41c with 785 registers?

[Nate Martin]

I am rebuilding a HP-41 from scrap parts. I have gotten it to power up and it shows "memory lost" and immediately goes into program run mode. Holding down R/S shows "00 REG 785"

Has anyone seen something similar to this or can shed any light on this issue? My gut feeling is fried CPU board.

[Hans Brueggemann]

nate, please respond to PM _by email_

thx,
hans

[Pieru]

Hello.
Just arrived on the forum, with the same question. Old post !

I’ve found a hp-41cv in my father’s home.
Just running in prgm mode, showing a ‘flying goose’ on left digit, prgm flag is on.
R/S stops the program for 1 sec, showing 0, E00 then MEMORY LOST and starts again.
R/S then SST shows 00 reg 785, prgm flag is off. Then any other keystroke displays the function symbol + or resets the calculator.
Hard reset shows MEMORY LOST and prgm starts again.

I’ve tried to discharge the backup capacitor : unsuccessfull.

Any help would be appreciated.
Thanks

[mfleming]

I've seen somewhat similar behavior with 41C/CV models. It seems to be the result of poor electrical connection between the CPU board and the main PCB. One way you *might* be able to confirm this supposition would be to place the calculator on a flat surface, press down on the sides near the bottom row of keys, then power the calculator on. You may first need to reset by pulling the battery pack and shorting contacts.

Pressing the calculator case halves together causes the CPU board to press down upon the flexible zebra connector, which may temporarily establish a better conductive path. With or without a positive result from this test, you will likely need to open the calculator for cleaning and possible repair of broken posts. There are quite a few threads in the forums detailing how to do this type of repair, particularly in the old Articles section.

Let us know how things turn out!
~Mark

[Pieru]

Thanks for the answer.

I previously cleaned contacts, flexibles pcb, looking for corrosion. (I’m engineer in electronics).
Nothing. Contacts are good.
I swapped the board with an hp-41cx (my one). Without problem in the cv case.
Same problem with the cx case, the cv board behaves misfunctioning.

I’ve unsoldered the + pin from the backup capacitor. No more success after resoldering it.

Seems to be bricked ?
Unfortunately, it’s not easy to check the board when in case, with keyboard and batteries...