OK now that you know it's the socket, It is likely something relatively simple and inexpensive.
A common problem with some model Mesa's (and other amps, too, for that matter) is a burnt or otherwise disconnected screen resistor. When there is no voltage on the screen, the tube will run at much lower current (power). This reduces the blue glow, but some sound still comes through. So.....next question.....
Is there no sound? :?:
If not, it's another problem related to that socket, but not too likely to be very expensive. Worst case is an Output Transformer issue, and that is really not likely at all so don't loose sleep over it....wires corrode and break....components fail that won't cost much to fix.
Get it to reputable tech and it can usually be fixed for minimal cost. (A resistor may be 50 cents!).
Labor is the main cost, and you may wish to call around to see what various shops charge for minimum labor. Some may want an hour minimum, but some will charge by 15 or 30 minute increments.
Either way it's a good amp (I have 2 friends that have Nomads and they are nice) so it's worth fixing and then you will have something to be proud of. :mrgreen:
As always, Good luck!
