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Memory Lost 41CV - Printable Version

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Memory Lost 41CV - Elio - 04-02-2004

My HP41CV displays "memory lost" even when I take off the batteries and put them back again. Does any one help me?

Re: Memory Lost 41CV - Vieira, Luiz C. (Brazil) - 04-02-2004

Hi, Helio;

in most cases, this sort of message appears when there is a bad contact between the keyboard's PCB and the calculator's mainboard (circuit board, where all components escept the LCD and drivers are assembled). Please, have a look at the image below:

Compare this image to your HP41's LCD and see if you can identify. It's more likely that it is a fullnut. In this case, what's written above is applicable, and in this case it's necessary to open the calculator and clean the contacts between the boards.

Halfnuts usually do not show this message this way, unless you have faulty components or a cold solder in one or more of the CPU's teminals.

The other possible (and very remote) case happend once with my old HP41C. Suddenly it did not do anything but showing a slightly blinking [MEMORY LOST], almost one blink at a second. In this case, the calculator was sent to HP in order to be repaired. It was necessary to turn the calculator against light to see the slightly blinking. It was a faulty RAM IC. THe fullnuts HP41C have two RAM IC's: one with 16 registers used by the system and another one with the 64 registers available for the user. Yes, we all "see" 63 registers, but there is a 64th. one that must provide 3 bytes for the permanent .END. and consquently let 4 bytes always available. This one cannot be a numbered register.

Let us know if you need guidance. Otherwise, Fix That Calc is always a second choice.


Luiz (Brazil)

Edited: 2 Apr 2004, 11:15 a.m.

Re: Memory Lost 41CV - Eric Smith - 04-02-2004

THe fullnuts HP41C have two RAM IC's: one with 16 registers used by the system and another one with the 64 registers available for the user.

Many HP-41C calculators have five RAM ICs (1LA7), all with 16 registers. One is for the status registers, and four are for the user. The 64-register chip (1LE7) was introduced with the HP-41CV, which used five of those for 320 user registers, and one 1LA7 for the status registers. The HP-41C continued to be manufactured using five 1LA7 RAMs until stock of the 1LA7 was depleted, then switched to one 1LA7 and one 1LE7 as you describe.

The 1LE7 was later replaced with the functionally equivalent 1LH5, probably as a cost reduction.

Re: Memory Lost 41CV - Vieira, Luiz C. (Brazil) - 04-03-2004

Hello, Eric;

thank you for adding these facts. I remember I saw some earlier HP41C motherboards, mostly those units with "top keys" (is it the correct term for those tall keys?). And I also remeber seeing the same motherboards in some earlier HP41Cv's as well. If I am not wrong, all RAM IC's are lined side by side in the "top" of the mainboard (the side that's closest to the LCD assembly), no "piggy back" soldering, right? One weird fact: the CX fullnuts have a mainboard arrangement that's even closer to these earlier C and CV's mainboards. (thank you , Renato...)

Man, I "love" having these "pictures" in my head and talk about them. Too bad I could not follow all of the HP41 "saga" when it happend. I "was" there, being time a reference, but I "wasn't" there, being place a reference.

Time to make things up, now.


Luiz (Brazil)