Backup battery discharged -> GTA01 and GTA02 dead

Rod Whitby rod at
Mon Jul 21 15:33:32 CEST 2008

Andy Green wrote:
> Somebody in the thread at some point said:
> | I'm measuring the voltage at the right end of the VB_SYS cap with a
> | voltmeter (I'm at home, so don't have a scope handy).  It seems to be
> | fluctuating between 3.7ish volts and 5V.  Does that give any clue?
> Sounds like the VB_SYS "trap" and the battery is not filling in enough.
> | Any other test points under the can that I should check?
> I can't recommend this, but what I would do is briefly short V+
> testpoint near USB socket (it is 5V from the host PC) to the +ve battery
> terminal nearest the edge (with no actual battery involved) and then try
> start up.  It'll probably die again a few seconds after, but you could
> stick a battery in by then at it should be OK.
> The reason I would do it the VB_SYS "trap" behaviour this seems
> reminiscent of comes if the battery is unable to smooth out the dip at
> startup for whatever reason, but usually the Host PC can provide 1A or
> whatever for a few ms that are needed.

Would using the official Openmoko charger be safer here, since it can 
provide 1A continuously?

Interestingly, with the can cover popped, this device booted twice in 
succession for the first time ever since it stopped working reliably.  I 
didn't try a third time, cause I was able to get into the NOR boot menu 
on the second boot.

-- Rod

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