OT - Dot Matrix Display



#2

Has anyone ever had consistent problems with dot matrix display on calculators after not using the calculator for several months. I never have problems with HP or Casio calculators, however, several of my sharp and TI calculators; after being stored away for several months, I take them out to play with them again the some of the displays will have missing rows and columns of pixels. Typically I have to use them daily for a couple of weeks and the displays slowly come back. However, on some the displays just gets worst.

This has happened with the following models
sharp pc 1350
sharp el-9000
sharp el-9900
Radio Shack ec-4033
And several low end TI models, like the TI-25 and TI-35/36

Osvaldo Rodriguez


#3

I have a Sharp EL-9000 from 1988 that I use only rarely. All the pixels work and I have never observed a problem with them.

#4

Hi Osvaldo.

I have a Sharp PC-1401 since my college days (a dozen years ago - sigh!)

and all the rows and columns of pixels seem to work fine, but the "edge"

of each square pixel seems not to be that "sharp" (no pun intended).

It is as the pixels started to "wear out".....

Hope this helps.

Best regards.

Giancarlo


#5

Wow! I too used a PC-1401 as a calculation companion during my high school (final years of the liceo scientifico) and the first years of my Civil Engineering years (the most involved with math). It still works perfectly, and it's one the non-HP calculators I use more.

Think: I tried to substitute it with a Sharp PC-E500 during my job first year, but its gum keys tended not to respond correctly, so I reverted to my (limited) PC-1401, which has a fine keyboard, though not comparable to the one of my HP-15C.

I used to keep the 1401 full of BASIC programs, which performed quite everything, from beam calculation to easter day determination, from statistical (short) programs to the calculation of stars magnitudo.

Once I bought the HP-32SII in 1998, it fell into oblivion, for a while, until I discovered the programs got lost because batteries ran out. No leaking, though, so it's perfect still today.

I've got a little nostalgia for old BASIC calculators: they were both calculators and small computers.

-- Antonio

P.S. can you report its Serial Number, and the year you bought it, if you remember?


#6

Ciao Antonio.

My PC-1401's serial number is: 57049935

I purchased it around 1987 (more or less - can't remember exactly...) and it always worked flawlessly :-)

I too used to keep all sort of programs stuffed in it; I can still remember an amazing BASIC program

that I regularly used for drawing Bode diagrams - a great help during the exam :-)

It still works perfectly, except for that strange "wear" of the pixels edge...

Did you ever notice the ""hissing" the 1401 was used to do when doing some long and hard calculation or program?

It could be heard just by putting the back of the calc close to the ear....

Best regards.

Giancarlo


#7

Giancarlo wrote:

Quote:
Did you ever notice the ""hissing" the 1401 was used to do when doing some long and hard calculation or program?

No. To tell the truth, this is the first time I hear news about buzzes and hisses of the 1401 during (long) program executions. My unit works in perfect silence (of course, I may report a different thing in a few days - Murphy's law!)

Thanks for your data. I'll use them to retrieve the year when I bought it circa, since I forgot completely.

-- Antonio

#8

Quote:
Did you ever notice the ""hissing" the 1401 was used to do when doing some long and hard calculation or program?

My HP-41CX used to do that, too. No sound when the machine was off, a very faint noise when it was on but idle, and a kind of "hissing" when it was running a program.

- Thomas


#9

Quote:
My HP-41CX used to do that, too. No sound when the machine was off, a very faint noise when it was on but idle, and a kind of "hissing" when it was running a program.

That's the fan. It kicks in when the CPU is under load. My notebook does the same. The 41CX is an incredible machine.

:-)

#10

I've heard that tin whiskers are a problem with aging electronics. The leads of components on a circuit board get shorted by microscopic crystalline tin growths.

I think there was even something recently on the Discovery Channel here in the US about this phenomena. From what I understand, the conditions in which these occur aren't understood, but everything from satellites to calculators have succumb to its effects.

Given that what you're seeing develops over time, it would seem possible tin whiskers might be at fault.

NASA's Tin Whisker Page

-Dan


#11

Dan:

Very interesting reading. One of the articles is from HP, apparently they have a program where they train engineers to test for and identify whisker formation in electronics. Furthermore one of the articles mentioned in some situations low currents, those less than 10 mA can lead to permanent shorts, however, if you pass currents greater than 10 mA it may be able to melt the whisker and resume seminormal contact. As I mentioned, for some of the calculators, they problem begins to go away the more I use them. I'll keep reading.

Thanks

Osvaldo


#12

The first I'd heard of whiskers was in regard to the raised-floor tiles where I work. I was surprised that we contracted a firm to come in periodically, take out the tiles and clean them and the floor underneath. I asked why only to be told about zinc whiskers which grow on the tiles and when broken off can get ingested by air-cooled equipment. The effect is similar to tin whiskers but the source is air-borne instead of growth from within.

NASA's Other Metal Whiskers Site

Regarding the higher current remedy for tin whiskers, we're probably doomed there with LCD displays consuming mere micro or even nano-amps. Older calculators with LED displays would likely consume >10mA but that may be confined to the display circuit leaving the rest vulnerable.

-Dan

#13

Quote:
I've heard that tin whiskers are a problem with aging electronics. The leads of components on a circuit board get shorted by microscopic crystalline tin growths.

Tin whiskers are only a problem with the new lead-free solders. I have two HP-71's from 20 years ago that have never had a problem of any kind.

#14

Garth,

That's interesting. So when gaining RoHS certification (by being lead-free) components are now more vulnerable to tin whiskers.

Everything is a trade-off.

-Dan


#15

Our company has been watching this RoHS garbage carefully. So far our markets have not required us to go RoHS, but I've collected and read a lot of articles because I suspect we will have to convert at some point. We would just rather let other companies be the guinea pigs and get the problems figured out before we get into it.

There are a lot of disadvantages to lead-free besides tin whiskers, such as that lead-free solder does not wet as well, requires higher soldering temperatures that cause other problems, and it cracks a lot more easily. All of this, I believe, for nothing. I grew up in another country and all our drinking water came to us in lead pipes, and yet a high percentage of the kids in the grade school I went to became doctors and engineers. So did all that lead hurt our brains? Near me now is a local land fill with decades of electronics waste in it, and the water company sends a report on the ground water quality every year along with the water bill. The quantity of lead in it is about one-eighth as high as it would need to be to take action, and the suspected source is "erosion of natural deposits," not the landfill.

#16

Quote:
I've heard that tin whiskers are a problem with aging electronics. ...
-Dan

My understanding is that the Lead (pb) in solder prevents these tin whiskers, and that recent environmental laws have banned lead, so this should not be a problem with most things created before the laws if they are using tin/lead solder.

#17

I beginning to think if it is environmental. At first it only happened with the very low end TI's the TI-25 (which is a solar calculator) used to be like $12 or less 10 years ago, but in the last couple of years it began with the sharp models. At first I tried to search on the net and did not find anything about this. I do have to say this though I do use my calculators, thus they do take a beating sometimes since I carry them with books and do leave my bag inside my car at times. Summers in west Texas can be upwards of 100 F. I should begin to pay closer attention.

Osvaldo Rodriguez

#18

I've seen it and heard about it. From anecdotal evidence my understanding is that the typical cause is environmental stress (shock and temperature extremes). As I recall pulling the batteries and installing them again will often spontaneously resolve the problem. What conditions are these machines being stored in?


#19

My first and only AOS calc was A Casio progamable, f 602p. It was easy to prg but the keys were soft- no feed back and working complicated formulae was not easy. It has a nice dot matrix display which never degraded and something Ive never seen on a calculator- it has both upper and lower case letters! It still works as does its printer Howard


#20

I don't know if the 48G series and later graphing calculators count, but they do both lower and upper case letters... even (some) Greek letters, but only lower case; I'm not sure I've seen capital Greek letters on them.


#21

A comprehensive display of the characters that the HP48G and its successors can display is shown by pressing <RS> <CHARS>. These include numerous lower case Greek characters, and the upper case sigma, pi, and omega. Of course, a number of the other upper case Greek letters are the same as their English (or Latin) counterparts.


#22

Oh yes, you are right! I haven't programmed my 48G's and 49G+ so long I forgot! It's almost as good, if I now recall properly, as the character tables in Windows or ANSI keyboard codes in a word processor!

Kudos to HP for including them in the 48's and 49's.

#23

Hmmm... earliest HP calculator with lowercase letters in the display? I'm not going to count the 41C, which only has lowercase a through e... I think it would be the 28C, which was introduced 3 years after the Casio FX-602P. Can't win 'em all. :-)

- Thomas


#24

Quote:
Hmmm... earliest HP calculator with lowercase letters in the display? I'm not going to count the 41C, which only has lowercase a through e...

Well, halfnut 41C* indeed had all the lowercase characters (ugly as some of them look)... just hard to show on the display ;)

You can try Angel Martin's Sandbox ROM to use them.

Greetings,
Massimo


#25

Quote:
Well, halfnut 41C* indeed had all the lowercase characters (ugly as some of them look)... just hard to show on the display ;)

Really? I didn't know that... I used to own a 41C, and later a 41CX, both of which I bought within months after they were introduced; both fullnuts... I didn't get into synthetic programming until after switching from the 41C to the 41CX, but on the CX, as I recall, character codes 102 through 122 all displayed asterisks. Do you know if there are any screen shots online that show those other lowercase letters?

Dang, maybe I should get a 41C again. It would be almost like owning an original VW Beetle. Ah, nostalgia. :-)

- Thomas


#26

Hi Thomas,
Screenshots from V41 and Sandbox ROM:





You get the idea...

Not so useful per se since you have no way to use them from the basic hardware, but they are there nonetheless.

Greetings,
Massimo


#27

Hi Massimo,

Thank you for those screen shots! I think those letters look pretty decent, actually. I'm not sure I understand what you were saying about the Sandbox ROM, though; does that ROM somehow override the 41C's built-in character definitions? In other words, if I do 102 XTOA on a halfnut, will I only see the lowercase f if I have that ROM installed, and the usual asterisk otherwise?

Best regards,

- Thomas


#28

Quote:
In other words, if I do 102 XTOA on a halfnut, will I only see the lowercase f if I have that ROM installed, and the usual asterisk otherwise?

No, you will see the usual boxed star. To access the extended character set you have to enable it.
More info on Ken Emery's HP-41 MCode for Beginners (also available on the Museum's DVD set) from page 107.

I'm sure I once found and printed some additional documentation but I am currently unable to find it.

HTH,
Massimo

Edited: 3 Sept 2007, 1:17 p.m.


#29

Quote:
To access the extended character set you have to enable it.


More info on Ken Emery's HP-41 MCode for Beginners (also available on the Museum's DVD set)

Thank you for the info! I guess this means I need to upgrade my Museum DVD...

- Thomas

#30

I must admit that I became a collector by accident. By the time I realized I had a few calculators piled up in different places. They have been stored in plastic containers placed in a closet. Dark, mostly dry place. The temperatures may get high during the summer, but not above mid 80's. As I mentioned before, it always happens from lack of use, and I have had it happened in older calcs, as well as new ones. The sharp EL-9900, is only about two years old. I had not used it in over a year. I pulled it out a couple of weeks ago and as soon as I placed batteries I noticed missing pixel lines both vertical and horizontal. I have been using it for the last two weeks and with the exception of two vertical lines, the other have "fixed" themselves.

Osvaldo

#31

I would expect "natural corrosion" as the main cause. If the connection isn't soldered, humidity and H2S or SO2 will do their work and create a thin layer of non-conductive stuff on the contacts. Disassembling the unit and cleaning the contacts (mostly flex strips) will probably help.


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