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Turning 41C into 41CV
03-18-2016, 04:59 PM
Post: #1
Turning 41C into 41CV
Sorry if this was discussed yet.
If I buy a 41CV with broken display would it be possible to change my 41C into 41CV just by exchanging some circuits ? which ones should I exchange?
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03-19-2016, 01:15 AM
Post: #2
RE: Turning 41C into 41CV
Better yet; If there are any more: turn it into a CL with Monty's board.

There were replacement screens and windows floating around 10 years ago. Do you want me to ask?

Anyway; buy it if there's a chance it will just be thrown away. Parts are priceless.
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03-19-2016, 01:54 AM
Post: #3
RE: Turning 41C into 41CV
LOL, I was thinking about the 'cool factor' of swapping parts around and making a TK 41C with CX innards and adding full internal XMem.

I know I've joked about maintaining the 'purity' of our machines, but some interesting hybrids would be,

well,


interesting.

And in the same vein, a 41C with 41CV functionality would be an interesting critter in it's own regard.

While we are here, do we know roughly the numbers of 41C, CV, and CX machines made, and the numbers of 'fullnuts' of each ??

2speed HP41CX,int2XMEM+ZEN, HPIL+DEVEL, HPIL+X/IO, I/R, 82143, 82163, 82162 -25,35,45,55,65,67,70,80
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03-19-2016, 10:52 AM (This post was last modified: 03-19-2016 01:15 PM by Hans Brueggemann.)
Post: #4
RE: Turning 41C into 41CV
(03-18-2016 04:59 PM)wojtek Wrote:  If I buy a 41CV with broken display would it be possible to change my 41C into 41CV just by exchanging some circuits ? which ones should I exchange?

i assume that a "broken display" means that not only the protective perspex shield, but also the display module itself is "broken".
check whether both HP-41C and HP-41CV do _not_ have the rounded-corner style display. that is, both calculators are of the "fullnut" variety, which can be identified even if the display is broken.
see here for pictures
if both are "fullnuts", then you may simply implant the motherboard of your CV, which also holds all the extra memory of the CV, into the C to turn your HP-41C into a Franken-CV.

however, if one of the calculators appears to be a "halfnut", then there is no chance to change baords.
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03-19-2016, 07:43 PM
Post: #5
RE: Turning 41C into 41CV
(03-19-2016 10:52 AM)Hans Brueggemann Wrote:  if both are "fullnuts", then you may simply implant the motherboard of your CV, which also holds all the extra memory of the CV, into the C to turn your HP-41C into a Franken-CV.

I have it, don't know yet what is wrong with it
Both are fullnuts. By "motherboard" do you mean the smaller board sitting on the main board and fasten with the 2 screws? I hope so, exchanging the main board, the one tied with melted joints, would be over my skill
Thank you
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03-19-2016, 07:55 PM
Post: #6
RE: Turning 41C into 41CV
Yes, the main '41 board is the small rectangular one that has two holes for the posts that hold the back cover in place.

My '41, if it still exists, is a very early model with all original bugs that included the ability to enter sythentic programs as-is. I also replaced its four RAMs (16 registers each in 8 pin DIPs) with the equivalent 'CV parts (actually five of those - the fifth one piggybacked on one of the four), making it a '41CV with all the early bugs. It helped to be working at HP at the time so a number of us were able to order those chips directly in-house. But the same could be done with chip swaps between '41C and '41CV main boards.

The '50g and smartphone apps blow away the '41 in capability and speed - but the '41 is still such a powerful, flexible and extensible machine that I doubt it will ever have a full successor. Viva la "Coconut" and its terrific design team!
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03-19-2016, 08:50 PM
Post: #7
RE: Turning 41C into 41CV
wojtek: You said the display is broken on the one you are considering buying, but you didn't say how it's broken. Dropping a 41 can snap the solder joints for the fingers that connect the display. If complete segments are blank, it's probably that. If the problem is a creeping black amoeba, it's a goner. The snapped joints won't be obvious but you can lift gently on each one with a sewing pin. A tiny soldering iron and some low heat solder is all you need, unless you have old eyes like me.
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03-19-2016, 09:52 PM
Post: #8
RE: Turning 41C into 41CV
For old eyes (and younger also) there is a watchmaker loupes.
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03-20-2016, 08:54 PM
Post: #9
RE: Turning 41C into 41CV
When creating a franken -41, avoid throwing any parts away unless really beyond repair (think beyond your own ability to repair, there are some very good techs in this group). Port covers, back housing, motherboards, zebra connectors, O/I block connectors...are becoming scarcer by the day and someone can probably use them for their own living dead creations
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03-21-2016, 10:59 AM
Post: #10
RE: Turning 41C into 41CV
Many thanks to all for your responses. Really helpful.
For the time being I have another probem, both machines 41C and CV are inoperative now. In my old 41C the problem is with loose 2 nuts which fasten the smaller board to the main one. The same problem is in the 41CV (and certainly some other problems in this case). The threads on plastic pegs got worn. I tried to apply an old trick with a sewing thread coiled around the pegs, which worked fine some 10 years ago in 41C, but now it not helped.
How to repair it?
BTW the LCD in the 41CV seem to be OK.
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03-21-2016, 11:03 AM
Post: #11
RE: Turning 41C into 41CV
(03-20-2016 08:54 PM)Nate Martin Wrote:  When creating a franken -41, avoid throwing any parts away unless really beyond repair (think beyond your own ability to repair, there are some very good techs in this group). Port covers, back housing, motherboards, zebra connectors, O/I block connectors...are becoming scarcer by the day and someone can probably use them for their own living dead creations

Of course, pls do not worry.
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03-21-2016, 11:06 AM
Post: #12
RE: Turning 41C into 41CV
(03-19-2016 08:50 PM)Den Belillo (Martinez Ca.) Wrote:  wojtek: You said the display is broken on the one you are considering buying, but you didn't say how it's broken.
The LCD fortunately seem to be OK, perhaps there is some other problem with the display IC, I have not checked it yet.
Thank you
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03-21-2016, 11:16 AM
Post: #13
RE: Turning 41C into 41CV
(03-19-2016 07:55 PM)Jim Horn Wrote:  .........................................................I also replaced its four RAMs (16 registers each in 8 pin DIPs) with the equivalent 'CV parts (actually five of those - the fifth one piggybacked on one of the four), making it a '41CV with all the early bugs.
Have you replaced 8 RAM IC's or the whole board with RAM and the processor?
It is made in old technology (old now) so soldering should not be a problem, the problem would be with finding today the old IC's to replace, and probably with changing the soft in ROM?
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03-21-2016, 05:48 PM
Post: #14
RE: Turning 41C into 41CV
(03-21-2016 10:59 AM)wojtek Wrote:  ..... The threads on plastic pegs got worn......

Springs come in a thousand sizes and configurations. I got extremely lucky once and found a few tiny ones of the exact right size at a flea market. They slipped over the posts of one of my 41s. I didn't even have to apply glue because they were split, not stripped.

There must be a way to order springs somewhere.
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03-21-2016, 07:16 PM
Post: #15
RE: Turning 41C into 41CV
Only the RAMs were replaced - the 41CV was produced along with the 41C for a bit if I recall, so they both used the same ROMs. The 41C had 4 RAMs, the 41CV had 5, each of which stored as much as one of the 41C's RAMs did. Thus the "V" for a 5x storage compared to the 41C.

Exchanging the processor circuit boards would be the most direct way to go rather than exchanging the ICs. But if the CV processor board isn't working but the C board is, the CV RAMs may be usable as described. They may also be why the CV board doesn't work, in which case the exchange would not help.

There is lots of expertise among those in this Forum. Glad to help in any way I can!
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03-21-2016, 07:20 PM
Post: #16
RE: Turning 41C into 41CV
For repairing the damaged posts in the '41, there has been clear information worth searching for about replacing them with brass ones. That allows metal screws to hold the '41 together and simple spacers between the processor board and the back cover to hold the processor board in place.

If the self-tapping screws that hold the back cover have left stripped holes, HP kept longer ones in stock for repair as they would tap into the unused depths of the holes in the posts. A check of the existing screws and hole depths should tell us what we could find to do just that as well.

Your '41s will live again - it may just take some time to deal with each issue. Best to you!
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