48GX; can this be fixed?



#2

Hello,
I'm looking into buying a graphics calculator.
Having RPN hardwired into my brain from 24 years of using a 15C, it has to be a HP.
While searching for a 48G I found this
48GX on ebay

quote

The cosmetic condition is very good, but unfortunately, the calculator does not work properly anymore. Some keys activate two functions at the same time, e.g. when you press '3', the divide operation is activated, too.

/quote

What do you think, can this be repaired? I hope this one will be not to expensive.

Another question: How does a 48G/G+/GX or 48S/SX compare to a TI-83 in terms of speed. Most of my pupils use a TI and I don't want them running circles around me and my HP when doing, say, a numerical integration.

Do you have any recommendations like Rom versions/serial #s to avoid? I'm mostly looking for a 48G. If the RAM turns out to be to small I'll try to turn it into a G+ (if I can find a chip).
A GX in good condition is expensive, a S/SX maybe to slow.

Thanks
Rainer


#3

It is possible that your problem can be fixed. But I'd say it's about 50/50. The other possibility is that your keyboard circuit is simply shot. If it is a short of two address lines (which would cause two keys to register even though only one is pressed), then it may be possible to locate the short and fix it. One possible example is if some tiny piece of metal somehow connects two address lines (say it gets stuck where the card connector attaches to the PCB).

If on the other hand your keyboard circuitry is shot, then your only recourse is to replace the entire keyboard using one from another HP48.

See

http://www.math.uiuc.edu/~handuong/hp48/repair

and

http://www.hpcalc.org/hp48/docs/misc/hp48sch.zip

As always, you can easily further damage the calculator by trying to fix it on your own. Opening the HP48 itself in a manner that does not structurally or cosmetically damage the unit too much is oftentimes an extremely hair-raising experience for first-timers (and I cannot even begin to count the emails I've received from people who screwed up the HP48 in attempt to fix something).

But if you are good at tinkering with electronics and are used to taking things apart and being able to put them back together, then it may be worth your while (esp. if you can win with a relatively low bid).


#4

One more thing -- make sure you ask as many questions about the condition of the calc as possible. It would be in your best interest to ask if the unit has already been opened up before, etc. The seller seems honest, and the feedback is good, so you may be in the clear. But it never hurts to be safe :-D

#5

I would look for a 48G or 48G+ in mint or new in the box (NIB) condition first before considering the problematic GX. They can be bought for under $100 on ebay.

Now in terms of processing speed, I think you may want to consider the new HP 50g that uses the ARM processor. The Saturn processor in the 48 series will not keep up with the modern TI calculators.

Of course a big consideration is the quality and feel of the buttons. The 48G series is without a doubt the best compared with your 15C. However, the 50g is reported to be very satisfactory and will be far better than the TI buttons. A word of caution, don't buy the HP 49 series. The buttons are problematic.

Good luck!


#6

Quote:
I would look for a 48G or 48G+ in mint or new in the box (NIB) condition first before considering the problematic GX. They can be bought for under $100 on ebay.

Thank you all for your answers. I have been looking into a 50G but around here it's $200 minimum, a bit steep for me. I think I'm trying to get a good 48G/G+/GX. The Gs are cheaper but the RAM may be to small, G+s seem to be rare.

Why is the 48GX problematic?


#7

I was refering to the 48GX that you were considering with the keyboard problems. The 48GX is great calculator.

#8

Any newer series Hp calculators after your Hp15c are not meant to be repaired ie there are no screws, these calculators are ultrasonically welded together. Yes, they can be repaired, but this shouldn't be relied upon as a way to get a working RPL graphics calculator.

I too, second the suggestion to buy a new or in excellent shape Hp48G. But I also suggest you buy the more modern and much faster Hp50G if you want something compariable to the Ti series for a graphing calculator. I don't use the graphing feature all that much on any of the graphic calculators I do own. However, if and when I do, I don't bother to reach for an Hp48G for the simple fact that it IS THE SLOWEST graphics calculator around! (it is however the one I use most). Why is this? Well the Hp48G is a great quality calculating device. It still has that Hp feel and quality that I want (And that large enter key where ITS supposed to be!!).

But most of the old Hp quality has been put back into the new Hp 50G (as far as keyboard feel, its to early to tell whether the quality is truly there). But it is fast and it is loaded with lots more features than even the older Hp48G series with the addition of CAS (not a big deal to me as I use either as a number cruncher, not a math package).

So, my suggestion is to buy both! However, if you can only buy one (and Your MAIN goal was to acquire a graphics calculator!), buy the Hp50G. But download or acquire an Hp48G user's manual as that is 10X better than the Hp50G manual and 98% of it applies to the newer calculator.


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