Display in bad state on stored 48G

[schuh]

Hi all!

It has been about 20 years since I purchased my 48G.
I did upgrade to 128KB, plus 128KB+512KB of internal memory (poor work on the keyboard plate surface, I know it's ugly, but works!).

Yesterday my wife asked for a handheld calculator, then I offered my 48G.
It was stored in the original soft case.
Inside the case there was a small silica gel pack, and a couple of cardboards inside the internal pocket, to add extra protection for the display.
The case was inside a drawer in a wooden TV rack.
So, I thought it was pretty safe, and I just needed to install the batteries and turn it on, but as soon as I took it out of the case I realized I had a problem.

The display is in a very very bad state, which is weird. It looks like some sugar concentrated liquid was poured over and dried. The surface is rough.
Anyway I tested it, and it beeped, and the display seems to work, but the central area is barely readable (see attached pics).

Later yesterday I figured out what could have caused that.
The spot where the calculator was is exactly below the PS3 in the rack, and the console used to be powered on for several hours eventually, getting hot.
So, I suspect it's heat damage on the anti-glare surface of the display, which I suppose it's some plastic material, which melted by the continous heating, although probably not too high temperatures.
I still have to test playing some graphics intensive game to confirm what is the temperatures range it gets inside the drawer.

Anyone already saw something like that?
Any ideas on how to fix it, or at least improve display surface?
Maybe I'll have to replace the display, which seems to be a hard to find part.
I have seen old 48G/S/X on sale, but either they're functional or have damaged display (some seems to have the same display problem), not so useful for my needs.

Thanks for any help!

Cheers,
Saulo

   
   
   

[Jlouis]

Yes, I've seen it. Many times.

It's due to heat. I see you live in Brazil, like me. Depending on the city you live, the temperature can lead to damage the display, although HP specifies IIRC 40°C max temp, I've noticed that 35°C is enough, combined with humidity, to damage the display. Specially the black screen.

I think it is repairable. There's a gentleman in Curitiba that do this repair, see here.

You can substitute the display also. HP 49g, 39g, 40g can be donors, with the better contrast black screen.

Good luck!

Seja bem-vindo e um abraço do Rio de Janeiro

[cdmackay]

PS3 can get very hot. I have to run mine with the doors of my TV cabinet open, and nothing else near it to get melted.

[burkhard]

(03-20-2019 01:22 PM)Jlouis Wrote:  You can substitute the display also. HP 49g, 39g, 40g can be donors, with the better contrast black screen.

Yes, those models Jlouis lists can be had for cheap on the auction site. Right now I see a bunch of 39g for between $20-$30 including US shipping. Obviously that will be more to Brazil, but that will give you a general idea. Sometimes I see them unused, but without factory packaging out of China for very low cost including worldwide shipping.

If I needed to do a display repair on a 48 series, I would definitely use one of these models as a donor rather than another 48. These models are *cheap* and like the last years of the 48, use the black screen with much better contrast than the blue/green one you have.

Certainly put in a black screen. Now is your excuse!

[schuh]

Thanks all for the help up to here!

Yesterday I opened it again (it has been a while since last time, when performed the memory upgrade). I didn't get to the display yet, I plan to try working its surface, before to declare it needs replacement. I think would be happy if I could just remove the crap out of it, even losing the anti-glare feature.

If it's beyond repair, I'll have to find a replacement. However, it seems there's no display for sale anywhere. I use to buy parts for my projects from aliexpress, ebay and mercadolivre (our ebay equivalent in Brazil). But this display, even being a fit for several models, isn't available, which surprising to me, since display and keyboard are the parts more likely to get damaged! It seems HP doesn't want its calculators to be serviceable, and sadly no other manufacturer got attracted by this market.

I asked a couple of repair services here (one provided by Jlouis) if they have spare display for sale, but I doubt.

Also, it's a pitty I couldn't find any deffective compatible calculators, except display deffective. I'm personally against to jeopardize a working machine only to get a part, but it seems I may be out of options soon... hope not!

[franz.b]

I think that with a proper abrasive job the display will go back to being usable.

[burkhard]

(03-21-2019 02:23 PM)schuh Wrote:  Also, it's a pitty I couldn't find any deffective compatible calculators, except display deffective. I'm personally against to jeopardize a working machine only to get a part, but it seems I may be out of options soon... hope not!

I wouldn't think twice or feel bad about cannibalizing a 39g. This was a lame de-contented algebraic model produced for the educational market. They are (almost) a dime-a-dozen because few people want them and there seem to be a zillion produced for sale in Asia that are forever coming up for sale.

Let us know what you wind up doing and how it works out.
Good luck!

[schuh]

Well, it seems the procedure was a success at all!

I learned there're two layers of plastic over the LCD: one blueish, which was in the worst state, and a transparent and thicker bellow it, which had a cracked blister in the middle, so I had to remove it too.    

The procedure I used was based on some steps I found on google, for removing anti-glare cover from computer displays, which consists of keeping a wet paper towel over it for several hours, and then peeling it off. However, I'm not sure it was of any help, as it was pretty hard to peel it off anyway (and I don't think the glue is water based).

I started by removing from the cracked blister in the middle, and used a sharp knife to cut it at the edges (I couldn't remove the LCD from the metal frame, as I was afraid of breaking it putting too much force to pop it off). After removal was complete, I used a swab wet on paint remover against the remaining glue.

It took me a while to figure out the removed blue plastic was the polarizer. After putting the calculator back together and turn it on, I hear the beep, but couldn't see anything on display. Then I suspected I needed glasses to see the image, and bingo!
   
   
   

I was afraid the back surface was damaged too, but after removing the front plastic I could see it was intact.
So, I'm satisfied with the result, although not final yet, as I have to wait to receive the polarizer film I ordered.
It's a replacement for smartphone screen. I hope it's of the correct type.

[schuh]

Well, finally I've got the polarizer.
However, unfortunately it wasn't of the right type.

I ordered a replacement filter for the Samsung Galaxy S6, hoping it would fit.
There are two problems:
1. The angle which gives good image is 45º from the borders. So, there's no way I can fill entire screen, there are small uncovered triangles at two corners, which isn't that bad, considering the next problem.
2. The adhesive is in the wrong side for me. The side which gives the good results leaves the adhesive surface outwards, so I can't stick the filter to the screen, thus leaving space between them, producing shadows and weird colors. Also I can't remove the plastic cover which have a red line (that indicates the cover wasn't removed).

I'll have to investigate the exact specs of this polarizer to be able to order a different one.
Probably I'll have to try a number of different types, until I get the right one.

   

[burkhard]

(04-03-2019 03:02 AM)schuh Wrote:  I'll have to investigate the exact specs of this polarizer to be able to order a different one.
Probably I'll have to try a number of different types, until I get the right one.

Thanks for doing the legwork here and posting the steps... It will save some future souls a lot of effort.

[schuh]

Finally, yesterday I received the new polarizer.
This time I ordered the right type, a linear one.
With the linear I can find the right orientation with the adhesive side facing the display.
It's 10cm x 10cm. The display is about 6.4cm x 3.9cm.
So, it has enough material to twice tries, which was good, as it turned out to be not so simple to make straight cuts and produce exactly four right angles (one is for free, still have to do three). One of the main dificulties was to make the marks to guide the cut. Ballpoint pen isn't the proper way, but i don't have other type.

Yesterday the first try was a fail, so I decided to try again today, with daylight it's better to see
The final result was pretty fair in my oppinion. It's a little bit yellowish, but its much better now!
Now it can be used again!

   

Thanks for the messages and the help!

PS: The number in one of the images is the actual available memory, as I mentioned before, this calculator received a memory upgrade several years ago, and it has 128k of main memory, plus 128k of first bank attached, plus five 128k banks. It used to have some libs installed, games and utilities, but it has been a while since I took out the batteries. I don't recall where I put the cable, so I probably will have to build another one to transfer it again. But that would be another post.

[Jlouis]

(04-19-2019 03:42 PM)schuh Wrote:  Finally, yesterday I received the new polarizer.
This time I ordered the right type, a linear one.
With the linear I can find the right orientation with the adhesive side facing the display.
It's 10cm x 10cm. The display is about 6.4cm x 3.9cm.
So, it has enough material to twice tries, which was good, as it turned out to be not so simple to make straight cuts and produce exactly four right angles (one is for free, still have to do three). One of the main dificulties was to make the marks to guide the cut. Ballpoint pen isn't the proper way, but i don't have other type.

Yesterday the first try was a fail, so I decided to try again today, with daylight it's better to see
The final result was pretty fair in my oppinion. It's a little bit yellowish, but its much better now!
Now it can be used again!



Thanks for the messages and the help!

PS: The number in one of the images is the actual available memory, as I mentioned before, this calculator received a memory upgrade several years ago, and it has 128k of main memory, plus 128k of first bank attached, plus five 128k banks. It used to have some libs installed, games and utilities, but it has been a while since I took out the batteries. I don't recall where I put the cable, so I probably will have to build another one to transfer it again. But that would be another post.

Parabéns schuh! Congratulations!

Can you tell where you order the polarizer and its specifications?

I have some to fix too!

Obrigado e um abraço

[schuh]

Thanks Jlouis!
Valeu!

I bought in our "brazilian ebay":
https://produto.mercadolivre.com.br/MLB-...quantity=1

If I would to order a new one, I'd go for at least 12cm in one of the dimensions, so I would have three chances But if you have a number of displays to apply that fix, probably you'll need a bigger one. And after the first success you'll have expertise to do more with less.

The key feature is that the polarizer needs to be linear. I'm quite not sure about the angle. I can check later today and post. But I did cut at corners, 90º angles.

Best wishes and good luck!
Abraço, e boa sorte!

Saulo