41CV Fullnut shows "Memory Lost" consantly


I have tried all the reset techniques, and have even swapped out the CPU board. The calc works fine with other boards. The "memory lost" board looks to be the same as the first "C/CV common board" on Diego's CPU board page : http://www.clonix41.org/Maintenance/hp-41_PCBs.htm i.e. the one with blue electro capacitors.

Can anyone help please ?


Edited: 25 May 2011, 8:30 a.m.


If it can't be repaired, the machine is a perfect home for Monte's new CPU. :-)



It looks to be this one if I have the correct reference selected:

hp41CV/c common board, CV version:


1..does the Memory Lost occur when you turn it on?
2..once on does the Memory Lost remain displayed blocking
all key inputs?
3..once on can you then use the calculator correctly?
4..once on does the Memory Lost display intermittantly
interupting the correct use of the calculator?

Hazarding a guess, if 1 and 3 then the continuous memory appears to
be at fault. If 1 and 2, a faulty pca. If 4 a faulty continuous memory and connection to the pca.

If 1 and 3 then the blue electrolytic capacitors should be replaced. Someone correct me as I am away from home and my reference material. The larger capacitor is responsible for the continuous memory. As both are the same age I would recap both.

here is an excerpt from the HP 41C repair guide (this is from a 41C repair guide however the C1 capacitor still powers the calc in the off state):

If 1 and 2 the power control of the cpu may be at fault although maybe the capacitor again is at fault.

Cheers, Geoff

Edited: 25 May 2011, 6:41 p.m.


Yes Geoff, correct CPU board. I'm afraid it's a case of 1 and 2. and in fact even the on/off switch fails to turn the calc off. So I guess that means faulty PCA, which brings me to my next question, what's a PCA ? :-)

I guess C1 is the big one ?



Yes, the big one!

Printed Circuit Assembly, PCA, aka PCB. PCA is the term HP uses for the big board.

Now, if it is the board and the C1 capacitor doesn't fix it (they cost about 10 cents) then hold on to the calc. Marcus is correct, this is a perfect candidate for Monte 41CL board.

Cheers, Geoff


Thanks Geoff, I'll replace C1 and report back :-)



If you have case 2 after it is on, it is not a capacitor problem, its most likely a bad rom.

IMO, a bad cap is... unlikely.


Thanks Randy, you could well be right. I replaced the cap C1, and no difference in the behaviour - oh well.

Thanks for all the inup guys.


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