15C History


I believe the first release year of the 15C was 1983.
Does anyone know is this is correct?
Any of our HP experts out there know of interesting bugs or such from the first series versus later series in 86 etc?
There's so much halfnut/fullnut history of the 41's internal development through the years; I just imagine that the Voyagers also had some kind of changes (albeit smaller ones) than the 41 did: processors, internal machine instructions, construction, etc.


Hi, Ted;

I have a few scanned images of some different Voyagers' internals, including codes for two different chipsets I found in two HP15C's.

As expected, the one showing more internal changes is the HP12C. There are four different HP12C's internals before the Chinese, 1-buttom battery version, and I have images of three of them.

I'm organizing these images and I'll let them ready to download soon. You'll be able to see the chipset codes and compare. I'm affraid I have almost nothing to say about the chips and their internal structure. All I know is based on Tony Duell's (UK) mentions. There is a "big chip", based on the HP41's "nut" chip, that contains RAM/ROM and Display Driver (R2D2 only; no C3PO) plus processing, and another smaller one that contains keyboard scanner and probably part of ROM (this is the same in all units I saw, exception made to the HP10C that I never saw inside). There is an extra small chip in the HP15C that contains extra 448 bytes RAM (64 registers) and probably ROM.

As soon as I have the images ready to download I'm posting again.

Best regards.

Luiz C. Vieira - Brazil

Edited: 15 June 2003, 10:35 a.m.


Thanks Luiz, look forward to it. Am away a lot but will keep my eye open for your posting!


My 15C has a serial number of 2234A03681.
If the sn code is correct, the unit was made in 1982.
I often purchased these calculators when first advertised.
My 16C has a S/N of 2228A08039 - also 1982


Hi, Hank;

about "clacssic" Voyagers, except the HP12C, there's a hint if you want to know what type of MBoard it has. If the battery compartment has an helicoidal spring for (+) pole and a small tab for (-) pole then it's a newer, one-board only. If it has two metal strips on each pole, then it's an earlier, older model, that has all chips, some passive components and the LCD built in a flex circuit in a small, separate assembly.

Just an additional information.

Luiz C. Vieira - Brazil

Edited: 21 June 2003, 5:20 p.m. after one or more responses were posted



Is one type to be preferred over the other?



Hi, Trent;

to be honest, from the user point of view, any of them is good. But if we consider maintenance, there are a few points to be considered:

1 - the earlier models with flex circuit allow LCD maintenance without cutting the plastic rivets;
2 - in the other hand, I'm still scared with my previous flex experience: I was not able to repair the calcualtor because the flex circuit was contaminated with battery leakage and the trails easily popped out when I tried to desolder the IC's;
3 - although the earlier models do not need their plastic rivets to be cutten in this situation, I prefer maintaining and repairing the newer, latest Voyagers mostly because their PCB is not affraid of soldering irons; I successfuly desoldered at least three times.

I know battery leakage corrodes the glue/resine that holds cooper foil over the PCB (fiberglass) as well, and cooper trails may also pop out from rigid boards, but flex circuits need specific maintenance. I'm not sure I can handle these earlier models, and I have an HP16C this type...

Best regards, Trent.

Luiz C. Vieira - Brazil

Edited: 21 June 2003, 7:27 p.m.



Thank you so much for your knowledge. I have an older 15C which I use all the time. Believe me since it is the only one I own I will be very careful about maintenence, batteries, etc. It's twenty-one years old.



Interesting. I have two 15C's with the same serial number prefix: 2234A00113 and 2234A01998. As others have mentioned, the week number is only approximate and did not change each week. They probably left it on 2234 for a while!

My earliest Voyager is a 12C: 2216A05895.

What you don't hear much of is what is the latest serial number found on each model. Collectors all seem to concentrate on the early editions. My latest 15C is a 2809A version and my latest Voyager (not including 12C) is an HP-11C 2838A69951. You know, I really don't believe that HP made 70,000 HP-11C's that week!

Which brings up another question, could the same serial number appear on two different models, or did they uniquely identify the item over all of HP's inventory?

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