OT: LCD Repair Question



#2

Good morning,

since we had a thread on the Casio fx-190 (electronic ruler/scale) not long ago, I dare ask a question here that is related to this specific machine, but also applicable to HP calculators of course:

As you can see from this picture, my recently acquired fx-190 has a little problem in the LCD that generates the electronic scale:

For me, it is hard to tell wether the display itself is leaking, or some external fluid has penetrated between the display and the polarizer.
I am not really interested in calculators with LCDs (with some exceptions, like HP-71B and suchlikes and exotic calculators like this one here), so I never tried to repair a liquid crytal display.

My question would therefore be: Is it at all possible to repair defects like the one in the image above? I am a bit reluctant to take the calculator apart because it is in "like new" shape otherwise, and if the experts here tell me, that there is no chance of fixing it anyway, I will leave it as it is...

Spring Greetings, Max

NB: (Regarding the last fx-190 thread) I have the original manual (French/German) for this calculator in case there are questions left regarding the operating of the ruler or its (very exotic!) programming "language".


#3

The display is failing, the only way to repair is to replace with a good display from another unit.


#4

Randy,

What is the most likely cause of such a failure? I have a very nice (extremly good condition) HP42S (old style - which I prefer (mainly looks)) that has some of this encroaching into the display from the left side. The progress may have stopped or it is very slow as I have been using this calculator for about 3+ years since noticing this. It has not encroached into the readable part of the display yet but is very close. I guess it shouldn't bother me since I took steps years ago to assure that I would always have one of these (my most favorite) calculators, and I have two others of the same model in the same condition.

I really use it a lot (daily) both in and out of the office. I certainly cannot identify any action or notable abuse that would have started this cancer.

Also, how difficult is it to replace the display in one of these older model 42's? And,I am not talking from my standpoint but yours.


#5

Quote:
What is the most likely cause of such a failure?

The display in question, physical impact. It's just broken :(

I suspect most failures are caused by physical damage of one form or another. But, small blobs of black can be internal contamination from the manufacturing process that just take years to show up.

Replacing a display in an older Pioneer, the windowed type, is a real pain. The later open bezel models are much easier but overall, LCD replacements are one of the more difficult repairs, at least for the first ten or twenty times :^)


#6

I disagree. Most LCD-failures are *not* from impacts.
The two glass plates need to be sealed air tight - this seemed to be rather tricky "back in the days". I have a lot of LCD calculators dating back to the end of the 70s with this issue.
Funny sidenote: the first LCD machines done by Rockwell had a failure rate of nearly 100% - due to this issue.


#7

Hello!

Quote:
The two glass plates need to be sealed air tight - this seemed to be rather tricky "back in the days".

I case of my Casio Calculator above, I can't see any phyical damage like shattered glass, so I also suspect a breech in the bonding of the two glass plates. And there is enough "crystal fluid" remaining inside for the display to work perfectly to the left and right of the stains.
For me it would be enough, if I could seal the leak somehow to preserve the calculator in it's present state. Is there any type of sealant or glue that is recommended for this purpose?

Greetings, Max


#8

It cannot be repaired... only replaced.

Quote:
I disagree. Most LCD-failures are *not* from impacts

Whatever... so my boxful of dud HP LCD's with spider lines are not from impacts. Foolish me.

So you think a thin piece of glass that long and that narrow when subjected to a torsional force wouldn't be physically damaged at the glass to glass seal? Funny, it failed right in the middle too... oh well, wrong again.


#9

I suppose it depends on when they were manufactured, but I tend to agree with Frank and Maximilian that they have to be built with care, and perhaps the earliest LCD manufacturers just didn't realize how critical it was to have it all hermetically sealed.

We used to use a bunch of LCD displays in our radio astronomy research equipment, to show the LO frequency of a bunch (typically 14 per rack) of video converters, as well as some other housekeeping info (power levels, ...). We built several dozen of these racks in the late 70s/early 80s from high-quality commercial parts. By the 90s, many of the displays were no longer useful. This equipment was never beaten, dropped (the rack they were in weighed hundred of pounds!), jarred, etc. They just sat in a nice temperature-controlled room and they got the same black plague as seen here.

#10

Spider lines are the result of physical damage 8)
However this is not what we see here; the large LCD is impact protected and we would certainly have a trashed calculator if this would be the case. (Please also note the tinier black spot to the left...)
But you are right - this cannot be repaired and certainly gets worse over time.

#11

Randy,

In my case, I figured it might be cold (down to 10-degrees-F in a car overnight), heat (maybe up to 130+ in a car during the day), or up and down in an airplane a number of times. It seems like they grow in strange ways like some windshields will crack when hit or when stressed at the edge where some warping force is exerted by the fasteners.

Forrest

#12

Hallo Max,

Quote:
I have the original manual (French/German) for this calculator in case there are questions left regarding the operating of the ruler or its (very exotic!) programming "language".

I'd like to learn something about it. Do you have this manual scanned and are you willing to share it (at least the chapter about the ruler)?

#13

Hallo Walter,

Quote:
Do you have this manual scanned and are you willing to share it (at least the chapter about the ruler)?

I scanned it today (only the German part until now), you can download it from here:



http://www.bombie.de/forum/Manual_Casio_fx-190_D.pdf



I still wonder who was supposed to use this thing?

Greetings, Max


#14

Hallo Max,

thanks for the scan. I join you wondering about the target market for this device. May have been in the time when semilogarithmic grids on paper were expensive. Perhaps people who could't read a ruler? ;)


#15

Quote:
May have been in the time when semilogarithmic grids on paper were expensive.

My recollection is that log-log and semilog paper (high quality - printed by K&E) was never more than 10 cents/sheet. How many sheets would you have to save to pay for the calculator?! :)

#16

I don't think there was a target market (How many might they have sold? 5000pcs?, it was rather a demonstration of engineering skills. Remember the Calcu-Lighter, Calcu-Pen, LCD calculator with abacus. These type of "gadgets" started early in the 70s with Crown (Japan), combining desktop calculators with tape recorders, radios and so on. Rather pointless too 8)


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