As ripple current is not sinusoidal but pulsed and is specified as RMS value, a true RMS meter would be fine.measure voltage drop across that. Can I use my old 'scope to do that?
That would be cap inrush current. It only happens once and is typically of no concern with tube amps as the PT limits inrush current to safe values.Re peak, turn-on, so, suppose amp has been sitting for some time, and the caps are "empty". Turn the on-off switch "on", its that first spike that comes across the transformer and hits the filter cap?
Trobbins is speaking about peak VOLTAGE at turn-on. Before tubes are fully heated and draw current there may be a voltage overshoot.
The switch arc only happens when contacts are opening (not when closing) and current is interrupted. The magnetic energy involved is too low to noticeably increase ecap voltage.Is this due to the on/off switch arc that occurs just as the contacts are about to close
If you mean the magnetic turn-on surge current, this is only a primary side effect. No related surge at the secondary.power transformer charging?