HP 34C - strange bug

[Michael Fehlhammer]

My HP 34C shows a strange behaviour: The low-battery-dot that appears at the very left of the LED is always on, also when fully charged batteries are inserted.
This is somewhat annoying, since I have no chance now to know when the batteries really are becoming weak.
Has anyone got an idea where the fault is located and what could be done to fix it?
By the way? I faintly remember that there was a discussion years ago about a thick book with many photos, a repair bible for the old calculators, soon to be released ... called THE book ... is this book available now, or has the project been canceled?

[rprosperi]

Hi Michael,

Is it possible that the batteries are older and not holding the full original charge (they should be 1.2V for NiCD)? I had this same situation in my 34C with batteries that held enough to use the machine for a while but they were old and just not going to original full capacity.

Geoff Quickfall announced, about a year ago, that he was planning to release THE BOOK as a free, 2-volume e-book (PDF I think) as soon as he wrapped up some loose ends. He wanted to get it out before starting on his PhD, and I think that was slated to begin in September, but it's likely that COVID-19 has delayed all that, just like everything else. I've not heard any plan update.

[Massimo Gnerucci]

(11-06-2020 06:34 PM)Michael Fehlhammer Wrote:  By the way? I faintly remember that there was a discussion years ago about a thick book with many photos, a repair bible for the old calculators, soon to be released ... called THE book ... is this book available now, or has the project been canceled?

[Michael Fehlhammer]

Hi Bob,
in this case I am sure that it's not the batteries, because a second HP 34C doesn't show that behaviour. Must be a fault in the electronics that detect low bat or drive the low bat indicator light, I am afraid.

(11-06-2020 07:08 PM)rprosperi Wrote:  Hi Michael,

Is it possible that the batteries are older and not holding the full original charge (they should be 1.2V for NiCD)? I had this same situation in my 34C with batteries that held enough to use the machine for a while but they were old and just not going to original full capacity.

Geoff Quickfall announced, about a year ago, that he was planning to release THE BOOK as a free, 2-volume e-book (PDF I think) as soon as he wrapped up some loose ends. He wanted to get it out before starting on his PhD, and I think that was slated to begin in September, but it's likely that COVID-19 has delayed all that, just like everything else. I've not heard any plan update.

[rprosperi]

(11-06-2020 07:45 PM)Michael Fehlhammer Wrote:  Hi Bob,
in this case I am sure that it's not the batteries, because a second HP 34C doesn't show that behaviour. Must be a fault in the electronics that detect low bat or drive the low bat indicator light, I am afraid.

Different units may have different voltage sensitivity, I would still try brand new batteries (if available).

Also, try cleaning the both the battery tops and the contacts with IPA. Even if not visibly dirty, this often helps.


p.s. I LIKE Massimo's small, subtle emoji...

[Michael Fehlhammer]

small and subtle, indeed! :-)

Thanks for the tip, I will try out new batteries and clean the contacts.

[Massimo Gnerucci]

(11-06-2020 07:59 PM)rprosperi Wrote:  p.s. I LIKE Massimo's small, subtle emoji...

It started as a classic emoji, but time flies, and it grew up... day after day.

[Dwight Sturrock]

Did you try alkaline batteries? I always used alkaline in my 34C after the original batteries died and I had no issues. The higher voltage may turn off the battery low light.

[Michael Fehlhammer]

Hello Dwight,
thank you for the tip, I will try this out.