Voyager series (HP-1xC) internals question


Does anyone have an HP-15C that uses the 1LE2 ROM/RAM/display driver (the largest of the three chips)? This would be used in either the two-board or single-board HP-15C designs. Both of the ones I have inspected recently have the newer 1LH1 ROM/RAM/display. So if anyone has a 15C with the 1LE2, I'd appreciate it if you could let me know the part numbers of all three chips.

In fact, I'd be interested in hearing about any Voyager chips other than these:

CPU: 1LF5-0301,

RAM/ROM/Display: 1LE2-0308 (12C),
1LE2-0322 (16C),
1LH1-0305 (11C),
1LH1-0306 (15C)

RAM/ROM: 1LH1-0302 (15C)

Single-chip: 1LQ9-0322 (12C)




I found these on a old model HP-15C picture here in the museum:

Display controller+RAM+ROM: 1LE2-0321
RAM+ROM:1LH1-0302 (or -0307? the image is blurred)

It would be interesting to track the serial numbers and PCB format (keyboard + flex or only one PCB).

Best regards,



Hi Nelson, guys;

I'm adding a link to an old post of mine that may add some extra info. After Nelson's informations about Voyagers, I'd like you to correct my wrong information about the R2D2 (RAM/ROM Display Driver) that I used to take as the CPU as well, and the so called "keyboard scanner", the nut CPU itself. As you can see in the old post, the nut CPU has two different series, but they are compatible with the both R2D2 as well.

The "hybrid" HP15C is till "alive" and doing as fine as any of the other Voyagers I have.


Luiz (Brazil)

(Eric, I think I still have some interesting scanned images; I'm sending them to you later, O.K.?)


FWIW, here's the only 2 chip'er I have (2833B):


Is available for rom sucking if desired. Is in a state of disassembly as the PCB is out of the case.


Is available for rom sucking if desired.

Thanks! I would like to do that; please email me to arrange the details.

Perhaps even more interesting than romsucking will be tracing the connections between the 1LQ9 and the 1LH1. I wasn't sure whether the 1LQ9 had ever been used in a 15C, as I'd only seen it in a 12C. I wasn't able to dump that 12C because I didn't know what pins had the bus, and a quick (5-minute) exploration with the LogicDart didn't find anything familiar.

It's possible, in fact, that the 1LQ9 variants used in everything but the 15C might have the external bus disabled.


I've put together a web page detailing the information I have on the combinations of integrated circuits used in Voyager series calculators:

Contributions to fill in the blanks are appreciated, especially with serial numbers and scans or high-resolution digital photos.


There was one HP-12C that used 3 button battery cells before the 1 cell 3V coin one, and it used the 1RR2-0001 single chip, standard 80-pin smd packaging (16+24+16+24 pins) produced by HP, made in Malaysia.

The China made 12C used the 1-cell coin battery and used the 2AF1-0001 chip, same 80-pin standard packaging and produced by Agilent.

I have pictures of them that I get from Luiz Vieira, I'll send them to you.

Don't forget to put the HP-15C 1st version combination of 1LE2-0321 + 1LH1-0302 + 1LF5-0301 on your table!

Best regards,



Added more photos of Voyager internals, including the top side of a board, the keys in the top case, etc.:

And a photo of an HP-21 probed for dumping:


Has anyone ever tried, with the front case off and the calculator on, pressing the lower of the two discs under the Enter key? I wonder what actions are called forth in the various Voyager models (if any) . . .


All HP handheld calculators from the HP-35 through
the Voyagers have an unused switch contact under the
"other" half of the ENTER key, with the possible
exceptions of the 10 and 19C. I'm not sure whether the
Topcat family (desktop printing, 91, 92, 95C, and 97) or any of the Saturn based calculators also have it.

On the HP-45 the extra switch was famous as the way to
enter stopwatch mode. This was done by pressing RCL
followed by the right half of ENTER. The trick was that
the molded ENTER key did not press the right half. You
could either press CHS, 7, and 8 (or certain other combinations) simultanously to get the right half as a "phantom key" due to the way the key matrix is wired and the scan order, or you could add a shim under the key.

On most if not all of these calculators, the extra key does something. However, what happens is that the calculator executes a "KEYS->ROM" instruction to do a computed branch based on the key code. The addresses between those of valid keycodes were usually used for short code snippets, so unless the programmer made specific plans for the extra key, it's going to most likely do something entirely useless.

After the first generation (Classics), they added an instruction that reads the keycode into the C register. Some calculators use that instead of "KEYS->ROM", so they may not jump into the arbitrary code location, but they most likely still do not do anything particularly useful.

However, I have not made a study of exactly what they do, so it's possible that there could be something interesting in one or more of the other models. Probably nothing nearly as exciting as the HP-45 stopwatch, which was written because the hardware design provided 512 words more ROM than the calculator needed.


Eric; Not an argument - just a question. I have a 41 open right now (ser # 2029A00211). I don't have the keyboard off but the board is opaque and i think that it only has one disc under the enter key. Is this one an anomaly or am i cross-eyed?


Hi, folks;

about the HP41 ENTER key: there's only one metal dome under it in both full- and halfnut models, as shown in picture below.

About Voyagers, the pictures below also show a "button" ENTER dome without the related metal contacts found in the motherboard of all others. (this is a newer HP12C made in Malaysia)

As you can see, the horizontally aligned assemblies have groups of 5 domes, each one connected to its neighbor, so there's no need for such PCB contact. Anyway, the centered contact with a metalized hole is also absent, so the dome is a "dummy" dome. I guess if the earlier models had it doing something...

Hope these images help a bit.


Luiz (Brazil)

Edited: 5 Feb 2004, 10:53 p.m.


Sorry, I was mistaken about the 41C. And I was unaware that although the Voyagers have a snap-disc in the extra position, they don't have an electrical contact, as Luiz points out.



Your own photos of earlier units are what prompted my question.

Luiz' pictures are of a more recently manufactured 12C. Apparently its redundant contacts have been removed from the PCB mask, but your pictures of earlier units seem to show the extra connections were indeed implemented, once upon a time.

- Paul B.

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