Hi, I own a BFSR (anno 1966) recently I discovered that the anodic voltage is 500 Volts when stand by is off
And only 438 Volts when Stand By is on, or when Tubes 6L6 are out from the sockets.
Could, please, someone tell me if it's normal such drop or there'is something wrong.
P.S. lately the sound was becoming weak though I replace the 6L6s with two new brand tubes.