HP48G Problem



I have been reading and enjoying this forum for some time now. My wife thought that it was very strange of me, but she also realized that I like HP calculators. When she found the old HP48G that she bought 25 years ago, she gave it to me instead of throwing it away.

I put in fresh batteries and hit the ON button, but nothing happened. I tried the ON-C warm reset, and it came to life. "Great," I thought, "I have a new toy." But then I tried to turn it off.

At this moment, I can only turn the calculator on with ON-C or ON-A-F, and I can only turn it off by sticking a pin in the reset hole under the foot on the back (or leaving it for a while until it turns itself off). The only odd behavior I see (other than the on and off issue) is that none of the shifted ON commands work, and I cannot adjust the contrast with ON-+ or ON--.

Any ideas or suggestions to bring it back to normal? Thanks for your consideration.





Hi Jno.

I don't know if it can help, but I have a similar problem with a 48SX, which I can turn on only by pressing above the row of soft keys while pressing the ON key. Same when using the shifted ON functions. This problem is well documented in this forum.
Kind regards.


Try pressing on the bezel, below the display, while you press the ON key. The rubber support inside, tends to get lazy as it gets older.


Thanks Jean-Michel and Ron,

I appreciate your responses. Ron, your suggestion worked like a charm. I can turn the HP48G on and off now without resorting to any resets. Hooray.

Thanks again,



There is a reason for the failure and in time it may do it again:

Check out this posting for an explanation:

HP 48SX keyboard

Cheers, Geoff

Edited: 15 June 2009, 11:15 p.m.


Hi Geoff,

Thanks. The source of my problem never really went away, but Ron's message showed me how to work around it.

I'd like to tackle the source next. Would you be kind enough to describe how you took the case apart (or maybe point me to some directions online)? I came across directions for getting in from the front, but if I can avoid prying off the faceplate and drilling out rivets, I'd rather go that way. Thanks.




Hi Jno,

It seems you didn't notice that Ron and me were giving the same advice in different words...Above the row of soft keys, that's exactly on the bezel below the screen, but no matter.
Try "Openning HP-48" or something similar on Google and you may find a very well detailed site explaining with pictures how to open this calc, but if you let me give you an humble advice, do not open your calc if it turns on with the simple trick Ron and me told you. You may brake something you will regret after. That's what prevented me to try anything. I consider it's a minor problem one can live with.
Anyway, after having read the full openning procedure, you'll have your own opinion!
Kind regards.



You are absolutely right. Sorry I missed that when I read your message the first time.

And you are right, too, about opening it up. I have been doing some reading up on the different methods people have come up with for disassembling the HP48 calculators. The methods that involve cutting the case and slicing rivets are a bit troubling. I think I should practice on a few TIs first.

Thanks for your advice.



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