Mesa mark V 90 shenanigans

[nandrewjackson]

I wanted to try and run 6V6 in the mark V 90.
Long story short, yes, it will run 6V6 in a couple of the power profiles.



Mark V 90 is made to either run a quad of 6L6 or a quad of EL34. It has a bias switch, 2 position,  6L6 or EL34.
It has 6 power modes.
2 global, "full" and "variac"
3 sub modes 10W, 45W, and 90W.
For a total of 6 modes.


I wanted to see if any of the modes could run a quad of 6V6 so I did a bunch of voltage measurements. 



All testing with FX loop hard bypass. No reverb tank plugged in. No footswitch plugged in. 8 ohm speaker connected to 8 ohm jack. Cooling fan on. GEQ on. All controls at half, except volumes at zero.


All mesa 12ax7s. Mesa 5u4gb. Matched quad of electro harmonix 6V6. 2 seperate pairs of 6L6, 1 pair mesa str440 grn, 1 pair "apex matched" JJ 6L6.


I used info from rob robinette "OT resistance method" for calculating plate current. Rob robinette bias calculator for percentage dissipation information. 


I haven't made the measurements with EL34s installed yet.


45 watt mode, only on channels 1 and 2 (not ch 3) can run on tube rectifier,  I was very disappointed to see the low % dissipation in tube rectifier mode  .

[nandrewjackson]

Data

[nandrewjackson]

Schematic
https://el34world.com/charts/Schematics/files/Mesa_boogie/Mesaboogiemark_v.pdf


Schematic shoes wrong tube designations for the 4 output tubes. The numbers I use in my data are from the circuit board.


Apparently there is a newer Schematic with corrections, not available publicly.