Strange T-Verb Tube Bias Readings with Bias-Rite

[mbmesa]

Hi, I just got a Weber Bias-Rite for setting the Bias on my other non Mesa amps. For kicks I measured the Voltage and Cathode Current on my T-Verb DR. Something looks very strange to me.

On Spongy and tube Rectifier: 350 plate Volts and 9 ma cathode current.
On Bold and Tube Rectifier: 420 plate Volts and 13 ma cathode current.
On Bold and SS Rectifier: 450 plate Volts and 20 ma cathode current.


The volts look fine for 6L6s but the cathode current is way low in my opinion. I know Mesa's are biased "cold" but this is out of spec for 6L6s isn't it ? 20ma should be at the low end not the high end of the scale.

The tubes are not fresh but even old tubes would not drift so bad out of spec would they ?

Any of you check your bias readings ? What did you get ?

 

[dennq45]

My old Fender Twin amp has a fixed bias and is at 21 ma. My Mesa RKII is the about the same. Biased cold for sure. I run my Riveras at 38 ma.

 

[mbmesa]

I am trying to determine if my numbers are within spec or is my Bias-Rite malfunctioning. 13 ma at 420 Volt is commonly considered in "crossover distortion" territory according to some of my research on this forum. I should see my lowest number not less than 17-20 right ?

 

[domct203]

Your measurements seem about right for the Recto Line. My 3-ch Triple was drawing about 23mA @ 460 Plate volts in Bold/SS (with Mesa "YEL" 6L6GC Tubes).

I think the bottom line is How Does It Sound / Perform? Mesa has been building some great amps for a long time, and they (recto's) are all biased the same.

Don't get so hung up on bias measurements. You'll spend more time tinkering, and less time enjoying the amp. I spent alot of money in the past on power tubes because I was more hung up on bias readings than sound quality.

Just my .02