Please advice me how to do 5150 combo bias mod

[Kwm488]

Hi

I want to mod my 5150 combo. I find out the schematic is different with 5150 amp head.

Please see the schematic, is this 47k a bias resistor?
If yes, I should choose 22k or 47k trimmer? And what value resistor ? 10k?

And I want to add 1ohm resistor to the power tube pin, to check the ma. I did it for vintage Marshall. How can I do it?

Thank you

Is img_8451.jpg

[Jazz P Bass]

And keep in mind that the 5150 was deliberately designed with a lowish bias in mind.

If you goose up the current it messes with the 'Resonance' control.

[The Dude]

And keep in mind that the 5150 was deliberately designed with a lowish bias in mind.

If you goose up the current it messes with the 'Resonance' control.

Agreed. IMO, there is nothing to be gained by this mod.

[Dave H]

I'm sure you are right. I've deleted my suggested mod.

[g1]

Agreed. IMO, there is nothing to be gained by this mod.

How about reduced tube life?
(I'm sure the tube dealers would disagree with you)

[Enzo]

Yeah, if you are not wearing out a set of tubes every few months, you must not be rocking.