HP48GX screen replacement



#11

Hi, I have a 1993 HP-48GX in the special edition made for ASEE and the calculator works, but the display is almost completely black. I want to replace the display and read that some of the screens from later edition HP 38G, 49G and 49G+ would serve as donors. Is that correct? I am interested in the black version of the display, which came on late production HP-48GX units.

Thanks,

Francisco


#12

I installed a screen from a 39G and I would expect the screen from the 49G would work as well. The 39G+ or 49G+ and later will not work.

Have you been inside a 48 before? The circuit board is pressed down against the display in a metal frame by 6 "twisties" that if you are not careful will break off. When you put in the new display you need to get it aligned right to do this I used clamps to hold it all together until I was sure it was right before resetting the twisties. Bruce Larrabee, who fixes calculators made up a special jig for doing this. IF you break one off I had some success soldering in a tiny brass screw in place of the twisty and then putting a nut and washer on top of the board, but you need to file a notch into the steel frame so that the head of the screw is flush or below the frame or else the board will not sit correctly on the frame.


#13

Quote:
I installed a screen from a 39G and I would expect the screen from the 49G would work as well. The 39G+ or 49G+ and later will not work.

Have you been inside a 48 before? The circuit board is pressed down against the display in a metal frame by 6 "twisties" that if you are not careful will break off. When you put in the new display you need to get it aligned right to do this I used clamps to hold it all together until I was sure it was right before resetting the twisties. Bruce Larrabee, who fixes calculators made up a special jig for doing this. IF you break one off I had some success soldering in a tiny brass screw in place of the twisty and then putting a nut and washer on top of the board, but you need to file a notch into the steel frame so that the head of the screw is flush or below the frame or else the board will not sit correctly on the frame.


This link might help: http://users.ju.edu/hduong/open/


http://users.ju.edu/hduong/repair/


Edited: 1 Oct 2013, 8:58 a.m.

#14

Quote:
the calculator works, but the display is almost completely black.
Only to be sure: Did you try adjusting the contrast setting (ON+Plus or ON +Minus) , or has the LCD bleeded out?

However if it's the ASEE version and you would like to replace the LCD without damaging the case, I'd recommend asking for help at one of the companies or people who have done this before.

I recommend the above because one who has never opened a 48 case before will very likely apply some damage to the case while trying, so it'd be better trying with an already damaged unit;-)


HTH

Ray


#15

Hi, the issue is not contrast, most likely a bleed. What are the recommended service providers? I e-mail FixThatCalc but they have not reply to my e-mail as of yet.

Thanks,

Francisco


#16

You might try http://www.vintagecalculatorrepair.com

#17

This is how the screen looks off:

An this is how it looks on:


#18

i believe it is a failure in the adhesive holding the polarizing layer in place, not within the glass envelope of the screen itself. this is a problem that the 95LX and 100/200LX palmtops suffered from too, almost exclusively in regions with high humidity such as singapore.

the screen may give off a slightly unpleasant odour too.

not that this helps you too much - the standard solutions still involve disassembly, and either replacing the screen or peeling off the polarizing layer (which you then clean the adhesive from and reattach in some way).

as an experiment, you could try placing the calculator (with batteries removed) in a WARM oven for a few hours and see if there is any improvement. try around 70 to 80 degrees celsius (160 to 180 degrees fahrenheit). the theory being to drive out any moisture from said adhesive.

DO NOT do what someone once did, when they set their oven to what they thought was 180 degrees F, and it turned out to be 180 degrees C. in that case their 100LX (that had got water inside, as i recall) came out as a lump of melted plastic.


cheers,
rob :-)


#19

I live in Puerto Rico and it is very hot and humid here. In addition to what can be seen in the pictures it also have bad lines (see image below), so will need a new display anyway.




Edited: 2 Oct 2013, 1:38 p.m.


#20

I sent today the calculator to fixthatcalc.com for repair; $70 and it will get the newer black display.

Edited: 3 Oct 2013, 9:18 p.m.


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