Toshiba Tecra 8000 cmos batteries

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- jakdedert
  
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posted
16 years ago

Thu, Dec 27, 2007 3:49 AM

Symptom: after coming out of storage of only a few months--totally dead. No lights, no sounds, absolutely no indication that a charger, a docking bay or a battery (all known good) are connected at all...a brick. This particular (peculiar?) dinosaur has two batteries attached to the motherboard.

First question: why two batteries (one 7.2 volt 40mah, one 2.4v unit--both NiMH's)?

Secondly, any reason why the 7-8 year old 2.4 volt unit still reads

2.4v, while the 7.2v piece is totally dead? Or should I instead be surprised that either worked at all?

Third--and probably most importantly--would that one dead (7.2v) battery cause the symptom? I don't know how much more time I want to put into this relic, but I can spring for a battery if that's likely to fix it.

jak

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- Dave Dunfield
  
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posted
16 years ago

Thu, Dec 27, 2007 2:00 PM

Who knows - one for CMOS clock, one for soft-controls? really depends on the design...

Perhaps the 7.2v has enough current being drawn from it to fully discharge it more quickly (which NICAD/NIMH really don't like). Perhaps one better quality - perhaps luck of the draw...

NICAD/NMIH have a tendency to go "short" when they die from old age, and it may be keeping some low-power "always on" circuit that detects the various external events you described powerless...

I had a Sony VAIO which had the same problem - internal nicad went completely dead and it would not power up at all. Seems the battery is required to recognize the soft-ON button. Once I replaced the battery it was fine.

If you want to make sure the battery is the problem, try replacing it with a 1000uf or so electrolytic capacitor - should charge up quickly and store enough power to get the machine started - that worked on my Sony machine.

Dave

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- jakdedert
  
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posted
16 years ago

Thu, Dec 27, 2007 6:58 PM

Thanks, Dave. I guess it's worth a shot. The battery is available for around ten bucks if one shops carefully. I hadn't thought of the idea that it might actually be rechargeable. The fact that it's probably shorted is germane, and easily checked. It's not just the 'buttons' don't work, but the unit is totally dead. The lights that fire up when it's off, but plugged in, don't even come on. A short in a charging circuit might help explain that.

Will report back....

Anyone else have an idea, or experience with this particular--or similar--unit? Research seems to indicate that this arrangement (multiple cmos batteries) is common with several different makes/models.

jak