The Museum of HP Calculators

HP Forum Archive 12

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Some solutions
Message #1 Posted by Michel Beaulieu on 9 Apr 2003, 6:58 p.m.

I have a lot of these cable repaired in my TI collection : Just use an hair dryer to heat the contact area and slide a finger all over the glued area when hot; the result is great.

If one time is not enought, just do it 2 or 3 more time!

If not enought use WITH CARE a clean soldering iron on the cable and pass it all the way on the contacts area

If not enought, last chance, remove the cable from the LCD, cut some millimeters of the end of the cable and "glue" it with heat on the LCD with a "fer a repasser" (sorry i don'T know the english work for that thing we ues to remove fold on clothes...)

It shoud work!

You guys are crazy.
Message #2 Posted by Jeremy on 9 Apr 2003, 9:23 p.m.,
in response to message #1 by Michel Beaulieu

(with all due respect of course)

TIs are made to be disposable and cheap. As such, I would almost bet money that if you wrote a friendly letter and enclosed it with the calculator in a package to TI, they would simply send your son a new one. The letter should say something to the effect of:

"We have always had great success with TI calculators, and for some reason, a couple segments of the LCD just went bad... I know it is out of warranty, but I'm hoping you can do something for my high-school son."

If they sell in Wal*Mart for $12 or $18, they cost TI about $0.90. In the interest of keeping your business, they would probably just send you a new one.

Now if it a matter of pride in being able to repair the calculator, that is another thing. Along that line, the advice already given sounds good enough. ;)


PS - You'd be surprised at what a well-worded and polite letter to the right person can do for you. Maybe even if your son handwrote it, it would have a better effect. I know for a fact that TI has a vested interest in keeping high school students happy with their products...

Re: You guys are crazy.
Message #3 Posted by Michel Beaulieu on 9 Apr 2003, 10:02 p.m.,
in response to message #2 by Jeremy

It's true for a TI-30 x ir newer one but i repaired a TI-67 Galaxy programmable calculator with heat; this calculator is very rare and repairable. I slso did it with older TI models for collection purpose of obsolete rare items...

Re: Thanks For All!
Message #4 Posted by Paul Brogger on 10 Apr 2003, 9:34 a.m.,
in response to message #1 by Michel Beaulieu

Right, the thing isn't "worth" bothering with.

But if I'm successful, I'll get a weird sense of satisfaction completely out of proportion to the objective significance of the accomplishment. I'm sure it's a psychological flaw or deviant obsession, but there's a small increment of self-reliance to be obtained from fixing a "disposable" product. I guess I'm maintaining hope for servicability in a throw-away world.

This was $5 as the thrift store, but I didn't check it out carefully enough. I'm not trying to rescue $5 so much as exert a degree of mastery over my physical surroundings.

There are any number of superior products available. The older son (a high school senior, doing VERY well) is taking good care of his 48G+ after losing an HP-22s and flexing a -28s to death. The child in question (who represents a dicier proposition in many ways) just lost his second HP-30S, which had been covered with purple Marks-a-Lot along the way -- kind of taking the decorate-your-calculator-with-a-color-changing-faceplate idea to the next level . . . I'm a bit wary of putting too much into replacements for the middle-schooler just yet.

Thanks for the "heat & press" idea, and for the explanation of the probable mechanism employed.

I've already tried to build up the center of a "pressure ridge" that runs across the inside back plate and which seems to be meant to do exactly what I need done -- that hasn't worked, but I'll try some stiffer stuff.

The "return for a replacement" idea occurred to me, and I always have that as a last resort.

As always, a fine array of responses to an off-the-wall inquiry! Thanks again!

Re: Thanks For All!
Message #5 Posted by Ron Ross on 10 Apr 2003, 10:16 a.m.,
in response to message #4 by Paul Brogger

You might also consider an Hp6s for such a child. It is a piece of Crap, but it is an extremely durable piece of crap. It is small, made with an aluminum housing and my girl beat the stuffing out of it in her back pack for two years until upgrading to a graphics.

It is also CHEAP in cost if you can find it.

Re: HP-6s Crap
Message #6 Posted by Paul Brogger on 10 Apr 2003, 10:46 a.m.,
in response to message #5 by Ron Ross

Yes, the 6s is crap.

Or was, in my case.

The unit I bought was SO unreliable, with bouncy keys and missed keystrokes that (as I've reported proudly in the past) in a fit of pique, I threw it forcefully at the trash can, and have not regretted the action for one second.

I'll take just about any TI over an HP-6s (at least, one like the unit that I encountered) on any day of any week.

Crap, indeed!

Re: Heat & Pressure Worked Great!
Message #7 Posted by Paul Brogger on 10 Apr 2003, 1:44 p.m.,
in response to message #1 by Michel Beaulieu

I set the opened calculator on a metal lamp shade with the offending area of the connector in direct contact with the heat.

It didn't work the first time.

I set it back on, then went to the auto parts store and bought a Permatex "Rear Window Defogger Repair Kit", containing a tiny bottle of conductive copper paint. (Maybe someone would like to comment on whether I was on a right track?)

But when I got back, the calculator was fine! It's back together and destined for my son's backpack (and a lot more abuse!)

Thanks for the help!

Re: Heat & Pressure Worked Great!
Message #8 Posted by Ellis Easley on 12 Apr 2003, 10:42 a.m.,
in response to message #7 by Paul Brogger

I think that kind of conductive paint provides conductivity in both the "through" and "across" dimensions, as it will have to carry a hefty current for a 12V heating element. Probably contains a high proportion of copper particles that all draw together when the paint carrier dries. The conductive adhesive that I have read about contains a small proportion of tin particles suspended in an gummy acrylic material (like self adhesive stickers) such that only an occasional particle will find itself in contact with both surfaces on either side of the adhesive. It is intended for the tiny currents required by LCDs and keypads, etc.

I'm glad to know about the heat method! I wonder if the "fer a repasser" is an iron for clothes? (fer : ferrous)

Re: Heat & Pressure Worked (not so) Great!
Message #9 Posted by Paul Brogger on 12 Apr 2003, 2:34 p.m.,
in response to message #8 by Ellis Easley

You're exactly right about the Permatex defroster-fixer -- it's a copper suspension that needs vigorous shaking and dries really fast. But I wasn't going to use it as glue -- I wanted to paint new, individual connections between each PCB pad and its respective conductive trace on the flex connector.

And, it worked Great! (That is, as great as heat & pressure did, but the crucial "Middle Schooler Acceptance Test" is still pending . . . ) I got an art brush and painted short coppery lines from each PCB pad, up to and over each black line on the flex connector.

On the off chance that the flex was a sandwich, and covered with a clear insulator, I cut a couple of small, longitudinal slices into the end of each flex conductor trace before painting. I didn't do 'em all -- just the ones in the problem area. And the thing works fine, for now. (By the way, the brush cleaned up nicely with the first thing I tried -- isopropyl alcohol.)

The heat & pressure approach didn't withstand the rigors of young teenage life -- after one day in the backpack, the calculator had relapsed.

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