HP 48SX dosen't turn on


hy, I hope someone can help me before I destroy my dear university pal: I haven't been using my HP 48Sx for at least 5-6 years and I've stowen it without batteries, now I tried to turn it on again ( with new batteries 3 sets) but it's dead....................................
does anyone know any solution to zthis problem?
thanks in advance


Have you tried the "paper-clip reset?" There's a small hole under one of the rubber feet on the back of the calculator. (Actually, on my 48GX there is a hole under each of the rubber feet, but the hole under the top right-hand foot has a small R next to it. That's the reset hole.) Remove the rubber foot carefully (it's not glued, just pressed in and should pry out easily with a fingernail). With the batteries installed, insert the end of a paperclip into the reset hole until you feel it reach the bottom of the hole, then press gently. If nothing happens, try pressing the ON key and try the reset again. It should cause the calculator to reboot.


Hi, Umberto;

on the way writing this message, Mr. Wayne Brown was faster... Cheers, Wayne; hope you don't mind keeping my own here... d;^)

there is a reset "shortcut" (a hardware reset) in the HP48SX.

Facing its back side, gently revove the upper-left rubber feet (in the G-series it is the upper-right) and keep it in a safe place. It is easy to remove, just swing it to the left. Try not using sharp metals or the like, your finger nail is more than enough. Now you see a small hole with a small "R" beside it. Unfolded a paper clip and insert one of its tips in the hole till it touches the board inside. Press a little bit for about 5 seconds to make sure the reset is achieved and try again. In most cases, that's all it needs.

Hope you succeed.

Luiz (Brazil)

Edited: 16 Aug 2004, 11:47 a.m.


on the way writing this message, Mr. Wayne Brown was faster... Cheers, Wayne; hope you don't mind keeping my own here... d;^)
I always enjoy seeing your messages here, Luiz. And you included something that my message didn't mention (the difference in the position of the reset hole in the S and G series). So I learned something too!

THE END IS NEAR...........................


Is there any corrosion on the battery terminals?


When your options seem to end, this only means new solutions are about to come... And never mind about their (the HP calculators) silence; they have the ability to surprise us when we least expect. Both John Limpert and Raymond's suggestions are excelent. Go for them. And there is always a chance to open the case... Later, of course.



Edited: 16 Aug 2004, 3:55 p.m.


The "R" and reset switch may be on either side on a 48SX. On a serial 3029Axxxx version D, I find them on my left, but on a 3107Axxxxx version E, I find them on my right. Perhaps the PCB design change is tied to this ROM version change?

Since the earliest reported 48S serial starts with 3107, I expect that all of them have it on the right.

It seems to me that I read somewhere of a few that have the "R" one one side, but the actual switch on the other side.

The switch is a very simple one, just a small tab from the thin metal (aluminum alloy?) shield that gets bent done to make contact with a pad on the PCB. Don't expect to feel any click, just perhaps a tiny bit of springy resistance.



Sometimes I've had luck with momentarily short circuiting the battery terminals with a jumper wire. Remove the batteries first.


See http://www.fixthatcalc.com/index.htm

He fixed my 48 with the same problem.


sorry guys, thanks for the help I've found the reset switch but still dosen't work, I'm gonna buy the last set of batteries to try for the last time..........


As your e-mail reads t-online.de, I guess it is in Deutschland... although you may not be there, of course.

Please, consider finding someone closer to you that is able to repair your HP48SX. There are many clever, skilled people in Europe that would give this baby a try. As you mentioned it's been "stuck" for many years, chances are you also have a bad [ON] key with a bad contact (I don't remember if hardware reset turns the calculator ON automaticaly... d8^( and I'm not willing to test.), so it is a waste of good stuff to get rid of it this way. I have an HP48SX working perfectly fine, except for a small oxidation spot in the display that almost hides the right-shift annunciator. Except for this, it is working fine. I'm not sure I'd replace this LCD for this reason, but if my HP48SX does not respond to keyboard, I'd do whatever needed to bring it back to life.

Well, that's just me, sorry! I just do not like knowing about a genuine HP that is not working.

Hope you succeed.


Luiz (Brazil)


I've tried all but it is still dead.
sen it to repair I think it would be too expensive, does anybody know how to open the Diabolic Thing????


Hi, I had a similar problem a few years ago. There may be a last chance for your 48sx to work correctly. Just put new batteries in the wrong sens ( inverse the polarity of the 3 batteries). Leave the batteries a few seconds and press on. Then replace the batteries in the correct position ( like you do usually). Then press on, and your sx may function correctly. Keep warning that if you leave the calculator like that too long, it will damage your calculator. So be careful. Hope it will help you.


You're very likely to destroy the zener diode,
and then your calc will suck a set of batteries in a few days.

That will be the point where the unit is really trash.

Maybe a search through www.hpcalc.org could help.



Bravo Raymond! Good advise indeed. The zener problem was bad enough that it was later eliminated from the design. NEVER put the batteries in backwards in any HP calculator. NEVER.

If the goal is to reset memory, remove the batteries and short the terminals with a wire. Yes, there will be those that say it has the possibility of static discharge problems, agreed. BUT - it is a **MUCH** smaller risk than damage from reverse polarity.

You should try pressing on the raised part of the bezel above and between the B and C keys while trying to turn it on. It is by far the most common power up problem on an SX. It is due to age and use. The keyboard bows from use and the compression pad on the keyboard connector dries and shrinks with age. Together, they conspire to disconnect the keyboard from the logic board. It can be repaired by shimming or replacing the foam pad.

The second most common cause would be damage from a liquid spill and the third a bad keyboard.


Hi, I've read your reaction about the batteries. I personnaly did this a few times and I never had any problem so I thought it was harmless for the calculator. Thanks Raymond for your quick reaction.


IF someone still insists of putting the batteries in reverse

THEN I suggest putting only two of them in reverse

thus the reverse voltage is only 1,5V (fresh alkaline) or less




Sorry guys this is too weird. I am having similar problems as UMberto. My SX showed low battery warning this morning, put new batteries in and it does not display. Old batteries back in and no display. Actually in both cases the hour-glass in the upper right comes on and it looks like the backlight or contrast comes on the normal portion of the screen. The new batteries test 1.5v (no load) and the old batteries tested 1.0v(no load) So i think that the low battery was not a lie, but apparently something else has been disturbed. Thanks for your time and suggestions. Erik


Sorry guys I can't edit my earlier post. I have already forgotten the password or I typed it in wrong to begin with.

I used a paper clip instead of my Visor reset pin (plastic)
and I held the ON button for a really long time (more from desperation than knowledge) and it came to life! WOHOOOO!!

ok where was my earlier failure? not holding the ON button long enough? Or is the reset a "short" instead of a momentary button?

Thanks guys.

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