HP48 display problem


I've just been given a HP48GX with a problem. Now I know absolutely nothing about these things. The problem is that some pixels don't display properly, either always on or always off. The curious thing is that it appears to be basically in two lines, but diagonal lines across the display. One set is near the bottom, and the other set just above the "4:" near the top. Seems to be a bit of a problem at the very top line of pixels too. If any one has any suggestions about this problem (apart from "throw it in the bin"), then please let me know. Thanks - John


I had a 48SX who died due to static electricity, which switched some pixels permanent "on" and gave random errors. In your case could it be a connection problem: try to "warp" it a little bit (not to much). If the dots switch on and off it's a connection problem in the rubber between the LCD and the printboard. Though an connection problem will cause pixels (and mostly a compleet row) not to function in stead of functioning when not wanted.

Dit you perform the selftest?



Here is something else to try. This worked for an old monochrome notebook PC that I had and has also worked on at least one HP48GX (not mine). Remove the batteries and let the machine set for a day or so. Press the on key a few times. Then put fresh batteries in, not the ones you took out. This MAY fix the display problem. Seems some of these displays can get a "memory" from a charge buildup or something. You might also try shorting the contacts in the battery compartment (without batteries of course).

I have not heard of a diagonal line problem, but I know this fix has worked on HP48 calcs with verticle or horizontal lines.


Hi Charles,

Thanks for the suggestion, I'll give it a shot. Does anyone know how to dissassemble a 48 ?? Thanks - John


Do I know how to open a 48?

Well, I've seen it described, but I wouldn't wish it on my worst enemy's 48.

I found it by doing searches on the web for something like "hp48 disassemble"



I've taken both of my -48G's apart, added memory, and put 'em back together, and they work fine.

HPCALC.ORG has a number of files that can be downloaded which describe memory upgrades for HP-48G's. Opening the calculator is a crucial 1st step. Search on "diassemble 48g" or "open 48G".

One thing, though: you DON'T need to take off the foil keyboard overlay on the front of the calculator. Some of the early directions suggested this step to release some melted plastic rivets that hold the case halves together -- it turns out it's unnecessary.

It's been so long since I've done it, I don't know which are the best directions, and I don't have time to wade through 'em all right now. (I took a cursory look, but I can't keep at it . . .)

My memory tells me I had to cut away some of the plastic posts from inside the battery compartment, release the front case at four or six points around its edge through tiny slots in the edge of the keyboard, and (I think) gently yank the thing apart to break the internal plastic rivets behind the keyboard. (This last part I'm a bit fuzzy about, because that's what I've done with my Pioneers, too.) In any case, DON'T take the foil off the front -- it'll never go back on as nice as it was!

Good luck!



After claiming I had no time, I continued, and found Adrian Drury's article "How2Open" at www.hpcalc.org . (Just search "How2Open" as one word on their site, and it's the only "hit".) It's a well-illustrated download that lets you do a cosmetically clean job of opening an HP-48. Like I say, I've done two this way, and the method described works fine.

I remember struggling a bit with the screwdrivers in the little slots trying to get the edges freed -- it ends up easier than I thought going in -- just take your time and be gentle. (In fact, the best tool for the job that I found was a metal stay from an old brassiere -- a flat piece of metal about 2mm x 6mm -- it went further "in" than did a screwdriver bit, which widens too quickly.)

Again, good luck!

(And don't worry too much -- 48G's are going pretty cheap these days . . . )


Hi Menno,

I already tried "warping" it a bit, but to no effect. How do I perform a self test ?. I have no manual, and I know nothign about these things. Thanks - John


Get a Manual, without it you will never learn how to use the 48 properly. And it will answer a lot of questions !!!

Download the 48sx manual if you are low on cash




the self test is
1 turn the calc. on.
2 press and hold 'ON'
3 Press and release the 'E' key
4 Release 'ON'

It will repeat continuously until you do a system halt

1 press and hold 'ON'
2 Press and release the 'C' key
3 Release 'ON'

If you get fail of course it needs service.

There is also a keyboard test.

1 turn on the calculator
2 press and hold 'ON'
3 Press and release the 'D' key
4 Release 'ON'
5 Press and release the 'E' key. KBD1 will appear in the upper left corner of the display
6 starting at the upper left corner and moving left to right, press each of the 49 keys on the keyboard.
Make sure it's in that order and when you reach the last key i.e.'+' the display should change to KBD1 OK.
By the way, there is a high pitch noise when eah key is pressed.

hope this helps.

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