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Forum: µC & Digital Electronics P3 Motherboard only starts with cmos battery removed


von Halim M. (gmipf)


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My motherboard is a Gigabyte GA-6VXE7+ (rev. 1.0). Without a battery 
installed the motherboard starts and posts, I can enter bios etc. 
Everything seems fine. With a battery installed the motherboard doesn't 
react at all, no fan spin, nothing. The pwr header still has 5v but 
shorting does nothing. I need to remove the battery, turn off the psu, 
wait until the voltage on the pwr header drops to 0V. After that the 
motherboards starts again without a battery. To me it seems like a short 
somewhere when the battery is installed. I also have removed the battery 
holder and found some battery leakage which I have cleaned up, the 
traces below seemed ok to me there. My other theory is the diode which 
connects to the battery 3v line. The place where the rtc and cmos ram is 
located seems to be the southbridge VIA VT82C596B. I don't know how to 
go further, any ideas?

von ●DesIntegrator ●. (Company: FULL PALATINSK) (desinfector)


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did U ever reset the BIOS?

von Halim M. (gmipf)


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Yes, with its cmos reset jumper. Even started the board without the 
eeprom at all. Electrically it starts with the battery removed.

von Peter E. (Company: S&P) (eosangel)


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von ●DesIntegrator ●. (Company: FULL PALATINSK) (desinfector)


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Halim M. wrote:
> Even started the board without the
> eeprom at all.

and what does the board do w/o the chip?

von Halim M. (gmipf)


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Halim M. wrote:
> Yes, with its cmos reset jumper. Even started the board without the
> eeprom at all. Electrically it starts with the battery removed.

The holder is already removed. If i just touch +/- from the battery to 
its solder points the board will refuse to start.



●DesIntegrator ●. wrote:
> Halim M. wrote:
>> Even started the board without the
>> eeprom at all.
>
> and what does the board do w/o the chip?


it just starts as usual, fans spinning. But only with the battery not 
connected. No difference, except no beeping at all since no code is 
executed.

von Halim M. (gmipf)


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With just the battery connected but no psu i measure 0.6v on the pwr 
header. Is that behaviour normal? On an another board there is always 
0v.

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