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unsuccessful meaning it didn't work at all... I will check the solders again but I think they are all ok, passive test meaning without power on, so I wasn't testing voltage over a resistor, just checking that it was the value it is meant to be.

Okay, so I tried unsuccessfully to do a bias mod to my RK ser 1.... now I have returned all back to it's original specs BUT... I am having massive issues with a 'floating' bias voltage. I am getting readings of up to 300mV (before I quickly turn it off) across all 6 power tubes (only reading 1...

Cheers Bottle Rocket, thanks for the advice :D I have a roadking 1, the schematic is for a RK2. I don't have a V6. So this schematic is only a very loose reference. I thought the idea of these bulletins was to do your own tech work or at least consult with techs, PLUS the closest MESA tech is...

It's just that I wish to be able to bias individual pairs (each individual tube would be better) due to the switching the roadking does, not all 4 6L6's are in operation in all selected power amp linkages. I wish to 'fine tune' the 2 pairs separately and eliminate not having an exact matching...

So, no photo's yet, but I've looked over the schematics for the RK II. If you look at the power amp schem. pg 10. If I swap out the 220k resistors (directly off the 6L6 input) with trim pots will that give me independant control to the pairs of tubes?

Shall do Dom, I'll swap it out with a 22K trim pot and post some photos thanks heaps!!

I may be going about this wrong... :oops: I literally removed the resistors directly connected to pin 5 (see page 10 of the manual you linked). I thought this would give me individual bias control on each tube. Are you saying I need to control the overall bias to the pairs?? Should I return the...

Hi Dom, thanks for the welcome :D The Screen grid resistors are connected to pin 4 and are a decent sized chalky black, mounted in a gap in the PCB, for heat dissipation I'm assuming. Please correct me if I am wrong. The Roadking has a breakaway PCB with the tube sockets mounted to it, as...

Hi everyone, I am trying to mod my Roadking series 1 head so I can bias the tubes, I have removed the fixed biasing resistors attached to pin 5 on all the output tubes (4 6l6's, 2 el34's) and replaced with 2k trim pots. the R's were 1.5k for the 6l6's and 5.6k for the el34's - I added a 4.7k...