Toshiba Tecra 8000 cmos batteries

[jakdedert]

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

 

[Dave Dunfield]

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)?

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

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?

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...

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.

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

 

[jakdedert]

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

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