I found a website that sell Mesa fsw and -according to them- I have the correct Lead/Rhythm fsw:
http://mesa.stores.yahoo.net/prepwrftsw.html
The fsw is also used on Mesa Caliber series amps.
So, it must be that the fsw I got is faulting.
Just used search to find this thread. cool.
My Studio Preamp came to me 2 weeks back with only a Reverb fsw, with no LED fitted, buts its a genuine Mesa one; looks old and grotty on the bare metal of the box. The Reverb fsw will also change Lead/Rythym channels ok. The selector button on the...
I just joined up because google found me this thread -i have just revd my first SP and its got JJs throughout. I asked my fatherinlaw if he had any old valves in his den (he's oldschool radioman). "Oh, I have old ones somewhere... " So I'll report back soon. Could be anything down there.