Thinking about an HP-41CL

[smp]

Hello all,

I got my first HP-41C way back in 1980, or thereabouts, if my memory serves me correctly. As is the case for some, it fell into disuse in time, mostly because I was a young married, and we did not have a lot of $$ to put into a calculator hobby, and I made the whopping mistake of selling it to a collector. Now, I am a bit of a collector, and I deeply regret that decision. SIGH.

Over time, I've noticed that HP-41s are still available (at somewhat outrageous prices on eBay) and there is also the Systemyde HP-41CL upgrade. I am wondering about possibly obtaining an appropriate (I've already been scanning the CL manual) HP-41C or CV, and ordering the CL upgrade.

I know that some folks on this forum have done this. Even though I am late to this party, does anyone have any comments, hints, or advice to offer about this? I already have a couple of HP-71Bs, and I have an HP Prime. Am I fooling myself that a turbo-charged HP-41 will be anything more than a real cool toy?

Thanks in advance for any thoughts you may want to share.

smp

[cruff]

(07-23-2016 08:54 PM)smp Wrote:  I know that some folks on this forum have done this. Even though I am late to this party, does anyone have any comments, hints, or advice to offer about this?

The conversion itself is straight forward. You may find, though, that you need to perform a repair for broken screw posts. When I did mine, I had to replace the lower posts only. I used a pair of 2-56 threaded spacers that I had to reduce their outer diameter (chuck into a drill and grind) and then cut to length to fit through the 41CL board mounting holes. Then use fresh epoxy, align the replacements by screwing the halves of the calculator back together, along with a bit of weight to ensure the posts set up in the right place. Wait a whole day before touching it to ensure the epoxy has set fully.

[rprosperi]

(07-23-2016 08:54 PM)smp Wrote:  I am wondering about possibly obtaining an appropriate (I've already been scanning the CL manual) HP-41C or CV, and ordering the CL upgrade...

Am I fooling myself that a turbo-charged HP-41 will be anything more than a real cool toy?

If you like using a 41C even a little, you will really love using the 41CL. It has the max memory possible, and essentially lets you load ALL the software ever written for the 41 back in the day, plus all of Angel Martin's remarkable new ROMs released in the past few years. This includes all the capabilities of the esoteric and rare modules like the CCD ROM, MLDL, HEPAX, Zenrom, and on and on.

Straightforward to learn, the CL commands are logical and intuitive. Once you get used to using a 41CL, going back to a 'normal' 41C seems extremely limited.

Regarding speed: The 41CL is up to 50x faster than a stock 41C, (which is still slower than a Prime...) but the speedup was well thought out and implemented so things that need the original speed (HP-IL, clock functions, etc.) are handled automatically.

One thing you may not notice initially: the 41CL ROM provides all the ROM of a 41CX, so a cheaper 41C/41CV can be upgraded via the CL board, but it also requires an original TIME module for the clock/alarm functions, as that module provides the required crystal chip for the clock (likely not the most accurate description, but you get the point).

And do get the Serial Port option as uploads and downloads are trivially simple and quick.

Recommended!! You won't be sorry... and if you are, I'll buy your 41CL board.

[Ángel Martin]

(07-23-2016 08:54 PM)smp Wrote:  I know that some folks on this forum have done this. Even though I am late to this party, does anyone have any comments, hints, or advice to offer about this? I already have a couple of HP-71Bs, and I have an HP Prime. Am I fooling myself that a turbo-charged HP-41 will be anything more than a real cool toy?

I'll be hard to over-state the features and excellence of the 41-CL, it is by far the best investment you can make on the series and it turns the machine into a powerhouse. Absolutely recommended, just make sure you find a suitable donor to avoid getting into hardware repairs (unless of course you also enjoy the DIY involved).

Cheers,
'AM

[smp]

Cruff, Bob and Angel, thanks very much for your responses.

I am psyched. I just scored a nearly mint HP-41C on eBay, through a Seller that I've dealt with before and who I trust:

http://www.ebay.com/itm/142062053596?_tr...EBIDX%3AIT

I know that I probably just paid way too much for it, but I fell in love with its pristine condition. And there was the trust factor I have with dealing with someone that has done well by me in the past.

Now, if I could only score a good rechargeable battery pack for it. Does anyone have any good pointers for that?

I also found this battery shield on eBay (I have not yet purchased):

http://www.ebay.com/itm/162095517736?_tr...EBIDX%3AIT

Has anyone used one of these (I've never seen one of these before)? If so, do you recommend using one, or is it a waste of time?

[Dave Frederickson]

(07-24-2016 05:05 PM)smp Wrote:  Cruff, Bob and Angel, thanks very much for your responses.

I am psyched. I just scored a nearly mint HP-41C on eBay, through a Seller that I've dealt with before and who I trust:

http://www.ebay.com/itm/142062053596?_tr...EBIDX%3AIT

I know that I probably just paid way too much for it, but I fell in love with its pristine condition. And there was the trust factor I have with dealing with someone that has done well by me in the past.

Now, if I could only score a good rechargeable battery pack for it. Does anyone have any good pointers for that?

I also found this battery shield on eBay (I have not yet purchased):

http://www.ebay.com/itm/162095517736?_tr...EBIDX%3AIT

Has anyone used one of these (I've never seen one of these before)? If so, do you recommend using one, or is it a waste of time?

I, too, have purchased calculators from jones.sebago.lake aka Adam Jones or aj04062 as he's known here, including a 42S and fully-working 97. See Bob's HHC 2014 presentation, Adam is a recommended seller.

I also have a battery shield, but about the only thing I can figure out it's good for is holding the batteries in place in the holder when it's removed from the 41. It will fit inside the calculator but will not fit on a rechargeable pack. As an alternative to a rechargeable pack, consider NiMH N-cells which can be recharged in modern smart chargers.

Dave

[rprosperi]

(07-24-2016 05:05 PM)smp Wrote:  Now, if I could only score a good rechargeable battery pack for it. Does anyone have any good pointers for that?

I also found this battery shield on eBay (I have not yet purchased):

http://www.ebay.com/itm/162095517736?_tr...EBIDX%3AIT

Has anyone used one of these (I've never seen one of these before)? If so, do you recommend using one, or is it a waste of time?

I echo Dave's comments about the 41C seller - Adam is as reliable and fair as any seller I've ever bought from.

See here for a reliable rechargeable battery. This seller, Scott, is another reliable long-standing and trusted seller, who offers a lifetime warranty where he will replace the cells if they ever fail, plus the price is good as well. Recommended. I bought one here and have had no problems.

The purpose for the shield is stated to be to prevent leaking batteries from damaging the sensitive contacts in the 41C. While an admirable goal in general, it's probably unlikely that you would buy a vintage 41C, then upgrade it to a 41CL, and then forget about it in a drawer long enough for the batteries to fail, leak and cause damage. I should say here that I've never used one and I'm not criticizing it, I'm just questioning if it really applies in this case.

[hth]

(07-24-2016 05:05 PM)smp Wrote:  Now, if I could only score a good rechargeable battery pack for it. Does anyone have any good pointers for that?

I also found this battery shield on eBay (I have not yet purchased):

http://www.ebay.com/itm/162095517736?_tr...EBIDX%3AIT

Has anyone used one of these (I've never seen one of these before)? If so, do you recommend using one, or is it a waste of time?

Get some rechargeable N cells and a suitable charger, I have been using that for years.

I suppose the shield is to protect the contacts from leaking batteries. Having used alkalines, NiCd N cells, NiMH N cells as well as HP's rechargeable pack over the years without any leaks, I do not think you need that. Just remember to take out the batteries when you do not use your calculator for a longer time.

I just entered the 41CL crowd by updating my early 41CV just a few weeks ago. I upgraded my old 41CV (bought in '81, I did not sell it, I kept it!). Now it is making my Halfnut CXs pale a bit.
It is so solid (after some internal repairs) and snappy. That dog slow ED program (built in CX text editor) just flies!

[Sylvain Cote]

(07-24-2016 08:22 PM)hth Wrote:  Get some rechargeable N cells and a suitable charger, I have been using that for years.

I agree,

I personally use full size rechargeable 500mAh N size batteries (GP 50NH 1.2v 500mAh) with a charger from La Crosse Technology (BC700 or BC1000).
I also have several rebuild HP-82120A, but my experience is that full size N hold more charge than the battery pack.

Sylvain

PS: be aware that there are 190mAh rechargeable N on the market, only take the ones with 500mAh rating.

Edit: after a research on the web I found that the GP 50NH is no longer produced but I have found a replacement in XCell X500NH.
Unfortunately, it seems that it is only available in Europe, all resellers that I found do not ship to USA or Canada.

[Dave Frederickson]

(07-24-2016 11:28 PM)Sylvain Cote Wrote:  

(07-24-2016 08:22 PM)hth Wrote:  Get some rechargeable N cells and a suitable charger, I have been using that for years.

I agree,

I personally use full size rechargeable 500mAh N size batteries (GP 50NH 1.2v 500mAh) with a charger from La Crosse Technology (BC700 or BC1000).
I also have several rebuild HP-82120A, but my experience is that full size N hold more charge than the battery pack.

Sylvain

PS: be aware that there are 190mAh rechargeable N on the market, only take the ones with 500mAh rating.

N-to-AA adapters come in handy: http://ogazent.com/cscart/n-cell-to-aa-b...pter-n-aa/



EDIT: Currently they're out of stock. Just email them and ask to have more made.

Dave

[Sylvain Cote]

(07-24-2016 11:47 PM)Dave Frederickson Wrote:  N-to-AA adapters come in handy: http://ogazent.com/cscart/n-cell-to-aa-b...pter-n-aa/

Wow!

That is better than my DIY solution using screws and nuts

Sylvain

[rprosperi]

(07-24-2016 11:47 PM)Dave Frederickson Wrote:  N-to-AA adapters come in handy: http://ogazent.com/cscart/n-cell-to-aa-b...pter-n-aa/

Thanks, I was just scrolling down preparing to ask Sylvain how one fits N cells into the (700) charger, which BTW I got on your recommendation. Good value, easy to use, though I'm not sure I've even figured out all the bells and whistles.

I too prefer rechargeable cells, but was answering smp about best source for the 41 bat pac (which I also use). The only bad thing about rechargeables is the relatively short 'warning' time when nearing end of charge.

[renif]

Choosing rechargeable cells definitely makes sense if the 41c is to be used on a regular basis. I used a DIY device similar to the one shown by Sylvain, albeit not as nicely elaborated. This works, although the adapters which Dave has found seem to be a more robust solution. In the past there was a real market of third party HP-41c accesories, also N size chargers. Alas, these devices made by the german supplier W&W are absolutely rare these days. I were lucky to get one from a friend in exchange for a well used 32sII. A very nice and reliable device which saved me money for many years. Regarding its simple construction (standard cell holders on top of a standard electronics casing) it should even be possible to tinker a comparable charger from a AA size model using appropriate N size battery holders. Of course, that would cost more than four ot those adapters shown above.

[Dieter]

(07-25-2016 12:01 AM)Sylvain Cote Wrote:  Wow!

That is better than my DIY solution using screws and nuts

There are other DIY-solutions – take a look at the picture in this 2011 thread on the old forum. ;-)

This thread also contains some more infos on using N-size NiMH-batteries like the GP50NH in processor-controlled chargers. The BC700 is mentioned there as well. Its 200 mA setting should be fine here.

Dieter

[Dieter]

(07-25-2016 09:10 AM)renif Wrote:  In the past there was a real market of third party HP-41c accesories, also N size chargers. Alas, these devices made by the german supplier W&W are absolutely rare these days.

Back in the Eighties a company named "Corvallis team" offered several accessories as well. Although they seem to have been specialized in HP41 software, there were also chargers, port extenders, special cases and much more.

(07-25-2016 09:10 AM)renif Wrote:  I were lucky to get one from a friend in exchange for a well used 32sII. A very nice and reliable device which saved me money for many years. Regarding its simple construction (standard cell holders on top of a standard electronics casing)

This looks like a standard charger for one or two 9 V batteries (6LR61). Their typical capacity (100...120 mAh for NiCds) is quite similar to N-size NiCds of the Eighties, so the charging current should fit. It should be mentioned somewhere on the back of the case. These devices usually offer no charging control at all, maybe at best there is a simple timer, typically set to 14 h.

(07-25-2016 09:10 AM)renif Wrote:  it should even be possible to tinker a comparable charger from a AA size model using appropriate N size battery holders. Of course, that would cost more than four ot those adapters shown above.

But you also get a much, much better charger. Consider the suggested BC700 which features decent charging control and short charging times in its default 200 mA setting when combined with 500 mA NiMH cells. However, do not try charging NiCds with such currents since their much lower capacity will result in a relative charging current that can and will damage these cells.

Nowadays a processor-controlled charger with a sufficiently low charging current (like the mentioned BC700 or IPC-1L), combined with 500 mAh NiMHs in AA-adapters, should be close to a perfect solution.

Dieter

[renif]

Thanks, Dieter, for sharing your insights in this matter and suggesting a more practical solution!

Of course newer charging technology should be used where possible. I keep the old W&W charger only because there is no need for a new one so far and, compact as it is, it also proved to be a lightweight compagnion on travel without taking care of spacers or other small adapter parts.

(07-25-2016 10:55 AM)Dieter Wrote:  This looks like a standard charger for one or two 9 V batteries (6LR61). Their typical capacity (100...120 mAh for NiCds) is quite similar to N-size NiCds of the Eighties, so the charging current should fit. It should be mentioned somewhere on the back of the case. These devices usually offer no charging control at all, maybe at best there is a simple timer, typically set to 14 h.

There are no ratings mentioned on the casing and I don't have a documentation either. But a quick measurement showed a stabilized charging voltage of approx. 5.4 V across fairly depleated cells. If i remenber correctly, there's a potentiometer inside the charger by which this voltage can be changed in a rather narrow range of 2 or 3 V.

Whenever this charger stops working, I definitely go for a processor-controlled device, just as you recommend. Again, thanks!

[Dieter]

(07-25-2016 01:28 PM)renif Wrote:  There are no ratings mentioned on the casing and I don't have a documentation either. But a quick measurement showed a stabilized charging voltage of approx. 5.4 V across fairly depleated cells.

If you measure the voltage between the battery contacts, this is the voltage of the cells (typically 1,2...1,45 V) which does not tell anything about the charging current.

(07-25-2016 01:28 PM)renif Wrote:  If i remenber correctly, there's a potentiometer inside the charger by which this voltage can be changed in a rather narrow range of 2 or 3 V.

If there is some kind of variable resistor inside it's more likely an adjustment for the charging current – or maybe the timer, if there is one.

Maybe you can measure the charging current? This could be done by removing one of the batteries, then reconnect it to the charger by the meter probes and an additional cable. Or you insert an isolating thin piece of plastic between a battery and one the charger contacts, with a piece of aluminium foil on either side so that you can connect the two leads of your multimeter. Should be something around 10...15 mA.

Dieter

[renif]

Your aluminum clip works great. Readout after some 2 h of charging: 2.05 mA (initially up to 5 mA), now slowly decreasing by roughly 0.01 mA/min. Single cell voltage (open circuit) approx. 1.35 V at that point. The charging is signaled with a green LED, which goes out as soon as the cells are full.

Hope that's the information you sought. Anyway, I think a modern replacement is to be set on the calculator budget plan at the end of the year...

[Dieter]

(07-25-2016 07:58 PM)renif Wrote:  Your aluminum clip works great.

Proven high-tech. <8)

(07-25-2016 07:58 PM)renif Wrote:  Readout after some 2 h of charging: 2.05 mA (initially up to 5 mA), now slowly decreasing by roughly 0.01 mA/min.

This sounds like a simple, unregulated charging circuit: more or less something like a resistor between the charger and the cells, so that the current is the voltage difference between these two, divided by the resistance. Since the cell voltage increases during charge, the difference decreases and so does the charging current. Technically, charging doesn't get much simpler that this. #-)

(07-25-2016 07:58 PM)renif Wrote:  Single cell voltage (open circuit) approx. 1.35 V at that point. The charging is signaled with a green LED, which goes out as soon as the cells are full.

I suspect the LED signal disappears as soon as the fixed charging time is over. Regardless how full or empty the battery is. I think it's safe to assume this low-tech charging circuit cannot detect when the batteries are fully charged. How should it, with such a low current?

Hmmm... assuming an average current of 2 mA, even an old Eighties-style 150 mAh NiCd N-cell would require a charge of roughly four days (!). Are you sure the current is really that low, i.e. 2 mA? Not more something like 20? Even the 1/2 N cells in the 82120A battery pack (approx. 70...80 mAh) were charged with approx. 15 mA.

Just to be sure: you set your meter to DC, not AC, didn't you?

(07-25-2016 07:58 PM)renif Wrote:  Hope that's the information you sought.

Yes, all this sounds like what I would have expected.
Except the charging current – should be much higher than 2 mA.

(07-25-2016 07:58 PM)renif Wrote:  Anyway, I think a modern replacement is to be set on the calculator budget plan at the end of the year...

Virtually anything will be an improvement. ;-)

Dieter

[renif]

After overnight charging, in Aurora's fresh light, I realized signs of leaking at one cell (pale-greenish salt-like residue on the plus pole). Certainly not in a condition to be placed into a 41c...
Probably an increased internal resistance explains the unexpected low charging current, which now is measured slightly higher at 2.4 mA (DC setting, cleaned plus pole). My budget plan grows by a set of rechargeable N cells, and perhaps the battery shield.

Thanks for your kind help, Dieter!