Amp help, 6100 Bias to High

[siggy14]

So i installed some GT's in my Marshall 6100 and i goto adjust the bias. I have this probe thing i bought off ebay that measures in miliVolts DC. Basically it converts the amps to volts blah blah blah. Anyway two of the tubes are pretty much the same and then the other tubes one is close but the other is way off. Here is how they measure from the back going from left to right
52mvdc 34mvdc 29mvdc 29mvdc.
I am thinking maybe the resisters need to be replaced on the first two, what do you guys think, any suggestions?

Thanks,

Todd

[slo100]

Re: Amp help, 6100 Bias to High

It may be mis-matched tubes. Do you get the same readings if you swap around the tubes into other positions?

What resistors are you thinking of replacing?

[mm2002]

Re: Amp help, 6100 Bias to High

Do you have a problem with the amp or are you just trying to set the bias on it because you've been told you need to when replacing tubes? In my experience re-biasing for each new set of tubes is important for the purists but isn't really a neccessity (if the amp has a fixed bias at least run the same tube type). Some folks actually run un-matched sets (or even mis-matched brands) purposefully because it "dirtys" up the sound a bit.