1/2 power confusion

[johnnyfancy]

hi all, first time, long time. i've got a question about the 1/2 power switch on my markIII. it's a black dot fully loaded colliseum. it's not marked anywhere simuclass, but came with 6l6s and el34s. this may be a dumb question, but is the 1/2 power switch actually half power or does it drop it down to simulclass 15 watt or so? any response would be great.curiosity is killing me

 

[trem]

If it came with EL34s and 6L6s then it's probably simul equipped. To make sure, peek underneath and check whether the output transformer has a "562003" inscription on it.

If it's indeed a simul, then the switch is actually a "simul/class a" switch ie. when you select 1/2 power, it's actually class a, regardless what the face plate reads. And yeah, it should be 15 watts in that setting.

~trem

 

[MrMarkIII]

If you have both 6L6s and EL-34s, it's probably Simul-Class. Mesa was notorious for switches labeled "Half/Full Power" when they meant Simul-Class, 'specially on heads. Very common. Some will say the real way to tell is by checking the OT.
According to my 1984 catalog, the Simul-Class Coliseum has four 6L6s and two EL-34s for 150 watts. The non-Simul-Class is 200 watts with all 6L6s. Curiously, it doesn't say how much power is available in the "Half Power" position.
And yes, the photo shows the "Full Power"/ "Half Power" switch.

 

[johnnyfancy]

thanks for the replies. one tranny is labeled SD 19055
E1A606-401
the other is 0180322
E1A606-xxx344