Brilliant 👏 Short and exact. Just what I needed. You should put this part in the doc with the other assembly instructions.VC190 trimmer capacitor is for tuning the RTC. For adjusting the VC190 you would need to have an oscilloscope or a frequency counter.
The aim is to make the Y176 crystal oscillate at 32768Hz frequency.
I tune the timmer capacitor as follows:
1. Keep the motherboard powered off when trimming the VC190.
2. Place a CR2032 battery to the battery holder.
3. Connect the oscilloscope probe to U178 pin 17 and ground the probe to GND on the motherboard (for example by connecting it to U178 pin 9 or motherboard's mounting hole).
4. Check what the oscilloscope says for the frequency.
5. If it's something else than 32768Hz, turn the VC190 clockwise or counter-clockwise till you get 32768Hz. After that the tuning is complete.