[popcornmix]

Is there a way to check power supply during livetv with voltmeter?

You can measure the 5V on the Pi2 itself. See here.
E.g. between pin2 and pin39 of gpio header. Do this when system is under load (e.g. running with advanced deinterlace and suffering from corruption issues).

You may be able to find somewhere on the s660 to probe. E.g. the pins on the USB socket here which would be a little more accurate as there will be some voltage drop from the USB cable.
A low quality cable between the Pi and s660 could make voltage drop problems worse.