Subject: HP41 problem..

From: Jos Dreesen / Marian Capel <[email-masked]>
Date: Sat Mar 8 05:18:00 2003

My (unexpanded) HP41c developed a strange problem...
It still knows how to do the maths, but any value stored inside a register 
gets lost : i.e. 1234 STO 12, RCL 12 yields 0.000....

Any pointers ( also pointers to a more suitable group ? )

			Jos Dreesen

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From: Joe <[email-masked]>
Date: Sat Mar 8 07:10:29 2003

Jos,

    You have a bad Data Storage IC. Depending on which version board is in your 41 it may have from 1 to 4 DS ICs but they are custom built ICs made by HP specificly for the HP 41 so you'll never find one. Time to find another 41 for parts. There are plenty of htem out there that have broken displays, bad power supply ICs and/or corroded battery terminals.

   Joe

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From: [email-masked] (Tony Duell)
Date: Sat Mar 8 17:56:00 2003

> Jos,
> 
> 
>     You have a bad Data Storage IC. Depending on which version board 
> is in your 41 it may have from 1 to 4 DS ICs but they are custom built 

Didn't some HP41s haev 5 RAM (Data Storage) ICs? Each one 16 registers 
long (one for the 'status registers', 4 for the 64 user registers?

> ICs made by HP specificly for the HP 41 so you'll never find one. Time

A trick that works when you have a CV with one of the 'extra' DS chips 
failed (that's to say one of chips that hold registers after the first 
64), is to crack open a single memory module (which are really common!), 
then extract the 'PCB' and wire it inside the 41, in place of the bad IC. 
Solder the B3 and B4 lines to put it at the right address. Yes, it's a 
kludge, but it works. And alas it's not applicable in this case.
 
> to find another 41 for parts. There are plenty of htem out there that 
> have broken displays, bad power supply ICs and/or corroded battery 
> terminals. 

Perhaps I've been lucky, but I don't think I've ever seen a bad PSU chip 
in a 41. Bad CPUs I've had, though.

Damaged battery contacts can be kludged over with a bit of care, so 
that's not a reason to regard a 41 as a 'parts' machine...

-tony