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HP 41CV repair - constant Memory Lost message - Printable Version

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HP 41CV repair - constant Memory Lost message - Nigel Bamber - 08-20-2009

I eventually got the materials in order to put a permanent repair to my CV with cracked and broken posts. With some further help from Geoff and following his excellent guide , I managed to repair the posts and the case screws back on successfully. That is the good news.

The bad news is that I have a constant Memory Lost message. I cannot turn the calculator off and it responds to no key presses.

Can anyone help ? I assume its still a contact issue only this time it seems I have the 'reverse problem' to the one I had before the 'repair'.

I had to remove the logic PCA and the silk screen sheet underneath it to repair the broken post. So have I damaged something ?

I await your good ideas.

Nigel




Re: HP 41CV repair - constant Memory Lost message - Geoff Quickfall - 08-20-2009

This has happened with my half nuts but I am sure it can happen to the fullnut.

Hopefully it is a software, not hardware problem.

It took 48 hours for my two 41CXs to drop the MEMORY LOST lock up. Here is what I did and I am sure others have their methods, but do it in this order and move to the next step if the previous step failed:

1   try a master clear,  ON+CLX

2a if you have a card reader
b install it
c try to run a card.

3a remove the batteries
b short the far left to far right battery contacts
c reinstall batteries
d test with the ON+CLX

4a remove the batteries
b reverse their positions in the holder,
c install pack with reversed batteries
d hold the ON key ON for ten seconds then release
e reinstall batteries
f test with the ON+CLX

5a remove the batteries
b reverse their positions in the holder,
c install pack with reversed batteries
d hold the ON key ON for ten seconds then release
e leave calculator OFF over night.
f reinstall batteries
g test with the ON+CLX

These methods were first developed with Synthetic applications, which when handled incorrectly caused a freeze. The freeze was carried even when the calculator was OFF by the capacitor which retains the last memory condition of the software.

The above, all attempt to zero the capacitor leaving the calculator in its original state.

Mine took me to step 5 and I had written both of them off until two days later when I got back from a trip. I picked one up for the curiosity fully expecting it to remain in the OFF condition or with the frozen MEMORY LOST. Put in a battery pack, switched it on and VOILA! it worked. Tried the second machine and it worked!

Be warned, some have reported that it took up to a week without the batteries to unfreeze the calculator.

Hope this helps, Geoff


Edited: 20 Aug 2009, 7:18 p.m.


Re: HP 41CV repair - constant Memory Lost message - Nigel Bamber - 08-21-2009

Thanks Geoff. I'm on Step 5 , so let's wait and see. It would seem that the prognosis will be good (in the end).