I never had a single read or write error.

I don't have quite so perfect a record, but when I do have misreads on the HP41 there is a good reason--crud on the card, sluggish batteries, inept insertion.
Quote:
If you're not doing so already, you could also try running the calculator off NiMH batteries instead of NiCd.

There has been some talk around here recently about building custom NiMH pacs for the Classics, but the sense I got was that the calculator's charging system couldn't do them justice. So I have a waterhosko NiCad pac, and am getting Randy to build me another one with the high quality cells he uses. The waterhosko pac is better than an older pac I have, and I think Randy's pac are better than waterhosko's (though corresponding more expensive).

But I like to use NiMH when I can. The self-fashioned pacs in my Spice calculators run forever, and the 2650mAh NiMH Duracells in my 82240B printer have been charged fully only once and are still powering the printer with a battery rating of 3 almost three months later.

Les


#19

Of the 41 program and data cards in the Standard Pac and Surveying Pac, I have culled 8 that I know for sure do not work and need to be rerecorded.

As for the remaining 33 (65 sides of programs and data), I am happy to report that after charging the HP67 fully with the waterhosko battery pack I have been able to pass these 65 sides thru the card reader with battery power alone two times around so far without generating a single error.

So there is a learning process here.

Les

#20

Quote:
I recently received an expertly restored HP67 and I must admit that coping with the sensitivities and idiosyncrasies of the card reader is enough to drive me nuts.

I would just like to point out that properly rebuilt HP67/65/97/82104A card readers are all extremely reliable. They should work reliably right up to the point of low battery indication. Read/write errors should be very uncommon. It sounds like your HP67 has some issues which need to be resolved.

That having been said, everything Les says about keeping your cards clean is excellent advice -- even a nearly microscopic bump of "crud" on a card can lift it out of contact with the head and cause a read/write error.


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