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A very weird HP48G
09-26-2021, 01:21 PM
Post: #1
A very weird HP48G
Hello,
I recently moved to a new house and I found an HP48 that is puzzling me. It had been misplaced and I have no idea where it came from, but it's in pristine condition, with no sign of ever having been open or tampered with. It still had a $10 consignment shop price tag, with a like-new pouch but no other accessories. There were dead, but still clean, batteries inside.

Anyway, I put in fresh batteries and turned it on. It greeted me with the usual "Try to recover memory?", I answered no, and it gave me a "Invalid card data" message. Weird.
Then I checked the free memory, and it gave me 127856 bytes free.

It's definitely a 48G, it's not just a wrong faceplate (there's no card door on the back). It's made in Indonesia, and has the printed key labels.

Apart from this, it behaves exactly like a GX, the extra memory can be freely used, and I get no unexpected behavior... except that when I turn it on, I always get the "invalid card data" which I can dismiss and keep working.

So, what's this thing? Has it been (very skillfully I'd say, since there are no marks) opened and upgraded internally? Is there an easy way to check what's "attached" to the external ports, that is giving that "Invalid card data" error?

Is there some detailed information online on modifications like this, since I assume it didn't leave the factory like this by mistake?

Thanks,
Cristian
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09-26-2021, 01:49 PM
Post: #2
RE: A very weird HP48G
Hi Christian,

try PINIT

Check out
https://www.hpcalc.org/hp48/docs/faq/48faq-6.html
chapter 6.23 Why do I get an "Invalid card data" error when I merge a RAM card?

best regards
Michael
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09-26-2021, 04:03 PM (This post was last modified: 09-26-2021 04:05 PM by Kiwi.)
Post: #3
RE: A very weird HP48G
I once had a similar HP48G. It was upgraded by a German company called Cynox. They upgraded the unit to 512K RAM (with 128K as internal user memory, 128K as Port 1 and 128K as port 2 & 3). It was very professionally done, you couldn't see any trace of opening the unit.

As Michael mentioned, please first use the PINIT command, then you will probably see the additional port(s).
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09-26-2021, 10:51 PM
Post: #4
RE: A very weird HP48G
Thank you. PINIT solved the port error message, now I can see ports 0,1,2 and 3. Now I'll have to find out again how to check their size and how to transfer files and install extensions... It's been like 20 years since I really used a 48 as my main calculator...

On the faq linked above, there are two links to pages that should describe expansions like this, but both links are broken.

Does anyone have an idea how much this 48 might be worth? Not that I plan to sell it, it's too good a toy... Smile

Cristian
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09-27-2021, 08:34 AM
Post: #5
RE: A very weird HP48G
(09-26-2021 10:51 PM)Cristian Arezzini Wrote:  On the faq linked above, there are two links to pages that should describe expansions like this, but both links are broken.
Wayback Machine to the rescue, I think:
HP 48 Calculator Unofficial Upgrade Page ("Whopping 4MegaByte for HP48G?" on geocities)
Info about upgrading to 768k. (Stefano Garavaglia)
Upgrading by yourself the RAM of your HP48G to 256K (Stefano Garavaglia)

(See also Stefano's home page, here and also here.)
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09-27-2021, 01:39 PM
Post: #6
RE: A very weird HP48G
(09-26-2021 10:51 PM)Cristian Arezzini Wrote:  Thank you. PINIT solved the port error message, now I can see ports 0,1,2 and 3. Now I'll have to find out again how to check their size and how to transfer files and install extensions... It's been like 20 years since I really used a 48 as my main calculator...

On the faq linked above, there are two links to pages that should describe expansions like this, but both links are broken.

Does anyone have an idea how much this 48 might be worth? Not that I plan to sell it, it's too good a toy... Smile

Cristian

I paid $40 each for the 2 48G s that I own, but that was around/over a dozen years ago.
One came with the case and a manual.

10B, 10BII, 12C, 14B, 15C, 16C, 17B, 18C, 19BII, 20b, 22, 29C, 35, 41CV, 48G, 97
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09-27-2021, 01:50 PM
Post: #7
RE: A very weird HP48G
(09-27-2021 08:34 AM)EdS2 Wrote:  Wayback Machine to the rescue, I think:
HP 48 Calculator Unofficial Upgrade Page ("Whopping 4MegaByte for HP48G?" on geocities)
Info about upgrading to 768k. (Stefano Garavaglia)
Upgrading by yourself the RAM of your HP48G to 256K (Stefano Garavaglia)


Thank you!

Ren Wrote:I paid $40 each for the 2 48G s that I own, but that was around/over a dozen years ago.
One came with the case and a manual.

Yes, that's more or less right for a vanilla 48G bought a few years ago (now they tend to be more expensive). But I was wondering specifically about one modified like mine, in pristine condition...

Cristian
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09-27-2021, 02:14 PM
Post: #8
RE: A very weird HP48G
Unless its a 48G+ the person who upgraded it was really good. Usually they are tough to get apart without any signs. Its a long faceplate on that puppy to remove in order to drill the rivets and the brute method usually leaves a mark or two.

Don't do this - but if the rivets were drilled and not glued prior to reassembly the calc should be easy to pop apart. Don't do it.

-Bill
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09-27-2021, 06:58 PM
Post: #9
RE: A very weird HP48G
With some practice, they can be popped opened and closed without any external evidence. It’s only when you open them again you will see epoxy or whatever method that was used to close them back up.

I’ve upgraded hundreds of G’s to 128K, it’s only the ram chip that changes and you don’t need to remove the logic board if you hand solder. If you use hot air, I’d recommend removing the logic board.

Perhaps the only external tell is the positive battery clip. If the clip isn’t bent into the correct profile before closing it up, the clip will sometimes be too high and not lock the slot in the clip onto the plastic tab of the case back.
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