My 29C's even more bizarre behaviour


Hello all.

First off, thanks for helping me with my many questions about my 29C. But, if I may,

what would cause

1--program memory to lose contents and replace program stems with random keycodes?

2--turning on the 29C to start up with 'Error'

3--pressing keys in RUN mode to cause random digits to appear in the display

and, here's the most peculiar.

4--removing the battery pack for several hours and then reinserting the pack to cause the 29C to function properly, back in working order

only to have the process repeat again if after I've put the 29C away for a week or so?

Any thoughts?

Edited: 24 Apr 2012, 7:23 p.m.


There is indeed a technical term for that. It's called "broken".

It sounds like a bad CMOS RAM chip, a fault in the power supply circuitry, or both. If you're very lucky the ACT chip might be OK, but it's quite possible that it has failed also.


Well. In that case, could it be that the 29C is just too old? Are Woostocks known to decay in performance and chip stability with age?

Edited: 24 Apr 2012, 8:24 p.m.


That's possible, but it seems more likely that it was damaged at some point by the battery charger.

The chips will fail on their own eventually, but for CMOS chips that takes a long time unless they were defective in manufacture, or operated at high temperature for an extended time.


Hi Matt,
This may be a long shot, but just be sure the battery contacts are good and clean. My 29C will exhibit bizarre behavior if the all the battery contacts aren't squeaky clean...this includes the spring in the far end of the battery pack unless you have a spot welded strip connecting the cells. I polish everything with a pencil eraser then clean with an alcohol soaked Q-tip. I'll keep my fingers crossed for you.

Regards, Hal


Hello all.

Thanks for going through this with me. I must confess though. Although I sometimes 'beat a dead horse' with some of my issues I post here (e.g. that 50G Equation Writer question a few days ago), it's because I'm very determined to solve questions I cannot figure out on my own (or the answer is so obvious, I overthink the problem) after SEVERAL hours of thinking in my own way. I tend to be hardest on myself that I should be smart enough to solve what seems to be a very simple issue. Another point is that I try to think 'outside the box' till I either exhaust myself or get a headache because I think I should be intelligent enough that a box of (forgive me) plastic and metal shouldn't outsmart me. It's like that old comparison of being so smart that someone can perform heart surgery but they can't fix a car (you know what I'm trying to say here).

Also, I'm very determined because I want to be able to take good care of my collection and when (my words) stupid carelessness or shortsightedness causes some of my items to go haywire, I never stop to think that perhaps the item was messed up before I got it. Or, if the thing is in working order in the first place and it gets bunged up because of my carelessness, I get mad at myself because I should be smart enough to have been more focused and careful !! in the first place !!

So, thank you all for your help, wisdom and patience with me.

Edited: 25 Apr 2012, 10:20 p.m.

Possibly Related Threads…
Thread Author Replies Views Last Post
  [WP34s] strange behaviour at number entry Dieter 12 3,643 06-06-2013, 05:36 PM
Last Post: Harald
  HP 39GII Undocumented behaviour Bunuel66 0 836 05-12-2013, 05:23 AM
Last Post: Bunuel66
  HP-29c keyboard dead 2nd row problem Xavier A. (Brazil) 6 2,274 07-17-2012, 07:09 AM
Last Post: Xavier A. (Brazil)
  HP-29C Counterparts Matt Agajanian 2 1,256 05-12-2012, 06:44 PM
Last Post: Matt Agajanian
  29C/25C question. Matt Agajanian 7 2,287 04-03-2012, 12:03 AM
Last Post: Matt Agajanian
  My very schizophrenic 29C Matt Agajanian 9 2,810 04-02-2012, 05:12 PM
Last Post: Matt Agajanian
  Help!! My 29C may need a doctor. Matt Agajanian 5 1,998 03-31-2012, 04:23 AM
Last Post: Ignazio Cara (Italy)
  Legible version of 29C Curve Fitting program Matt Agajanian 6 2,107 03-21-2012, 07:46 PM
Last Post: Matt Agajanian
  Sleek approach to Register Exchange on HP-29C Matt Agajanian 8 2,694 03-16-2012, 01:04 PM
Last Post: Marcus von Cube, Germany
  HP-70 erratic behaviour - first results Alberto Fenini 0 826 12-04-2011, 03:49 PM
Last Post: Alberto Fenini

Forum Jump: