i have a stihl re 100 . it has a nozzle that spins round . it will remove paint if not careful with it . its mains powered but you might want a battery one .
voltage readings like what it is lead me to high/open resistors or cracked traces or poor grounding . a faulty capacitor might even be the culprit
did you try flexing the board whilst checking pin 19 voltage ?
unplug it from mains wall socket .. put your meter on 200 ohms scale then one probe to each pin of the mains plug . switch amp on and see what reading on the meter .
did you cut the spare pins off the relay this time ? still can't really understand why it would burn this way as it shouldn't connect to anything . all i can think is arcing because the pin is touching or very close to the chassis . and the contacts in the relay are very close together ,
sometimes its the start up capacitor . its a small one . also test the diodes on the cold side .
but firstly put the board back and warm it up with a hair dryer or similar and see if it starts up then .if it does it will be a bad capacitor