HP-48GX display indicators


All 4 display indicators (ALPHA, BAT, BUSY & CONNECT) of my HP-48GX are always on, regardless of mode and/or battery status. Does anybody know what could cause this? Is this perhaps an indicator for a faulty display or contact problems, or just a flag setting?

Axel Poqué


I suspect it to be a display contact problem.

Somewhere here on this site there are/were articles/postings related to this topic.

Have you tried applying (carefully) some torsion on the calculator case?

What about installed software, and/or new batteries?



The calculator has had this problem for quite some time now (several years - I just didn't know who to ask before), so it's not a battery issue. I have a 1 Mb RAM card installed, but the indicators stay on when I remove it. There's only one additional program installed at the moment, because I lost the contents of the RAM card recently when its battery died, and I didn't bother to reinstall until now.

Flexing the case doesn't change anything.

When I change the contrast setting, the indicators do not change - they have always maximum contrast (is this normal?).



On the newer 49 and 39 series, this indicates a problem with the battery circuit (high drain due to diode problem, maybe in past you inserted a set of batteries backwards?). That said, a set of batteries will only last for a couple of weeks to a couple of months vs normal useage on a set of batteries should be 3+ months under even heavy use.

I have a 39G that was replaced with the same problem, but it was still under warrenty. But it didn't seem to use up batteries any more than my daughters other 39G either.


Well, I know that I once inserted at least one battery backwards; but I discovered it immediately and put them in the right way. I can't remember if my problem started then, though. (I hope I didn't damage it.)

Up until about 3 years ago I used my HP-48GX almost daily for about 6-8 hours, a set of batteries used to last about 6 weeks then. Now I use it much less and I really can't tell how long a set of batteries lasts.

I'll probably back everything up and try a complete reset (as someone suggested) and see what happens.



Putting one out of the three cells in backwards will result in the battery voltage being at about 1.4 volts with the correct polarity, same as a low battery condition, and should not cause any harm to the hardware. The calculator would probably just not run. It might cause loss or corruption of the memory though.


I have a 49G that had the same problem (bought used).
Last week I decided to swap the lcd screen (with a "donor" 39G) and this took care of the problem, my 39G now displays the indicators and my 49G works flawlessly.
Now you know what to do... find an old 38G or 39G and replace that screen.
Hope this helps.





I remember you posting about this----but was it here, or at comp.sys.hp48?

Some of you guys here in this forum are damn good at taking apart machines that were not designed to be serviced, and you manage to perform the electonic equivalent of brain or eye surgery.

I am impressed, amazed, and perhaps even a bit intimdated. I have not had so much luck myself so far with calculator surgery :-(




Hi, Bill;

I see and read your posts here and let me tell you something: I think no one likes to post about losses, both because it's not a good thing to read about and may also cause lack of confidence in others.

I was not completely successful in all of my surgeries. I still have a deceased HP42S with 32K RAM, I could not repair some calculators sent to me sometime ago, but I feel I can do better.

We have a big advantage against doctors: we can kill our patients and resuscitate them anytime we want, even after days, months passed after they're "put to deep sleep".

I am a lot careful, I do not feel as having the rights to go beyond what I know I can, mostly when I have someone else's equipment in hands. A couple of months ago I was given an HP41CV, halfnut, with an intriguing behavior: only 64 registers available. What did I do? I disassembled it all, scanned its "guts" and allowed people to "see" the inside of a halfnut in a way many have never seen before. After that, I put all stuff back, soldered all necessary junctions and it woke up the same way it was before: only 63 registers. Now I use it as my first "fake" HP41C halfnut. Yes, I rebuilt it in a fulnut HP41C's original case.

I only give up when I "see" no way out and there is no one else to show me another alternative. Before getting acquainted with the MoHPC "environment" I had three HP41 disassembled and out-of-order. I was able to bring two of them back to life. The third one I'm using as an "organ donator". As I have seen in some movies: "Someone must do this job", right?

Best regards. And don't give up... Use a faulty experience to compose a new, successful one.

Luiz (Brazil)


Hi Luiz,

Tnx 4 the encouragement. BTW, my 41cv fullnut--the one that I have not fixed yet----before it wierded oit on me, when I went to empty program space, it would say "Reg 63" or "end Reg 63" or something. Does this mean I only had 63 registers, too?




Hi, Bill;

based on what you say, chances are you have only a faulty RAM IC, maybe more. When you force a [MEMORY LOST] condition and execute SIZE 000, you get [00 .REG. 63] in PRGM mode, right? After doing that try one of these:

[RCL] 64
128 [RCL][SHIFT][.] X (i.e. RCL IND X)
192 [RCL][SHIFT][.] X

If any of these does not generate [NONEXISTENT] then you have only one faulty RAM chip. In this case, and of course, being it a be a fulnut, chances are you can repair it with a donated RAM from another CV. Fulnuts have all RAM chips as separate, discrete package. Halfnuts have an hybrid chip with all ROM, RAM and display driver (R2D2) in one single resine package that cannot be serviced.

Would you please check it out and let us know?

Best regards.

Luiz (Brazil)

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