Qt application on Photonav

Photonav internals

I learned this when repairing few devices:
TP1=1.3V core voltage
TP2=3.3V io voltage
TP3=~4.2V battery or usb or charger voltage
TP4=2.4V memory voltage
U8=rear speaker amplifier, chip unknown, markings A16852 812CA1 L59421, few devices had fried this
U18=LM3658 Dual Source USB/AC Li Chemistry Charger IC for Portable Applications, looks like USB isn't fully connected. If it would it should charge at same speed as autocharger. Chargerate is set to 500mA. Battery is about 1500mAh.
U19=LTC3406 1.5MHz, 600mA Synchronous Step-Down Regulator in ThinSOT, markings doesn't match, maybe copied chip. Set for 3.3V. Often fried
U21=same as above, set for 1.3V, few fried