CMOS battery replacement

Andrew Schenck andrew at
Tue Dec 22 01:35:33 UTC 2015

On 12/19/2015 9:27 AM, H. Nikolaus Schaller wrote:
> Hi,
> Am 12.12.2015 um 03:06 schrieb Benjamin Deering <ben_deering at>:
>> On Fri, 11 Dec 2015 15:38:54 -0800
>> Andrew Schenck <andrew at> wrote:
>>> That's a lot more work than I had hoped.  Thanks very much for the
>>> info though.  If I'm going to be soldering I might as well try to fix
>>> the USB port and GPS port at the same time.
>>> -Andrew
>>> On 12/11/2015 1:30 PM, Benjamin Deering wrote:
>>>> The backup battery (supercap?) is welded to its bracket and
>>>> won't push out.
>>>> I replaced the backup batteries in my GTA02s with supercaps several
>>>> years ago.
>>>> The parts I used didn't match the original footprint so it was a
>>>> little work.  If you get the exact replacement part, it would be
>>>> easy if you have soldering experience.
>>>> I vaguely remember a software problem causing the line that charges
>>>> the backup bat/cap not being set high.
>>>> Good luck,
>>>> Ben
>>>> On Fri, 11 Dec 2015 12:26:54 -0800
>>>> Andrew Schenck <andrew at> wrote:
>>>>> The secondhand GTA04 I have now is pretty beat up and can't charge
>>>>> because the USB port is disconnected.  I've been using a spare
>>>>> GTA02 as a charger, but every time I switch out batteries the
>>>>> clock resets to 12/12/1999 16:00 and it's a pain to re-set it
>>>>> since network time doesn't work.  I couldn't find any information
>>>>> on the wiki about replacing the CMOS battery to solve this
>>>>> problem; has anyone here dealt with this same problem before and
>>>>> have recommendations?
> The GTA04 already has a supercap in battery shape. They came to the market
> in ~2011.
> Since there is nothing to replace (a supercap rarely fails), it is most likely
> a software issue that the charging current provided by the tpw65950 is not
> enabled.
That's good to know.  I had foolishly assumed that the GTA04 used the 
same solution as the GTA02.
> So which OS&kernel are you using? In most systems I know, the RTC
> "resets" to 1st Jan 2000.
I'm using Radek's last QtMoko, v56  for GTA04, kernel 
3.7.0-gta04-qtmoko-v56.  The RTC *does* reset to 1 Jan 2000 0:00 but I'm 
at UTC -8:00 so it becomes Dec 31, 1999 16:00.   If I could trigger the 
tpw65950 manually via console every once in a while that would be fine 

>> I was successful in fixing the USB port, but never tried the GPS port.
>> The GPS port is under a lot of stress when the board is installed.
> Should not be the case. You should move the USB+GPS socket as flat as
> possible into or out from  the case. Then push out the case at the position
> of the headset connector so that the latter snaps down a little in its hole.
> This avoids breaking off connectors.
> See also photos in chapter 4 (especially page 18) of the GTA04 system
> manual:
>> I ended up giving up on the traces and soldering thin wires to the ESD
>> protection chip and to the leads on the jack.
> That is fine and indeed sometimes needed if a socket was broken off.
>> After getting the USB port connected electrically, I used JB weld epoxy
>> to fix it mechanically.  The repair lasted years including some pretty
>> rough use and being reflow soldered.
>> Good luck,
>> Ben
>>>>> I disassembled a GTA02 enough to see the battery, but it didn't
>>>>> yield to gentle pressure trying to slide out of its bracket and I
>>>>> don't want to destroy things too badly in my attempt to fix them
>>>>> so I didn't push too hard.  Because of this, I don't even know the
>>>>> exact type of button cell to buy to replace it.  Any help would be
>>>>> appreciated.
> The GTA04 original part is a PAS414HR-VG1.
> BTW: it should also work in the GTA02 (which has a real 3.3V LiIon cell
> in 414 package).
>>>>> Thanks,
>>>>> -Andrew
> BR and also good luck,
> Nikolaus
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