HP41CV with unknown internal modification

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HP41CV with unknown internal modification

Postby euleken » Thu Sep 16, 2021 8:33 pm

Hello together,

A few days ago I bought a HP41CV from a local garage sale in good conditions, only the battery contacts were corroded. After opening the housing for better cleaning and repairing the contacts, I saw an unknown modification and now I'm not sure, if this is an original option. Also I don't know which function does this PCB have. Maybe this is an extra memory or other functionality module? :roll:

Google doesn't help me about PCBs numbering "5081-5558" and also I cannot find any photos or articles of a similar modification. Does someone know such a modification or the function of this two extra PCBs? I will be grateful and happy for every hint.

Thanks and regards,
euleken
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Re: HP41CV with unknown internal modification

Postby rprosperi » Thu Sep 16, 2021 10:18 pm

Photo(s) of the other side of the board may help as one may be able to see the p/n on the chips, which could help to ID them.

Most likely these are 2 ROM modules, soldered inside the case. Services to move these modules inside were offered, back in the day, by EduCALC, SOS and other specialty firms, to leave the 4 ports available for more modules. Another possibility is these are 2 X-MEMORY modules, which were also installed inside for the same reason. Since the boards have the same p/n they are clearly of the same type (as opposed to one being the X-Func/Mem and the other just X-MEM).

hth
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Re: HP41CV with unknown internal modification

Postby euleken » Fri Sep 17, 2021 6:30 pm

Hi rprosperi,

below I put a photo of the front side of the board/chips, but there's no numbering or any other signs.
I'm not very firm with handling of the HP41 yet and I don't know how I could read-out or test modules and optional functions. It would be nice to get some help here to identify this build-in hardware and for its checking.

Regards,
euleken
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Re: HP41CV with unknown internal modification

Postby rprosperi » Fri Sep 17, 2021 10:46 pm

Indeed, no information at all on that side, but thanks for trying.

To answer your original question, this definitely was NOT an original HP option, this was definitely a 3rd party modification to embed ROM or X-MEM modules inside the case.

Why not reassemble the case after cleaning the contacts appropriately and then it will be easy to check what they are.

If ROM, then CAT-2 will reveal which ones.

If X-MEM, check initially using XEQ "EMDIR" which would show a catalog of EXT-Mem and return the amount of available Ext-Mem. If that result is "NONEXISTENT" (meaning Ext-Func/Mem module is not present), insert an EXT-Func/Mem module and try again. When empty, 1 x Ext-Func/Mem & 2 x X-Mem modules should have 603 registers available.
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Re: HP41CV with unknown internal modification

Postby euleken » Sat Sep 18, 2021 7:15 pm

Thanks for this hint.
After installing a XFunction module the command XEQ EMDIR shows 600 registers of extended memory, so the built-in modules are two XMemory HP 82181. It seems curious for me, why there are two XMems installed and not one XFunction and one XMemory module... :roll:
Ok, I will not bitch. I bought this calculator very cheap and the seller (and also I) didn't know about the built-in extra memory. It was a lucky punch. ;)
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Re: HP41CV with unknown internal modification

Postby rprosperi » Sun Sep 19, 2021 2:50 am

Great, thanks for confirming these hints were helpful, and congratulations on acquiring a quite rare 41 configuration.
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Re: HP41CV with unknown internal modification

Postby floppy_stuttgart » Thu Sep 23, 2021 1:14 pm

Interesting.
Instead of creating "Double X-Memory Module" (taking 2 X-Memories and soldering it into 1 housing X-Memory), it is now possible to "Upgrade HP41CV with 2 X-Memories" (no port busy by it).
Perhaps a precise HowTo (picturing etc.) of that rare hardware setup would allow others to copy it?
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Re: HP41CV with unknown internal modification

Postby BillBee » Mon Sep 27, 2021 3:14 pm

Hey Floppy,

You need to get in touch with Jake Schwartz to get the PPC Archive usb drive. V8n1 is the issue that covered an internal module installation. It is a great investment with a wealth of information.

http://www.pahhc.org/ppccdrom.htm

Check it out. :)

-Bill
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Re: HP41CV with unknown internal modification

Postby floppy_stuttgart » Wed Oct 06, 2021 7:17 am

Thanks Bill for the answering.
My understanding after exchange offline with others:
HP41CV: bringing X-memory and X-functions parts inside an HP41CV dont free all ports.
However, your CV is very interesting.
I will not change for now my CV with your design but still focus on the use on my CX with Nov64d and double X-Memory in 1 module.
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