Voyagers: a fifth m-board layout "found"

[Vieira, Luiz C. (Brazil)]

Hy, Voyager Fans (and users)

About a couple of weeks ago I got into contact with four HP12C's mainboards. They all belong to one of our regular contributors.

At a first look, one of them called my attention: I had never seen such layout before.

It resembles the first single-mainboard Voyagers but it has "space" for two IC's, instead of the three ones normally found in the HP11C, 15C and 16C. I have never seen the HP10C internals (but I was lucky enough seeing and playing with one HP10C in the 80's...), so I cannot say a word about it. Hey, if there is anyone brave enough to open one HP10C and take a picture, I'd gladly store it with the others.

Anyway, these three scientific Voyagers share the same layout. I also did not see an earlier HP12C (at least not yet) but I am almost sure it has the same layout; it would not make sense having more than one layout in such a factory line, I guess.

This "recently found" layout has space for two IC's and only one is used: the one that was supposed to control the LCD (named RAM/ROM/Display Driver, or R2D2 - thanks, Tony) also scans the keyboard. I thought there was one Voyager-specific IC used to scan the keyboard, but I think that this IC may have other features. The supposed KBD scanner "only" is the same one for the three Voyagers (11, 15, 16), but Tony Duel also mentions something extra about this IC; is it correct, Tony, or I am refering to you wrongly? If so, forgive-me.

And another interesting feature is the LCD's connections. Now I tell you: newre HP12C use a different LCD, EVEN those with 3 batteries. Earlier Voyagers use a different pins/connections arrangment, assymetrically distributed. These "newer" HP12C use an LCD that has connections with uniform distribution, the same number of connections in both LCD's top and bottom surfaces.

I did not remove the LCD from a newer chinese HP12C, the ones with one battery. But I saw its internals, and at components side, connetions are the same and similar cooper trails (PCB) seem to have the same functionality.

I remember reading some posts about LCD exchanging from diferent Voyagers; now I must say that in some cases, even between the newer, 3-batteries type HP12C (Indonesia, Singapore) and other earlier Voyagers, the LCD may be not compatible. Now I am curious about the single-battery Chinese HP12C: what sort of LCD does it use?

One question: I remember that the major concerns about changing LCD's in newer HP12C were related to Power Supply voltage (3.3Vcc against 4.5Vcc). I agree with the fact a 3.3Vcc LCD shoul not be used in a 4.5Vcc circuitry; LCD's timelife would be significantly reduced. Otherwise, if we consider the opposite situation, an LCD designed to work with voltages below and about 4.5Vcc could work in 3.3Vcc circuitry; dimm and viewing angle could be "adjusted" with a new polarized filter and scanning schemes.

As soon as I find a lpace to hold the scanned image I'll post it again.

I must apologise to those who kindly offered a place to hold some of my pictures and I have not yet given them a return. Thank you all; I'm just trying to find my own place, so I'll feel myself a lot more comfortable uploading stuff without disturbing host's piece..

Also, I want to apologise to those still waiting for the "HP28S explodeded view" picture. I'll surely need to scan the original article and filter image again. One of our contributor mentioned having another site with HP stuff where the original article is available.

Well, I think that's all for now. I'll collect some more data about Voyager internals and, if applicable, I'll build an article about this subject. I just want to be sure you all understand that I like Voyagers a lot for many reasons, but I'd like having more information about them.

Comments? Suggestions?

Luiz C. Vieira - Brazil

[Randy Sloyer]

I think there are at least three different LCD's in 4.5V Voyagers. I found on the very early two board units, the LCD was just the display without a plastic carrier and more difficult to align properly.

The first single board versions used the same asymmetrical pin out but was attached to a plastic carrier with two index pins. I found this LCD to be usable in the original two board unit if you remove the plastic carrier held on with double-sided tape. The solvent Undo works fine for this.

The next which I found on later 15C's (a two-chip unit) use the wider symmetrical pin out, same as the current 4.5V 12C's. I have a dead 12C 3V unit I think I will dissect tonight, I suspect it is the same display. The chip probably has a step-up converter for the LCD circuitry.

Some of the early 12C displays had silver reflectors instead of the current gold, making nice replacements for broken scientifics.

[Vieira, Luiz C. (Brazil)]

Hello, Randy;

you wrote:

I think there are at least three different LCD's in 4.5V Voyagers. I found on the very early two board units, the LCD was just the display without a plastic carrier and more difficult to align properly.

Yes, the LCD seems to be the same, but the "display set" is completely different: metal frame is "taller" in the single PCB-type, as weel as both "resistive" polymers. The plastic carrier helps keeping plymers aligned, and in the flex-PCB type it is somewhat hard to rebuild the LCD/Chipset module.

Thanks for adding this valuable info.

Luiz C. Vieira - Brazil

[Gordon Dyer]

Hi Luiz, another interesting post!

I would like to see a picture of the pcb's you refer to.

If you have no place to host them then ask Dave Hicks, he may like the pics too and post it into the guest area for you to link from your forum message.

Best wishes....

[Renato]

Don´t you agree ?

[Wayne Brown]

Luiz,

It looks like you're becoming one of our resident Voyager experts! I don't have a use at present for this information -- my only Voyager is a 16C that's still in perfect working order. But I think it's great that you (and others) are gathering this kind of information and posting it here. Someday the supply of "new old stock" and barely-used HP calculators finally are going to run out, and keeping the existing supply running will be the only way for any of us (or our children) to enjoy these wonderful machines. As more and more of them break down over the years, information like Dave is stockpiling here at the MoHPC is going to be extremely valuable for those who want to keep their precious HPs running. I'm so glad that so many people like you are donating their time and efforts to make certain this information will be available when it's needed. Future collectors and users are going to be very, very grateful for what's being done here.

[Vieira, Luiz C. (Brazil)]

Hello Wayne, folks;

I'm also glad you enjoy information like this one. I was able to turn them into concise information after many good tips from Tony Duel (mostly) and others; when we have giants' sholders to support us, the job is easier.

I am sure there is more information about Voyagers, as Randy Sloyer (thank you!) added up here. BTW, Randy, can you identify the LCD's codes? I'm still thinking if it would be possible to use newer Chinese HP12C's LCD's in the older Indonesian/Singaporean without loosing reliability. I inspected the chinese ones closer and the annunciators have a different layout, what suggests a new design. What do you think? As you mentioned the possibity of having a step-up converter to drive the LCD, did they keep the same electrical characteristics? And you added one new information: it's possible that the unit I scanned this very weekend uses the same mainboard you have in your HP15C. It seems that these (probably last upgraded) Voyagers, and not only the HP12C, used a single processor+ROM+RAM+KBDscanner+LCD_driver as we have in the newer HP12C; again, the HP15C demands an extra ROM/RAM IC. One small note: in the HP15C, if you take registers I, 0 and 1, the remaining ones that compose the "common pool" (registers+programs+advanced_functions) exactly match 64 count.

So, let me thank all of the other contributors, too; also, I'd not feel compelled to write if there are no readers.

My US$ 0.05.

Luiz C. Vieira - Brazil