Confused Solarus 40 watt transformer with mid boost switch

[MusicFox]

Hello. I have a Sunn Solarus 10/69 that I'm working on. After much searching here it appears likely I have a 40 watt output transformer but 6550's came with the amp. And a 7199 inverter tube. I have not plugged in yet pending cap job and variac available...Confusing....Will I have to rewire anything to use EL 34's again? In other words was a socket rewire neeeded to run the 6550's by whoever did it? Can I use the 6550's safely with the 40 watt transformer?. (transformer model 28 1-340) Confusing also is the Mid boost switch. I thought this was on 60 watt models of the 70's only.... Transitional model? Help me please Identify my output transformer..... numbers.. 28 1-340  followed by 606927  3 1/2" tall X 3"X4"

Thank You
Dennis Fox 

[loudthud]

If the 7199 is original, your amp is a 40W. The 606927 is consistant with a 1969 model. There shouldn't be a problem going back to EL34s. The only difference in the wiring is that EL34s require pin 1 be grounded, pin 1 is connected to the metal base on some 6550s and isn't used on some. 6550s can be run safely with the 40W transformers. Is there a small piece of paper glued inside the head box near the power transformer? It will have a diagram of tube locations and give the original tube types.

[MusicFox]

Tube chart was missing that's why I'm asking. THANKS for responding. I know much more now. I suppose rebiasing for el 34's would be in order if I switch back. I wonder what really happens when 6550's are used instead of el34's? Does wattage really go up? Even with original smaller transformer? and what is affected by smaller transformer? Tone?. Risk? I will be looking hard for these answers as some are very general but any help with "SUNN 0)))" specifics are greatly appreciated. I have read a bit about this being done, using 6550's in place of EL 34's (Not other way round). Component changes may be needed if bias pot range insufficient. I have since original post discovered evidence that 40 watters did indeed have boost switches in head version. So  less confused. I guess the 7199 Inverter is the right one (Chassis date 10/6/69) and good thing too I have 2 other spare 7199's (Telefunkens that test good) Best news is most resistors have been replaced (Cap job coming) and I got it for $50 Canadian. I may be able to get the 2 X 12 cab too but its covered in paint slops from garage storage.  Thanks again for responding
Dennis Fox 36 year musician

[loudthud]

The wattage may actually go down slightly with 6550s, maybe from 40 to 35 watts. The gain will go down with 6550s so you will have to turn the volume control a little higher to get the same volume. Bias should be looked at any time output tubes are changed. 6550s can be biased hotter and people generally say that gives a warmer sound. Funny how those garage stored cabs seem to attract paint.

[MusicFox]

  AWESOME.... Thanks I'll do some deep reading now that I know what I have.