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Recently I've got a 1984 USA 15C in very good cosmetic condition. Also it passes both self tests.

The problem is that when the number in the screen has more than seven numbers, the "ink" is weaker. If I delete some numbers, the presentation is normal again...

Curious: the "8,8,8,8,8,8,8,8,8,8" screen of the self test is perfect!

Ideas?

Raul

Try new batteries. Next try to tighten the screws just a tad to get better pressure on the contacts. Else total dissassembly and clean contacts between LCD and board. Last option is not really advised. I really suspect a new set of batteries will solve your problem.

Thanks Ron, but these batteries are new and make work perfectly other 15C... :-((

It is opened: I need info for taking apart the board...

Hi Raul,

there were some descriptions round here,
but I don't have the links.

To take out the board, you'll have to cut the heat stakes.
For just re-aligning the display,
it could be sufficient to cut all stakes BUT the bottom row.
In other words, you could let the bottom row of stakes be there, so the PCB will not be too loose after closing the case. You can move the PCB out to an angle, and then take out or just re-align the display block.
Of course the above description only applies to the single-PCB variant of the calc. Older ones have a separate LCD housing,
so disassembling may be easier there.

Regards,

Raymond

Could you explain what is exactly "the heat stakes"? Do you mean the four rows of "brown things"?

Thanks Raymond

Hello, Raul; I'm sorry I was not here sooner. Daily affairs (it's about 1:00 PM in Brazil, now, and I usually access this forum for longer sessions at night, seldom during the day)

Let's see: you have dim (fading) numbers when entering the last ones, but have you observed the same fading effect when seeing the -8,8,8,8,8,8,8,8,8, "selftest O.K." display?

Also, have a look here:

and

These images are from the first Voyagers type. This is, for me, the hardest one to "service" because you'll need to disassemble the "flex-LCD-IC's" assembly, and getting them back together is sort of a nightmare... unless you have pacience and adequate tools.

If yours is the one with a single PCB that goes front top to bottom, then you have to "cut" the top of the het-mldet revits; they are more than fourty black pins you find regularly spread over the PCB. The best way (and more time cnsuming) is carefuly cutting each oné's border, so you keep the top of the plastic to "melt" some of them them back and keep the mainboard in place again.

I'll wait for answer and get back later, O.K.? If yours is the one-piece PCB, you'll need to open it in order to clean the LCD's contacts, what demands disassembling it. Otherwise, if you heve the skills (I'm almost sure you havë), you can re-solder all terminals of the biggest IC, also known as R2D2 (not the Star Wars robot, the RAM/ROM Display Driver). Use a soldering iron with any wire connecting its metal parts to both (+) and (-) poles of the calculator, i.e., remove batteries and use a wire to connect them both to the soldering iron. This wil prevent ESD damage.

I'm getting back in a few hours.

Success.

Luiz C. Vieira - Brazil

If yours is the single PCB model you may have a real problem. Yes, you can cut the heat stakes and free the circuit board, but is it just about impossible to get it back together so that it feels the same. You will probably be happier living with a lower precision world.

No... no fading with the selftest screen but PI with FIX 8 is almost invisible...

And yes, the "ill" 15c is one with single PCB: i'll try to clean contacts but I can not resolder...
Thanks, Luiz

Raul

Hola, Raul;

I am not quite sure a single cleaning will solve the situation. Anyway, as you have all annunciators "lit" after the seftest, chances are their "state" help keeping the rest of the display readable. Try writing PI with a FIX 9 and keeop GRAD, USER and C (Complex Mode) ON, and check if low-end numbers are better to read. if so, a cleaning procedure is probably the best solution.

Success.

Luiz C. Vieira - Brazil

Hi Luiz:

The PCB is out... How to clean?
(Perhaps the comunication will be easier by email)

Raul

Hi, Raul;

you may be right, unless its stated that:

"Procedures below assume you are acquainted with the process; do not try it unless you have the skills or you may damage your calculator!"

It does not apply to you, Raul, of course. PLEASE, read everything first as many times as you think you need before trying. It's harmless if carefuly done.

The major concerns are:

1 - Electrostatic discharges; take your safety precautions
2 - the two small springs that connect both bezels to the back label
3 - keep track with removed parts and be aware of alignment, etc.

You see a metal frame around the LCD and it has four locking tabs on the top and another four on the bottom, and they lock the complete assy to the mainboard. You should carefully unfold (partially, not to straighten them) the tabs so you can remove the frame; keep the mainboard with the IC's on the top and the LCD on the bottom, for safety. Be carefull not to allow the LCD fall on teh floor and cracks...

After rmoving it, take the two polymers and carefully inspect them for dust and dirty particules. Clean it with the best cleaner you have (I use alchool and, while it's not yet dried, I remove the exccess). Look at both conductive surfaces and check with reflexive light so you can "see" if it is homogeneous. It's also a good practice to clean the LCD's contact surface where the polymers touch it.

Rebuilding it needs patience: replace the polymers in their original position (they do not have a left- or right- prefetrence alignment, just place them as they were before) and then it's time to "push" them back.

First try to insert the complete set at once, gently twistint the tabs so they will all be in place at the same time. If you do not succeed doin that (I seldom do), you insert the lower part first (wtih the holes in the mainboard) and then the upper part (that borders the mainboard). Before you lock the tabs back (gently folding them as they were), chaeck if the polimers are aligned with both the LCD and the contacts in the mainboard. If you "see" they are twisted, try to pull the LCD assy back a little enough the polymer realigns itself. If it is twisted, may some segments be off.

If you are sure the polymers are in place, fold the tabs back and replace the mainboard. Remember placing the (-) pole spring. Place the batteries and try the [ON]&[×] seftest and check if everything lits. If not, you may need to remove the LCD assy and check again for cleaning OR simply checking if the polkymers are not folded or twisted.

It's sometimes time demanding and tedious, but I have rebuilt all Voyagers of this type successfuly. I cannot say the same about the flex-circuit type.

If you are in doubt, don't do it. Try with a broken voyager first before doing. Anyway, you may succeed. I do!

Success!

luiz C. Vieira - Brazil

Hi Luiz:
First of all, THANKS.

Only a question: How to re-build the PCB in its original position now, with all "heat spots" cut?

Raul

Hi Raul,

that's why I suggested to leave the lower row of stakes in place;-)

However, you could use a hot glue device, I don't know the english word.
It's that kind of glue you often see in electronic devices to hold cables in place.

Regards,

Raymond

You mean hot melt glue gun. I reassembled my 15C using a tiny drop of time-thickened superglue on each post, one at a time, pressing the PCB to the case until the glue set for each drop. The result was good. If I ever need to do another (actually, I have a 12C that could use it) I'm going to build some kind of fixture to hold things together. Randy Sloyer (I think) posted a description of undoing the stakes with a hot tool - instead of cutting them off, he melted them and formed them back into cylindrical form so they can be re-staked. I'm going to try that if I have to start from scratch (my 12C is already cut apart). Does hot melt glue set up completely? The spring forces in the keyboard are always working against the glue, if it doesn't set up hard - if it has any "creep" - it will come loose in time. I have seen a high temperature hot melt glue that needs a different gun but I haven't tried it yet (too hot might be a catastrophe, it could melt the posts and they could separate from the case!).

Hi, Raul;

About the LCD: is it OK now? Didi you have any difficulties? It would be good mentioning any part of the process you felt as needing more advice.

I think that as we have more and more users able to accomplish this sort of task, we´ll have more and more calculators in condition to work.

Best regards.

Luiz C. Vieira - Brazil

Having experimented, let me say that I have NOT found a hot-melt glue that would not "give" too much for this application. If we were talking of larger surface areas, it might pass-- but the small stakes will inevitably pull through the glue, given time and use.

Cyanoacrylates ("superglues") are convenient to work with and will probably do a passable job IF you don't bang the calculator or keyboard much. Remember, these glues depend on surface-to-surface contact (not a lot of "gap-filling"), and they have enormous adhesive strength, but are awful as far as shearing, tending to be brittle. There are several formulations made, and a few of these would be preferred for plastics-- get one made specifically for that.

The BEST option, in my opinion, would be to start by trimming with an x-acto knife, the "doughnut" from around the post where the plastic was deformed. This would at least allow as much of the post to remain as possible. On restaking, while holding pressure on the board to keep it down, I'd use a conical-tip soldering iron and push it lightly halfway (not fully) into the stake. You want to drive some material out above the board, but not cut it off from the rest of the stake. After doing each point for the whole board, then testing that it still worked, I would think it best to reinforce the job by adding a small drop of two-part epoxy over the mushroomed area, enough to cover its top and the ring-interface of board-to-stake. (This "filling" of the donut hole just intended to reduce some stress on the melted "neck" area of the stake.)

A "shortcut" I used on a different heat-staked device, was to use a blade tip on a soldering iron, to "shape" the deformed plastic UPWARD, so that I had MORE post than I otherwise would have. This was terribly tricky, because in the process of removing the circuit board, it would not lift cleanly until I had reheated and pushed around little gnarlies from my reformation effort. I had another less serious (and heatless) battle putting the board snugly back in place-- but at least then the job of re-staking was just a matter of melting the crown back to a button with the flat blade of the solder iron. But this was so much of a job I would not recommend it unless you pretty well figure you shall have to open it up again at some point, and I don't figure you could do this operation too many times before the posts were just too fragile.

I have not the skills for doing the job so I have got only a puzzle :-((

Actually a pity: keyboard, bezel, logo... all in this calculator is in best condition than in the one I use. But screen.

Raul

I too use this method of restaking the cut heat stakes (i.e use fine solder iron tip) and it seems to work well. It is a one shot deal though. After re-staking with the solder iron I sometimes apply a small drop of epoxy but it may not really be neccesary unless someone presses real hard on the keys.
One small note about cleaning the LCD zebra connectors. Make sure you don't strech the connectors as you clean them with alcohol or contact cleaner. Just brush them lightly or they won't fit and will have to be retrimmed.

Hey, Raul;

Now I'm worried: what happened? You disassembled it and did not get success reassembling back? If I understand it well, you removed the screen bezel, too. If so, and your calculator is already assembled, you can gently, gently press the LCD borders while showning a 9-digits number (PI?) and see if it reades better.

If needed, I can scan (I have no photo camera) images of the itermediate parts of the LCD reassembling. I'd rather have a digital camera in hands, now...

Let me know what you want.

Luiz C. Vieira - Brazil

I like the idea of displacing some of the plastic from the post to make a new mushroom cap. For one thing, I can apply it to my 12C that already has the tops cut off! And applying the epoxy afterward can be done in a leisurely manner. One bit of advice from Randy's post that might apply is to use the minimum temperature required to melt the plastic. A small pointed soldering iron sounds like the ideal tool - the pointier, the better, I think, because it would go deeper into the post and so the remaining wall would be thicker for a given amount of plastic displaced to the top. But the normal temperature of a soldering iron would burn the plasic and ruin it for structural purposes. I asked Randy for a temperature and he tried to give an estimate but pointed out that the practical way would be to use a variac to slowly raise the voltage until it just melts the plastic. Since a lot of people don't have a variac, I imagine a lamp dimmer would be fine for a small resistive load like a soldering iron. The low temperature on a variable temperature soldering iron is probably still much too high for this purpose.

.

One other thought about re-heat staking - I'm thinking about mounting the soldering iron in a drill press so I can set the depth, hopefully I can do all (40? 44?) posts uniformly (hopefully not uniformly bad!)

If you build the right tool and can cut the top edges of the heat stakes, but leave their centers, it is possible to remelt them.

The glue that I have used is called IC1000 (or is it IC2000) tire cement made by Bob Smith Adhesives. It is a black rubberized super glue used my model car racers to hold on tires. Best thing around for rebuilding battery packs, etc. You can find it a many good hobby shops and Hobbytown. Sice it sets slowly in blob applications, I would use some accelerator fluid.

One thing to be aware of in superglues is that they will outgas a superglue fume cloud that could possible contaminate the keyboard key contact access holes. I would keep the machine under a fan for a day or two... othwerwise it may be teeny weenie wire brush in the keyboard holes time.