Need to fix your HP48 LCD or keys?



#6

Every now and then I would read about (or see on Ebay) how someone's HP48 lost some columns/rows of pixels, or the ON key dieing out. I happened to receive such a calculator (HP48SX). This thing had ALL BUT THREE rows of pixels missing! About half of the keys didn't work! I fixed them both! Now I have another HP48SX with a fully working keybaord and all pixels returned to working order.

It seems that most of the keyboard problems, and missing pixel problems can be attributed to a combination of dust and/or being jostled around. The only electronic connection between the top part of the HP48 (LCD and keys) and the PCB are three rows of connectors. Two are for the LCD, and one for the keyboard. The PCB is held onto the top portion by 6 twist-prongs. They are also resonsible for connecting the top part of the HP48 to the PCB. If these are loose there is dust, you get columns of missing pixels and possibly dead keys.

Just a bit of dusting off and adding a little bit of extra solder to the connectors to adjust for any possible gaps that may have formed over the years and your HP48 is back to being functional!


Edited: 21 Nov 2005, 4:53 a.m.


#7

I'll write up a guide on how to repair your HP48 if there are enough interested readers. I managed to take some photos, too.


#8

Han:

That would be really nice! I also have a "spare" 48 with little problems. Maybe with your guide I would risk a repair and have one more fully functional 48.

Thank you in advance.

Valentino


#9

Here's the link:

Please read through everything first, and examine the photos I've included. The photos are of an HP48G, even though I repaird my HP48SX. However, you'll find that almost everything is the same. I just stupidly forgot to take photos of my HP48SX while I was tinkering with it. Sometimes I get too caught up in the fun of tinkering, and forget that what I'm doing might be useful enough to make note of.

HP48 Repair

There is a maintenance scheduled later this evening so if you can't download it, try later.


#10

I forgot to mention one more thing:

I believe that another cause of these dead keys it the overuse of the card slots. Every time you use a card slot, and press a ROM or RAM card into the connector, you are also pushing the PCB about. I would wager that you see more LCD and dead key problems in the X series than in the non-expandable series.

Han


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