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HP97 questions
02-04-2015, 07:17 PM
Post: #1
HP97 questions
I rescued an HP 97 from my parents' house a year ago. I’m getting ready to sell it, since I don’t have any need for it.

It seems to be in pretty good shape, but I have a couple of questions, which I hope the collected MoHPC wisdom can help me with.

I’m sure the card reader wheels have turned gummy. In fact, I bought an O-ring repair kit on Ebay many years ago so my Dad could fix that. However, he never got around to it. The O-rings are still there, along with instructions on using them to fix an HP67 (with no mention that I see about the '97).

So, first questions) Is this the right kit? Do both calcs have the same card reader internals? Are the repair instructions basically the same? Should I try to fix it? I’m fairly handy - but does that markedly improve the value of the calc?

If I try to use the printer, it seems to be trying to print but the paper does not advance. If I pull the paper out by hand, the printout looks fine.

Second questions) is this another "gummy wheel" problem? Is it easy to fix?

Question 3) is there any self-test for this calculator? I couldn’t find anything on the Museum pages. I’m guessing this is a feature of later generation calculators.

Thanks for your help.
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02-04-2015, 07:38 PM
Post: #2
RE: HP97 questions
(02-04-2015 07:17 PM)Dave Shaffer Wrote:  I rescued an HP 97 from my parents' house a year ago. I’m getting ready to sell it, since I don’t have any need for it.

It seems to be in pretty good shape, but I have a couple of questions, which I hope the collected MoHPC wisdom can help me with.

I’m sure the card reader wheels have turned gummy. In fact, I bought an O-ring repair kit on Ebay many years ago so my Dad could fix that. However, he never got around to it. The O-rings are still there, along with instructions on using them to fix an HP67 (with no mention that I see about the '97).

So, first questions) Is this the right kit? Do both calcs have the same card reader internals? Are the repair instructions basically the same? Should I try to fix it? I’m fairly handy - but does that markedly improve the value of the calc?

If I try to use the printer, it seems to be trying to print but the paper does not advance. If I pull the paper out by hand, the printout looks fine.

Second questions) is this another "gummy wheel" problem? Is it easy to fix?

Question 3) is there any self-test for this calculator? I couldn’t find anything on the Museum pages. I’m guessing this is a feature of later generation calculators.

Thanks for your help.

The O-Rings are the same for the -67 and -97, but the procedure is understandably much different due to the totally different case/housing designs. Once totally disassembled, the core parts are quite similar, but getting it apart is more than half the battle.

Non-advancing paper can have multiple causes, from worn tires to damaged gears, so hard to answer about repair difficulty.

There are detailed articles on both repair procedures in past forum entries, suggest a search (both old and new forums, but mostly old) and of course, Google is your friend.

Both defects can detract significantly from the sale price; since only collectors typically buy them, most want these items working. Each repair costs about $70-$80 if done outside, and probably adds about that much to it's worth, maybe more if cosmetics, color-fade, etc. are all VG+.

Another strategy is to post it AS-IS, and although you will surely get less, it may get snapped up by one of the guys that does these repairs.

Also, manuals, cases, etc. add a lot to price.

There is a diagnostic available on a mag-card, but I guess it won't help much until eader is fixed.

Other true experts will likely add more info if you wait a few days.

--Bob Prosperi
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02-04-2015, 11:27 PM (This post was last modified: 02-04-2015 11:29 PM by Paul Berger (Canada).)
Post: #3
RE: HP97 questions
Further to what Bob said, mechanically the card reader mechanism in the 97 is identical to the 67 except it is mounted differently, it is much easier to get at in the 97. To get to the reader you take out the 6 screws in the bottom cover, then there are another 6 screw holding in a black plastic sub frame and the reader is fastened down to the top of this subframe with three screws.

The cable going to the reader can be a problem, to get it out of the connector I use a piece of thin stiff plastic cut from a plastic bubble pack and insert in between the cable and the contacts on the connector, if you don't use something like this the connector contacts dig into the cable and you will very likely damage it. The other problem with this cable is with its construction. The cable is made up of copper strips laminated between two layer of plastic and they are getting old and may partially delaminate while you are handling it, I have been successful gluing them back together with cyanoacrylate glue, be careful to not get glue on the contact area.

Inside the reader there are 4 white balls and a small white roller, if the feed roll on the reader has degraded to a gooey mess you will likely need to take the top off the reader to clean it be very careful not to loose these parts, but i am sure the instruction you have will mention that.

Depending on your level of mechanical skill replacing the feed roll with O-rings is pretty straight forward, the first one I did worked first try.

For the printer my observation has been the two main causes of erratic paper feeding are 1) the rollers get hard and smooth and 2) if the calculator sits for a long time unused it develops a flat spot where the friction roll contacts the pinch roll. The only solution is to replace the "tires" on the feed roll, I have had good luck replacing them with slices of silicon model airplane fuel line. The bad news is you need to partially disassemble the printer to do this, and again depending on your mechanical skill, this may or may not be a big job.

Edit: Almost forgot there is a service guide on the Museum's documentation memory stick.

Paul.
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02-05-2015, 02:37 AM
Post: #4
RE: HP97 questions
A square o-ring from the http://www.theoringstore.com/ works great for the printer repair.
008 Buna-N Square O-rings - Tetraseals
O-ring Size: 3/16"ID X 5/16"OD X 1/16"CS
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02-05-2015, 03:01 AM
Post: #5
RE: HP97 questions
A word of warning... sometime replacing the reader feed roller is not enough to get the reader to work adequately

I repaired my HP-67 card reader last weekend and replacing the gummy roller was easy and straightforward. But even with the new O-Rings, the card was pulled 2 to 3 times more slowly than usual. The "clutch" was the problem and I had to "fix" it with glue. Even after that the card was pulled at a speed that was still a bit too slow. I got Error 19 times out of 20. So I replaced the resistor with a trimer going from 4.4k to around 8k. Now everything works perfectly!

There are other potential problems that you may be faced with: bad capacitor, and badly adjusted nylon ball switches to name a few, but in my case I did not need to solve those issues.

Obviously as I never did this before I had to do a lot of ready of old MoHPC posts and a lot of experimentation. It took the whole weekend, but it was worth it. :-) Even my wife was impressed with a calculator that can read magnetic cards!!

François
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02-07-2015, 09:13 PM
Post: #6
RE: HP97 questions
In preparation for the repair of a 97 card reader, I've watched Geoff Quickfall's HHC2014 video and read all the recent posts regarding card reader repair and I have a few questions.
  1. Can someone provide a source for the mil-grade silicone tubing? Can anyone comment on this tubing from eBay?
  2. Can someone provide the insulation diameters needed to repair the dampening coupler?
TIA
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02-07-2015, 10:47 PM
Post: #7
RE: HP97 questions
Email sent Dave.
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