HP-41CV - doesn't power on

[cappy2112]

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

[wgh52]

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

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"

Thanks!
Winfried

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[cappy2112]

Good luck getting a reply on this website.

[rprosperi]

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.

[wgh52]

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

[wgh52]

Hello "cappy2112",

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...

Cheers,
Winfried

[Garth]

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)

[wgh52]

...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

0004

[wgh52]

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:



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):



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).



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

0005

[wgh52]

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



Three small cracked pieces just go beyond my handcrafting skills to reassemble/glue 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:



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 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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