For tube sets clip the negative lead to ground, the
metal chassis.
Sams probably shows the 390 V as #1. That goes to
all the #1's on the schematic. The voltages may not be
exact as the set is not regulated. If its + or- 3% you are
usually OK. There is often a distribution chart that shows
how many places the sources go, that helps when tracking
down a short.
As far as an amp meter goes almost anything will do.
Keep in mind a cold set just coming on will draw a ton
of current & pin the needle for a second on some meters.
Hope that helps.
73 Zeno
