▼
Posts: 521
Threads: 72
Joined: Jul 2007
Going over some of the 9x series desktop calculators in my collection, I've come up with a couple of questions. First, the easy one:
I fired up my HP-91 for the first time in a few years. Many of the keys are VERY bouncy-- that is, if I press "5", it will enter from two to four "5"s in the display. If I press "X", the result is almost always zero since it registers multiple times.
Some of the keys seem to get better if I press them repeatedly. But I've never seen this problem on a 9x keyboard before. I assume the problem is bouncing key contacts...any ideas? Is it fixable?
The second is harder. I've successfully repaired several card readers and am familiar with the mechanism. It's a simple recipe: disassemble the reader, remove the drive wheel, scrape the gunk off, make sure there's no gunk elsewhere in the mechanism, put on a couple of rubber O-rings from a bag I bought on eBay some years back, and it just works.
But this 97 card reader is giving me fits. Everything seems to work, but the card will not pull through. I can see the drive wheel spinning, but the O ring is stationary, the shaft of the wheel spinning beneath it. OK, I've never needed to do this before, but I applied a touch of glue to the shaft and reinstalled the rings. After a few hours they seem firmly affixed.
But the card still doesn't go through. The motor loads down and eventually the glue broke and the shaft spun under the rings again.
If I remove the motor I can feed the card manually and the wheel turns. However, turning the wheel by hand will not move the card through.
I've had the reader apart all weekend and can't figure out why the drag on the card is so high. Any suggestions for this one?
▼
Posts: 4,027
Threads: 172
Joined: Aug 2005
Hi, David;
a few days ago, Katie Wasserman called our attention to one fact I was aware about and forgot because I never needed to use it. Maybe this is not a solution for your particualr case, but why not to give it a try?
If you take a look at the gear where you built the O-rings, you'll see its axe has an extension with a slot. If you use a small screw driver, you can (gently) turn the axe and, as it is asymmetrical, you'll adjust pressure over the O-rings. If it is not correctly settled, cards will not be pulled.
Just look through the mechanism and you'll see if the o-rings are touching the small "free-wheel" over them or not.
Best regards and success.
Luiz C. Vieira - Brazil
Edited: 1 June 2003, 9:45 p.m.
▼
Posts: 521
Threads: 72
Joined: Jul 2007
I never knew that axle did that! I assume the o-rings should just barely be touching the free wheel?
▼
Posts: 909
Threads: 40
Joined: Jan 1970
Are you sure the free-wheel (the little white roller) is free to turn and not glued in place by old goo? The eccentric shaft on the rubber roller didn't make that much difference on my 97 - I couldn't turn it and cause the motor to essentially stall like you are describing - but I used the silicone rubber tubing and not the O-rings. One thing I've wondered about using O-rings - any O-rings that I've seen have had mold flash sticking out from the outer perimeter. Does that rub off right away when you use them in the card reader?
Posts: 4,027
Threads: 172
Joined: Aug 2005
Hi, David;
and yes: if the O-rings are touching the free whell, than the card itself will do the rest, because of its own thickness. As you mentioned you have already used these O-rings, I thought about the possibility of having different external diam. in some of them, but it seems not.
If you read Ellis post, you'll see another and very important issue there. I used a very, very small amount of silicon glue before "pushing" the O-rings in their assembly shaft. This way, they will not slick off. Anyway, using fuell tubbing seems to be a better choice but I believe tube must be precisely and linearly pushed into the shaft so there will be no irregularities. I have a working card repaired with O-rings and they are not glued, neither they slick (so far). I used silicon glue in another one and, as long as I know, it's still working fine.
Hope this helps, and thanks, Ellis!
Luiz C. Vieira - Brazil
Edited: 2 June 2003, 7:00 a.m.
▼
Posts: 521
Threads: 72
Joined: Jul 2007
The card is feeding now, but at an uneven pace-- you can see the card slow, apparently when it hits the second set of ball switches just after it engages the read/write head. This always produces an ERROR on the display.
The edge of these o-rings is very smooth and I think I'll look for some fual tubing today. I have had these O-rings for several years; perhaps the rubber is hardening and becoming less "sticky".
I need to resolve this soon-- these self-tapping screwings into plastic posts things weren't meant to be taken apart as many times as I've been doing it!
▼
Posts: 909
Threads: 40
Joined: Jan 1970
Those screws in plastic work fine over and over if you take two precautions: always drop the screw into the existing thread by turning counter-clockwise at first until you feel it drop in, and never over-torque (that's the hard one for me to remember).
▼
Posts: 441
Threads: 24
Joined: Apr 2008
Ellis,
Just remember what they say in Detroit:
"Fully driven and seated and not stripped".
Posts: 1,788
Threads: 36
Joined: Aug 2007
I have found most people use size 006 O-rings. These ARE too big (and too hard). The proper size is 005 (15/64 OD). Also the two O-rings tend to slip apart and rub on the sides of the reader well. Fuel line is a MUCH better solution.
Also the shaft coupling between the worm gear and motor shaft sounds like it is loose or broken. I use a rubberized super glue called IC2000 tire cement available at many hobby shops. I dip a 1N4148 diode lead in the stuff and put a drop in the worm gear hole. Too much and you cannot push the motor shaft on all the way. Keep it out of the motor bearings.
▼
Posts: 521
Threads: 72
Joined: Jul 2007
I did use some adhesive to reconnect the worm gear to the motor shaft-- it had spun off. That part seems fine.
I found some tubing I think will work and installed it on the drive wheel.
Unfortunately the end of the ribbon cable that plugs into the card reader module has delaminated to the point where it can no longer be inserted-- the metal connectors are separate from their backing, and the backing's disintegrated enough so that several of the metal connectors no longer have any support.
I see three options:
1. Solder it together. Ick.
2. Find a suitable replacement cable. Unlikely.
3. Use a fairly stiff adhesive film to "relaminate" the end of the cable.
Anyone with any experience here?
▼
Posts: 234
Threads: 33
Joined: Jan 1970
David,
Ribbon cable should be removed with aid from a tool. HP 97 service manual describes a connector tool. I remember that someone mentioned using a brazilian pay phone card (Luiz - was that you ?).
I saw a catalog with samples of ribbon cables for replacement - mostly for microwave oven and other appliances. I was amazed at the quantity - more than 30 types, starting at 5 wires, up to 40 (I guess), with many lengths available. Maybe one would fit the 97. I have a 97, but it is working perfectly, so if you can describe the cable - #of wires, length, width - I can check the store next time (saturday probably).
Also, if I were in your situation, I would consider repairing the cable with adhesive foil. Chomerics and 3M manufature foil (EMI shielding purposes) - useful for 41 battery contacts.
I guess you are having a good time working on the 97 - I had a great time with mine.
Best regards and good luck.
Renato
▼
Posts: 521
Threads: 72
Joined: Jul 2007
I don't think removing the cable hurt anything-- it just pops right out. It's re-inserting it that wears it.
I've taken a photo of the cable with a tape measure against it, but although I know posting photos is possible here I can't seem to figure out how to do it...
Posts: 909
Threads: 40
Joined: Jan 1970
Renato,
See if they have a cable with 13 conductors, 0.1" between conductors, at least 2.75 inches long - with both stripped areas on the same side of the cable.
▼
Posts: 234
Threads: 33
Joined: Jan 1970
Not this saturday, as I expected, but maybe next.
Renato
Posts: 909
Threads: 40
Joined: Jan 1970
Here's an idea I had a while back. I haven't actually done this to my 97 but I intend to next time I have to open it up. (Skip the first part about Molex connectors, the screw machine contact IC sockets are the better idea):
http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/archv012.cgi?read=33029
If you are familiar with this kind of high-quality IC socket you will know what I mean. They come with different diameter pins (that go into the PCB hole) but the 0.020" diameter size pins fit perfectly in the sockets. Make sure you mate gold with gold or tin with tin - never gold with tin.
▼
Posts: 521
Threads: 72
Joined: Jul 2007
Hmmmm...replacing the cable connectors shouldn't be too hard. I've replaced groups of LEDs in the displays of some of the classic calcs before. Looks like single layer circuit boards...I'll look into that this weekend....hope I can find a usable socket!
Posts: 1,788
Threads: 36
Joined: Aug 2007
HP recommends that use use the tool for both removing and inserting the flex cable. I made my tool out of a picece of 0.006 inch thick spring stainless steel. I cut one end so it is the proper width for doing HP97 reader cables and the other for doing print head cables.
The delamination of the reader cable is a VERY common problem. I never unplug my cables unless I absolutley must do it. I have fixed some of the cables using IC2000 tire cement (black rubberized super glue used to glue RC model race car tires onto their hubs). The more tracks that have popped loose, the less satisfactory the experience.
I also fixed one unit that was missing a cable by removing the connectors and soldering in a piece of ribbon cable.
▼
Posts: 521
Threads: 72
Joined: Jul 2007
On my cable, _all_ of the contacts have delaminated.
Soldering a ribbon cable sounds like an easy fix...if I used a long enough cable, future card reader repairs shouldn't be hard.
▼
Posts: 1,788
Threads: 36
Joined: Aug 2007
If I have to do it over again, I think I will go down to the local surplus store and try and find some ribbon cable connectors of suitible size. If they are standard dual row, you can always cut off one row of pins. I think the hard part would be clearances with the case.
Before you go soldering, etc it may be worth trying to glue down the conductors. I have also though of using RTV. A very thin layer, cover the exposed conductor end with teflon sheet, and clamp gently in a vise until set. Hopefully the glue wont ooze all over the conductors.
▼
Posts: 521
Threads: 72
Joined: Jul 2007
The cable's useless as is, so I have nothing to lose by trying to repair it.
A hardware friend thinks I can probably get a replacement cable from DigiKey, but I need to know exactly what to order-- they don't have pictures (with tens of thousands of components, how could they?)
Case clearance shouldn't be a problem-- it can be folded, after all!
▼
Posts: 909
Threads: 40
Joined: Jan 1970
It shouldn't be hard to specify the cable. It is a standard pitch, 0.1", and has 13 conductors. Just measure the total length and make sure you get something at least that long - I measure 2.75". It might be possible to get them in different "phases" by which I mean whether the stripped part is on the same side at both ends, but I don't think so. The two outer layers are different, the thicker and tougher side isn't meant to be stripped - notice how it is flat and the other side follows the contours of the conductors. I've seen applications where the stripped portion of the cable is folded over to put the exposed conductors on the other side.
Now that I've measured the cable, I'll post the dimensions as a response to Renato, he said he saw some cable assemblies in a shop.
The only thing I find in the DigiKey online catalog is 500 foot rolls of 0.1" flat flex cable, on the first page of these two (I'd like to know the proper way to strip the cable - I think a vendor once told me they use something like a grinder or a wire brush):
http://dkc3.digikey.com/pdf/T032/0041-0042.pdf
On the second page they have prepared cable assemblies but only in 0.5 mm and 1 mm pitches. These might work via redundancy, like zebra strips, except the widest they have is 31.15 mm (30 conductor, 1 mm pitch). The first page shows the overall width of 13 conductor, 0.1" pitch is 1.4" or 35.56 mm. You might have success with two 36 conductor, 0.5 mm pitch cables (18.5 mm wide overall), letting them overlap a little in the middle - or trimming the extra insulation on the inside edges - with two equal width cables, and an odd number of "destination conductors", the gap in the middle falls right on conductor #7. 0.5 mm pitch has 5 conductors in the space of 1 in a 0.1" pitch cable, so it might work.
I tried one more thing on the DigiKey website - I did a keyword search for "flat flex cable". The search results were divided into categories, I chose " Cable Assemblies -
Flat Flex(1194 items) ". That took me to a page with a sort of nomograph - you choose " Contact Termination "," Length "," Number of Contacts " and " Pitch ". For Termination I chose " Solder Tab/Solder Tab " which I assume means just stripped ends [turns out I was wrong - see below]. For length I chose 3", for number of contacts 13. For pitch, the only choices were 0.05" and 0.1", which I chose. Then I clicked on "Apply Filters". It came back with a part number, A9AAT-1303F-ND, and a price, $2.52 for one piece. It also said " Quantity Available 0 - Value Added Item " which tells me DigiKey will make it (or have it made) to order. Electronics parts dealers love this kind of thing - since years ago when TV's and radios were repaired, and a parts shop could build you a potentiometer with switch, multiple sections, etc.
I can't give you a link to the final page, you'll have to start here and make the same choices:
http://www.digikey.com/Scripts/US/DKSUS.dll?KeyWordSearch
Make sure you don't click on " Items in Stock " on that page!
OOPS! They had highlighting on that part number, it took me to a catalog page - these aren't just plain stripped ends, they have flat terminals crimped onto the ends which are about the size of DIP IC pins. Here is that page:
http://dkc3.digikey.com/PDF/T032/0039.pdf
I've seen these before - Tandy used a long one about 1" wide to carry some signals across a board but I can't remember exactly what product it was. But I think this kind of termination is supposed to be an improvement over the stripped ends, because it doesn't have the problems of delamination and "smiling" sockets. They are made to plug into a SIP (Single Inline Plug) socket - like what resistor packs plug into for SCSI termination. They might mate with the existing sockets in the calculators.
I tried some other paths from the "flat flex cable" search results - I zeroed in on the 0.5 mm and 1 mm cable assemblies and the 500 ft roll of 0.1" cable.
Here's an idea - order the terminated cable (maybe a little longer, like 4", in case you try my final idea). If you don't like the way it fits in the existing sockets, you could get some SIP sockets (or cut a DIP socket in half) or you could cut off the ends and try your hand at stripping the insulation from the ends. The more I look at the cable from my 97, I think a Dremel with the 1" diameter wire brush would probably strip it pretty well (bristles moving toward the cable end). I would try to keep the brush just over the conductors and not try to remove the insulation between the conductors.
▼
Posts: 521
Threads: 72
Joined: Jul 2007
Ellis,
Thanks for that enormously informative message!
Posts: 1,788
Threads: 36
Joined: Aug 2007
I think you can just cram those crimped on pins into the HP sockets. I found a long 8 conductor at a surplus store and tried it a while back. The pins seemed to hold just fine. Certainly is worth a try.
BTW, I have two SR-60 calculators with serial numbers around 100 apart. One has the bare flat flex cables inside, the later one has the pin style. The bare cables have problems staying put, etc.
▼
Posts: 521
Threads: 72
Joined: Jul 2007
Hmmm..lemme know if you want to get rid of one of those SR-60s...
In the meantime I'll continue looking for a replacement for the cable.
▼
Posts: 1,788
Threads: 36
Joined: Aug 2007
Alas, one of the SR-60 machines is well and truly dead. And the CPU board is not the same. Even though most of the parts are socketed (!) most of the custom chips are different so swapping parts does not help much. Rather strange in a machine that had a production run of probably less than 500 units.
Posts: 1,162
Threads: 26
Joined: Aug 2005
My HP97 came in a pretty beat-up state, and my aim was to get a working machine, rather than one that was 'perfect'.
Of couese the reader cable was dead. What I did was desolder the connectors from the logic board and reader and replace them with 13 pin (I think) right-angle pin headers. I then used a piece of 26 way IDC cable and a couple of 2*13 pin IDC sockets to make a replacement cable -- of course I had to thread the cable through the chassis plaate before I crimnped one of the connectors to it.
I also had to be careful that I used the right row of holes in each connector (using the wrong one would have made no connections, of course. Works fine, even if it's not as HP did it.
Posts: 909
Threads: 40
Joined: Jan 1970
Quote: If I have to do it over again, I think I will go down to the local surplus store and try and find some ribbon cable connectors of suitible size. If they are standard dual row, you can always cut off one row of pins. I think the hard part would be clearances with the case.
Yes, that opening in the middle plastic is a big limitation on what connectors you can use. There's no way a dual row plug will fit through it. The red (or white - means made in Japan - 2.5mm instead of .1") Molex connectors for single wires are too thick also. The black connectors that you see in generic PC cases for the wires from the front panel that plug into the motherboard will fit through the opening. Molex C-Grid is one brand but I think AMP made them first.
I've studied this a lot (but haven't actually implemented any new ideas yet) but my favorite idea is using strips of screw-machine IC socket contacts with .020" diameter solder tails, which mate perfectly with their own sockets. I'm going to do this but right now I only have a 24 pin socket so I can only make two 12 pin strips. But starting with a 28 pin DIP socket, I will cut it in half ad cut off one pin from each half - or find two 13 pin single row strips - and solder one into the main circuit board (bent to a right angle) as a socket, and connect the other one to the card reader as a plug with 13 wires.
▼
Posts: 521
Threads: 72
Joined: Jul 2007
Quote:
Yes, that opening in the middle plastic is a big limitation on what connectors you can use. There's no way a dual row plug will fit through it. The red (or white - means made in Japan - 2.5mm instead of .1") Molex connectors for single wires are too thick also. The black connectors that you see in generic PC cases for the wires from the front panel that plug into the motherboard will fit through the opening. Molex C-Grid is one brand but I think AMP made them first.
Well, heck, it's just a slot in a piece of plastic. A little Dremel work is all that's needed...
▼
Posts: 909
Threads: 40
Joined: Jan 1970
Speaking of Dremel work - if I'm right, and a Dremel wire brush will strip flat flex cable - I can make 2181 of these cables from a 500 foot roll which costs $465 so my material cost per unit would be $0.213 - I wonder how many I could sell?
▼
Posts: 521
Threads: 72
Joined: Jul 2007
Quote:
Speaking of Dremel work - if I'm right, and a Dremel wire brush will strip flat flex cable - I can make 2181 of these cables from a 500 foot roll which costs $465 so my material cost per unit would be $0.213 - I wonder how many I could sell?
Heck, I'd buy 5 of 'em at $10/each!
I think I'd try a razor blade, myself, rather than a Dremel tool (to strip the cable)...
▼
Posts: 909
Threads: 40
Joined: Jan 1970
Only thing about the bulk flat flex cable and the terminated assemblies with 0.1" pitch - according to the descriptions the copper conductors are not tin plated. The metric cable assemblies (without pins crimped on them) are tin plated.
Posts: 1,788
Threads: 36
Joined: Aug 2007
Ellis,
Try Tanner Electronics in Carrolton. He has (had?) lots of single row screw machine pin sockets up to at least 20 pins.
|