I was told at one time that those stand-up resistors are bleeder resistors to bleed off the voltage stored in the caps after the unit has been turned off. Don't know if that's the whole idea of them being there, but that's what I was told.
Larry
Wouldn't a bleeder resistor go to ground to drain the capacitor it's hooked up to?
I just gazed at the schematic for the LK48B. And the first resistor,(20 ohms, 10W) comes off pin 8 from the rectifier to the first cap. The rest are dropping resistors for decoupling of other sections of the circuit...none go to ground.
That's an interesting idea. Are you saying that more heat is evolved than predicted by ohms law? It's common to add a 100R resistor to older amps between the rectifier and the first cap of the CRC to account for the higher mains voltages on vintage EL-84s which can run close to the plate voltage limit. I can't recall any of those resistors operating at excessively warmer temps than expected.
Well, I can't defy Ohms law...like I said, I'm guessing.
I rebuilt a Altec 345A PP EL34 stereo amp, and was dealing with trying to beat down the PS DC voltage like most vintage tube amps.
The Altec amp uses a pair 5U4s for rectifiers, with a 20 ohm 20W Standee type resistor between the rectifiers and the first capacitor.
I figured I could drop some voltage with the first resistor, and had a Standee type 70 ohm 25 watt resistor. The 20 ohm R dropped about 3-5 volts...not much. The 70 ohm only dropped 10 volts. So it isn't a voltage dropping resistor.
It was still a lot less voltage drop than I wanted.
I emailed a friend and ask about using a higher value resistor, and guessed to what it's actual purpose is.
My guess: The 20 ohm 20W resistor sops up some of the inrush current from the directly heated rectifier tubes to help the first capacitor.
His reply: Or more likely to limit the repetitive peak charging current to within the tube's rating. And went to mention using a higher value resistor will lower voltage and decrease the PS regulation.
Also to make sure when using a larger value resistor, that it is well within it's dissipation limits. If below the dissipation rating, it could be a fire hazard.
Other than that, I'm over my head...