HP 41CV Interchangeable Main Board

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HP 41CV Interchangeable Main Board

Postby vervalin » Mon May 23, 2022 6:25 pm

I have an older HP 41CV (SN: 2123S11164) that has the main board from circa 1981 (it does NOT have any piggy backed chips). But nothing I do can make it come to life. I have done everything to try to make it work with no success. It worked for awhile and then one day I pressed the PRGM key and got a garbage display. From that moment it has degraded to the point that now the screen just remains totally blank. So, really my question is:

Are ALL the HP 41CV main processor boards interchangeable?

It seems like there were many, many versions of these processor boards that HP went through and I just want to know if I can pop in any old HP 41CV processor board and see if it will work.

Thanks!! Paul
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Re: HP 41CV Interchangeable Main Board

Postby BillBee » Tue May 24, 2022 11:17 am

To the best of my knowledge the CV/C boards can be swapped with a few exceptions - Tall keys IIRC - display driver (?).

I've swapped boards quite a few times and it usually comes down to the zebra, ribbon, posts or case backs. Or a pleasant combination of them. Looking around the case seam if there is separation then that would be a clue. display end - case back. Label end - posts.

It can drive one nuts so I hope for the best for you.

-Bill
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Re: HP 41CV Interchangeable Main Board

Postby vervalin » Tue May 24, 2022 1:04 pm

Thanks Bill, This is exactly what I needed to know. I have owned and actively used HP 41s since around 1981 and have even made processor board changes like increasing the clock speed on my first HP 41CV. I have just never had to swap the main board. All of the things you have mentioned are right on target. I'm pretty sure I've checked all that stuff but I will make another pass just to be sure. The "garbage" display seems to me to indicate that a chip has gone bad on the board and then ultimately no screen at all. Anyway, thanks again for the reply, knowing the C/CVs are almost always interchangeable with few exceptions is a great piece of information to have. Regards, Paul
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Re: HP 41CV Interchangeable Main Board

Postby BillBee » Tue May 24, 2022 5:01 pm

Glad I could help Paul.

The boards are pretty tough so I hope its just a connection issue.

Good luck and post a follow-up.

HP41 recovery success stories are great.

Bill
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Re: HP 41CV Interchangeable Main Board

Postby vervalin » Sun Sep 03, 2023 2:01 am

Hi Bill,

Sorry it has taken me over a year to reply to this. So, I shelved this CV for a long time as I could not find a solution. I ended up selling this unit on eBay "AS-IS" a few months ago. When the buyer posted his "feedback" after the transaction, he said "Thanks it was an easy fix". So, I reached out to him and asked REALLY, what did you do??? He said one of the solder connections that connect the display to the keyboard PCB had come loose. He hit it with a soldering iron and everything worked great. So, lesson learned. Check the little solder connections up by the display to see if any of them lift up easily. I am glad this HP 41CV was "resurrected" even if it wasn't me that did it!!!

Paul
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