HP-41CV - doesn't power on

Everything about 41C 41CV and 41CX Hardware

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 618 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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