HP-41CV - doesn't power on

Everything about 41C 41CV and 41CX Hardware

HP-41CV - doesn't power on

Postby cappy2112 » Mon Jan 23, 2017 12:51 am

I've just received an HP-41CV and a few modules, for the cost of shipping.
The calculator is in very good condition- cosmetically, that is. I hope I can repair it.

I've installed a known good battery pack from another 41 that I use, but the HP-41 mentioned above does not turn on.
The contacts inside the calculator look very clean.

Would someone point me to some troubleshooting steps? I hope to narrow down which part(s) are bad, and decide to repair it
or sell it for parts.


Thanks

Tony
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Re: HP-41CV - doesn't power on

Postby wgh52 » Tue Nov 21, 2017 7:06 pm

Hello Tony and all HP-Fans,

I'm new to this forum and this is my first post. I am sooo glad to have found this site and forum as I do have the same problem with my HP-41CV: It stopped working today after working perfectly since ~ 1980 :shock:

The state of "play":
1. Switching "on" with a fresh battery pack yields a faint sizzling noise from the unit (which I never heard before!)
2. Hitting keys then sometimes produces a "beep"
3. In response to some key-strokes the display shows five high commas " ' ' ' ' ' " on the right side of the LCD display

All this seems to tell me, that there's still some life "under the (seemingly broken) surface" and it may be worthwhile to attempt repair.

Well, I have found a repair instruction post for the HP-41CX on this website which may be useful for the HP-41CV as well, but I'm not certain if the functional issue I face with it would be covered or mended by that major repair effort.

So, if anyone has had any good or bad experience with repair of an HP-41CV not powering on, I'd be extremely greateful for any answers and useful hints :!: :!:
IF I succeed in making my "beloved" Calculator work again, I plan to post a documented repair report with pictures in this forum.

I just cannot belive / accept that my HP-41 CV should be "gone" :roll:

Thanks!
Winfried

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Re: HP-41CV - doesn't power on

Postby cappy2112 » Tue Nov 21, 2017 9:54 pm

Good luck getting a reply on this website.
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Re: HP-41CV - doesn't power on

Postby rprosperi » Tue Nov 21, 2017 10:58 pm

wgh52 wrote:Hello Tony and all HP-Fans,
So, if anyone has had any good or bad experience with repair of an HP-41CV not powering on, I'd be extremely greateful for any answers and useful hints


The symptoms you describe could be due to loose posts (or the broken boss at the bottom of the well that holds the screw head for the 2 upper screws), though they also could be from other problems, but checking the posts, and repairing if needed, is the first step to take.

Some advice for disassembling/reassembling the 41:

1. Use a full size Philips screwdriver, not a jewelers size, hobby size, etc.

2. Turn the screws slowly, carefully and pay close attention to their progress into and out of the threaded posts/mounts.

3. Make sure the center bezel (between the upper/lower case halves) is oriented properly when you close the case, it only fits correctly one way.

4. When closing the case, hold it as tightly closed as you can, and again, screw them in slowly, watching progress until tight, DO NOT OVER TIGHTEN. This is a good time to have an extra set of hands, if a friend or patient wife/child is available.

It's annoying to repeat so much, but most posts/boss/screw damage is caused by people over-tightenting the screws.

Good luck with the repairs, and please share your results.
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Re: HP-41CV - doesn't power on

Postby wgh52 » Mon Nov 27, 2017 6:04 pm

Hello "rprosperi",

sorry for the delayed reply! The forum did not flag your available answer to me despite me setting the correct options... Anyway, thank you soooo much for posting such a useful answer :!: So far only battery and rubber feet are removed ;) , but I'll continue disassembly soon, following your instructions, and take a look inside...

On the site a larger repair is described, where e.g. PCB connections would be rebuilt. I'll consider that if your method does not resolve the issue.

I'll be back with a repair (progress) report including pictures and would appreciate your further comments.

Thanks for the encouragement!
Regards,
Winfried
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Re: HP-41CV - doesn't power on

Postby wgh52 » Mon Nov 27, 2017 6:17 pm

Hello "cappy2112",

cappy2112 wrote:Good luck getting a reply on this website.
This seems to mean I should not expect an answer as you or someone else did not get an answer. The guy may be incapable to answer these days now or actually may be got bored to death by the thousands of (repeatedly similar) requests over the past many years. Fair enough! It was worth a try! At least I did receive a reply that "the message was dispayed on the recipient's device". For what it's worth... 8-)

Cheers,
Winfried
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Re: HP-41CV - doesn't power on

Postby Garth » Mon Nov 27, 2017 7:06 pm

wgh52 wrote:Hello "rprosperi",

sorry for the delayed reply! The forum did not flag your available answer to me despite me setting the correct options.

Your "Notify me upon replies by default:" was set to "No." I changed it to "Yes" for you.

Garth (admin)
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Re: HP-41CV - doesn't power on

Postby wgh52 » Tue Nov 28, 2017 4:34 pm

Garth wrote:...Your "Notify me upon replies by default:" was set to "No." I changed it to "Yes" for you... Garth (admin)
Thanks Garth!

I appreciate your help! A notification about your last reply did not reach me either, though :? Well, it doesn't matter too much, I'll check in regularily :)

Cheers,
Winfried

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Re: HP-41CV - doesn't power on

Postby wgh52 » Tue Nov 28, 2017 5:26 pm

OK folks,

Part 1 of my HP41CV repair report.

Disassembly


After removing the 4 rubber feet 4 screws were loosened, the back cover lifted. and coveres removed:

Image

Looking into the void between the upper and lower PCB it became obvious, that there only was partial contact between them by the flexible contact rolls (no image of that, hard to take a picture, sorry), so I removed the the upper PCB and the flexible connection roll(s):

Image

This gives access to all connection pads and also (sadly) obviated that the lower right fastening pole is badly broken (i.e. horizontally and that broken off part broke into two pieces a few moments later).

Contacts cleansing

Staying cool about that broken pole I've now first proceeded by cleaning all contactpoints with a mild nail lacqer solvent (had good experience with that in other gold on gold contact problem cases).

Image

This is where I stand now. Next step is the repair of the mounting pole and then reassembly of the unit to see if we have progress or success already.

What I actually have at hand is an "Ethyl-2-Cyanacrylat" glue which I hope will do the job as it helped well in other plastic glueing cases which needed to provide mechanical stability... Any more hint, warning and/or advice would be much appreciated!

Kind greetings,
Winfried

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Re: HP-41CV - doesn't power on

Postby wgh52 » Tue Nov 28, 2017 6:23 pm

I couldn't stop right there as I found:

Repairing the broken Post:

Well, actually glueing / pairing the post turned out to be no viable option :shock:

Image

Three small cracked pieces just go beyond my handcrafting skills to reassemble/glue :oops: So, we need an alternative approach and rather fortunately, the post cracked at the end of the original screw length, so about 3mm intact Post length are left:

Image

So, if I can get a screw fitting the available depth, I'll very probably be able to build up the necessary contact force on the cracked side when reassembling the case. So, next stop is the screw dealer :P If the relative positioning of the "sandwich" is stable enough will have to be seen, a potential position stabilizer should be easy to make, maybe a washer fits. We'll see what's necessary; I'm still confident it can be done.

To be continued...
Cheers,
Winfried

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Re: HP-41CV - doesn't power on

Postby cappy2112 » Tue Nov 28, 2017 7:35 pm

wgh52 wrote:OK folks,

Part 1 of my HP41CV repair report.

Disassembly


After removing the 4 rubber feet 4 screws were loosened, the back cover lifted. and coveres removed:

Image

Looking into the void between the upper and lower PCB it became obvious, that there only was partial contact between them by the flexible contact rolls (no image of that, hard to take a picture, sorry), so I removed the the upper PCB and the flexible connection roll(s):

Image

This gives access to all connection pads and also (sadly) obviated that the lower right fastening pole is badly broken (i.e. horizontally and that broken off part broke into two pieces a few moments later).

Contacts cleansing

Staying cool about that broken pole I've now first proceeded by cleaning all contactpoints with a mild nail lacqer solvent (had good experience with that in other gold on gold contact problem cases).

Image

This is where I stand now. Next step is the repair of the mounting pole and then reassembly of the unit to see if we have progress or success already.

What I actually have at hand is an "Ethyl-2-Cyanacrylat" glue which I hope will do the job as it helped well in other plastic glueing cases which needed to provide mechanical stability... Any more hint, warning and/or advice would be much appreciated!

Kind greetings,
Winfried

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Thanks for this info.
What happened to the images?
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Re: HP-41CV - doesn't power on

Postby wgh52 » Tue Nov 28, 2017 7:39 pm

Still could not hold my hands still - just HAD TO check :twisted: if looking for a longer screw will mean repair success! So I assembled the thing as is (missing the one screw) and ...

TaaaDaaaaaa!!!! This god damned bugger lives!

Image

...just needs some encouraging pressure on the lower left corner (where the screw is currently missing) and it works!

So, this simple,longer screw shall not be a road block to final success! There will be a solution!

To be continued...

:D Cheers,
Winfried

PS: I can already say now: Never give up easily on an HP!

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Re: HP-41CV - doesn't power on

Postby wgh52 » Tue Nov 28, 2017 7:48 pm

Hey "cappy2112",

cappy2112 wrote:...What happened to the images?

Ooooopppsss??? The images are all PNGs and display well on my IE and Firefox browsers - even when quoted in your reply :? No idea why you don't seem to see them, they're posted on a picture hosting service site in Europe.

Regards,
Winfried

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Re: HP-41CV - doesn't power on

Postby cappy2112 » Tue Nov 28, 2017 8:13 pm

wgh52 wrote:Hey "cappy2112",

cappy2112 wrote:...What happened to the images?

Ooooopppsss??? The images are all PNGs and display well on my IE and Firefox browsers - even when quoted in your reply :? No idea why you don't seem to see them, they're posted on a picture hosting service site in Europe.

Regards,
Winfried

0008


Why do they need to be hosted anywhere?
Why not just attach them to these posts?
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Re: HP-41CV - doesn't power on

Postby wgh52 » Tue Nov 28, 2017 8:22 pm

Because I may use them otherwise as well.
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Re: HP-41CV - doesn't power on

Postby wgh52 » Tue Nov 28, 2017 8:35 pm

OK. Let me pracitce ;)

1 Dissassemble 2.PNG
Disassemble 1


1 Dissassemble 3c.PNG
Disassemble 2


2 Cleansing.png
Cleansing the connections/connectore


Tedious - 3 Pictures limit :cry:

Continued next Post...

Winfried

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Re: HP-41CV - doesn't power on

Postby wgh52 » Tue Nov 28, 2017 8:39 pm

4 cracked Posts.PNG
Destroyed Post parts


5 Screw length 1.PNG
Identify max. screw length
5 Screw length 1.PNG (35.27 KiB) Viewed 110222 times


6 Test 1.PNG
It works with Thumb pressure without missing screw


Hope this is visible for everyone now.

Cheers,
Winfried

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Re: HP-41CV - doesn't power on

Postby cappy2112 » Tue Nov 28, 2017 9:00 pm

wgh52 wrote:
4 cracked Posts.PNG


5 Screw length 1.PNG


6 Test 1.PNG


Hope this is visible for everyone now.

Cheers,
Winfried

0010


These ar evisible to me.
Not sure why the website is filtering the linked ones.
That's one for the admin
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Re: HP-41CV - doesn't power on

Postby rprosperi » Tue Nov 28, 2017 10:48 pm

Winfried:

For contact cleaning, I recommend DeOxit brand contact cleaners (Red for cleaning, Gold for preserving/long-term). Acetone (your nail polish remover) can damage all plastics and even some board materials. I've read it can also damage leads on PC boards, but that seems like an exaggeration to me, maybe others can confirm or refute that.

Most folks have reported poor results gluing vintage calculator parts using various types of superglue/crazy glue/other brands (all forms of cyanoacrylate).

2-part epoxies seem to have the best results, I personally have found JB-Weld "PlasticWeld" excellent. There are many flavors of even just this brand/type, with various color (black, white, putty/beige) and speed (of drying) options. For general purpose use, I typically use quick-setting, translucent yellow as it matches most places. For internal repairs, color likely doesn't matter.

It appears what's left of the post would be hard to glue back together, so it will have to be replaced.

One source of 41 repair parts is The Calculator Store, an online (excellent) website/webstore in Spain. Here is the 41 parts page:

https://www.thecalculatorstore.com/epages/eb9376.sf/en_US/?ObjectPath=/Shops/eb9376/Categories/The_HP41_corner

The parts from here are not cheap, and add shipping from Europe (assuming you're in US) and it's worse, however they have a good reputation and many folks have provided positive feedback about their parts and support. I have not used them myself, but I would not hesitate.

As a last resort, I can recommend an experienced repair service if you'd like, but hopefully you can get through the repair yourself.

Continued good luck!
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Re: HP-41CV - doesn't power on

Postby Garth » Wed Nov 29, 2017 12:05 am

Your pictures have always shown up correctly for me. No problem here. I have firefox running under Ubuntu 14.04 Linux and the Gnome Flashback Compiz GUI.
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Re: HP-41CV - doesn't power on

Postby cappy2112 » Wed Nov 29, 2017 12:57 am

Garth wrote:Your pictures have always shown up correctly for me. No problem here. I have firefox running under Ubuntu 14.04 Linux and the Gnome Flashback Compiz GUI.


I'm at work, it's posisble the IT dept has links outside the US blocked.
I'll try when I get home
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Re: HP-41CV - doesn't power on

Postby wgh52 » Wed Nov 29, 2017 3:16 pm

Hello HP41 fellows,

now it's the final stretch.

Final Assembly

Oh well, the screw dealer did not get into business with me because I thought of my other hobby: Listening to LP Records with magnetic cartridge pick-ups. I've found a matching mini-screw in my small fundus of cartridge fastening supplies which just does the trick to close the HP41CV case thoroughly even using the shortened/damaged post:

5 Screw length 2.PNG
5 Screw length 2
5 Screw length 2.PNG (57.27 KiB) Viewed 110679 times


So with this I went to putting it back together:

7 Final Assembly 1.PNG
7 Final assembly 1


To get the rubber feet fastened I'm using fresh thin double sided glueing tape and with this I seem to be done. The thing works again, so let's see how this repair last for the longer term.

In retrospect, just a little clarifying side-note:
rprosperi wrote:... Acetone (your nail polish remover) can damage all plastics and even some board materials...
The cleanser I used was explicitly stated "acetone-free".

So, thanks for all the useful hints and information!
I hope this repair documentation will come in handy for some other HP-41CV users suffering sudden "outage" of this brilliant calculator!

Best Regards,
Winfried
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Re: HP-41CV - doesn't power on

Postby JClovesHP » Mon Jun 03, 2019 2:43 am

Thanks to everyone for these posts.

My beloved 41C has been dead for a while, and today instead of doing other things I probably should have been doing, I Googled, found this thread, and tore into my dead 41C. Being I appreciate this community for its help, I wanted to give back and quickly post my "quick and dirty" solution to this problem.

Sure enough, after reading this thread, I realized my "lower right post" was broken. Now, I had no glue handy. And, I was not sure glue would hold anyway. But, I did notice the screw seems to secure. And, as noted in this thread I think, applying some pressure to the corner when assembled would bring my 41C back to life. So, I decided maybe just a little more pressure in that corner will just be enough to keep things connected and running.

So, I took two 3X5 cards, cut out a little squire with a notch to go around the post, and inserted it as shown in the picture I'm attaching. I picked two 3X5 cards for thee thickness factor. I pondered cutting up a plastic, "credit card like" gift card I had sitting on my desk, but felt that might be a little too thick. I also picked the 3X5 card as it, of course, will not conduct or cause problems with the circuit board.

After inserting and reassembling, my 41C is alive! It's alive!!!!!

I hope this helps someone in the future who's 41C sorrows are as sad as mine were.
Attachments
HP41_RepairWithPaper.JPEG
Picture of 3X5 Cut Out Inserted
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Re: HP-41CV - doesn't power on

Postby wgh52 » Mon Jun 03, 2019 3:28 pm

Hello JC,

thanks a bunch for sharing your repair idea!

Regards,
Winfried
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Re: HP-41CV - doesn't power on

Postby leg63 » Thu Aug 01, 2019 11:30 am

Hi everybody,

I had a similar problem. My old 41cx begin working erratically one year go. Display went off but on again when pressing on the bottom left of the plastic cover. Opening it, I discovered that one plastic post (bottom left) was broken. I therefore use a similar trick than that reported in this post (using a little longer screw to get into the remaining thread).

So far, so good. But, one month ago, the machine stopped working completely. An inspection showed that three of the four posts were broken (I suspect that, at a point, I tightened the screws two much...).

In this case, there were no remaining threads and hence no means of assembling the two parts of the body :cry:

The only solution I could think of was making the screws traverse the two parts so that assembling could be carried out using nuts and bolts.
The bolts could be hidden in the holes which were holding the head of the screws on the backside.
A rough estimation showed that the head of the respective screws would emerge above the "Sigma+" "div" and "." keys.
There was an unknown however : since the main PCB cannot be removed, I had no idea of the damage(s) I could create when drilling the holes.
There was also the possibility that the PCB is a multi-layer one, so that the hole can actually break a buried connexion.

But since there seems to be no alternative, I decided to have a try.

I used screws with diameter 2 mm and length 18 mm (for the two bottom posts) and 22 mm (for the upper one).
The corresponding bolts just fit in the holes provided on the back side for the screw heads.

My first attempt was unsuccessful : no display at all when powering on :cry: :cry:

But then I discovered that the piece of plastic holding the battery connector was tilted. So I had to glue it.
I took the occasion to add another dose of contact cleaning spray - WD-40 - on the main contacts.

And YES !

hp41cx.jpg


The "Memory Lost" message I got at power on was the cheerest one I've ever had !

Of course, I admit that, from of purely aesthetic point of view, the operation is debatable. ;)
But at least it works.

I would not recommend it unless there's no alternative. The probability of irremediably damaging the machine is high (I might have been very lucky when drilling the holes in the PCB..) [and of course, as usual "I should not be held responsible of any damage... " You're doing this at your own risks].

Anyway, I wanted to report this experience because it shows that when all seems to be lost, there's sometimes hope ;-)

Jocelyn
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Re: HP-41CV - doesn't power on

Postby leg63 » Thu Aug 01, 2019 1:51 pm

[Update]

I've just discovered that some replacement parts do exist for broken upper and lower posts (see https://www.thecalculatorstore.com/epages/eb9376.sf/en_GB/?ObjectPath=/Shops/eb9376/Categories/The_HP41_corner for ex.).

I wish I'd been aware of this before :/

Anyway, this means that the risky operation described in my previous post is probably not worth trying unless you like living dangerously ... or like the very special look of the repaired piece ;)

Jocelyn
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Re: HP-41CV - doesn't power on

Postby wgh52 » Thu Aug 01, 2019 3:24 pm

Hello Jocelyn,

thanks a bunch for your report and for the store link! Looks very useful!

One Question though:
What is the difference between the "half nut" and the "full nut" version?
How do I identify which one I need for my unit?

I hope someone can help.
Thanks and Regards,
Winfried
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Re: HP-41CV - doesn't power on

Postby Garth » Fri Aug 02, 2019 4:13 am

wgh52 wrote:One Question though:
What is the difference between the "half nut" and the "full nut" version?
How do I identify which one I need for my unit?

See this post.
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Re: HP-41CV - doesn't power on

Postby wgh52 » Fri Aug 02, 2019 7:03 am

OK thanks Garth!

So as my unit is a 1979 model and has square display corners, it's quite definitely a "fullnut".

Regards,
Winfried
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