Backlight doesnt turn on, no sound, battery is at 3V. It was at 3.6 when i checked a while ago. When I try to charge at 5V the amps go between 0 and 0.2 in a loop. I checked for shorts and didn’t find anything wrong. I think its probably the cpu but I hope not. Any advice?
From my knowledge a dead SoC is showning ~0.45 A and is not looping around 0 and 0.2 A. And if the battery is loosing voltage from 3.6 V to 3 V without turning on, I’m pretty sure there is a short which cause the discharge.
Does the 5 V reach the m92 and the bq?
Does bq provide 4 V on the sys-line?
bq starts at 4.8V and then drops down to 0.5V before instantly jumping up to 4.8 again and repeating.
m92 seems to get 5V
Theres 2.8V on the sys-line from bq but the Battery is also at 2.8V.
I tried checking voltages without the battery and everything seems a lot more normal (5V on bq, 4V on sys) but theres a hissing sound coming from somewhere. i think its near m92 but not sure.
What does sys show only with battery without 5 V from usb?
sys is switched from the input. If battery is the source, it shows the battery voltage. If usb powered (5V/15V) it shows the max 4V.
With only the battery sys shows 2.81V, exactly the same as the battery voltage.
Ok. I assume atm that the bq is fine and the issue is towards the m92.
Are the 5 V at the down-left also jumping from 5 V to 0.5 V?
If you mean 510 its at 5V
The other voltages are also present, beside the top right jumping 5V (at 497mV)?
My board looks a little bit different to that schematic but i think its at 0V
Please check the other caps around the m92 with 5 V supply plugged in the usb port.
On the top right is maybe only one cap, but your fluctuating voltage should be seen here.
the small cap on the right, marked 627 at the top, has the fluctuating voltage. The diode? on the left next (756 at the bottom and oL at the top) to it has a fluctuating voltage of 10V to 0V.