MESA BOOGIE NOMAD HELP (valves)

[Al M]

i just gotta mesa nomad 100, and i check the back of it tonight, i think there is somehting rong. 2 of the power valves are hot, glowing yellow with blue bits and the other 2, one is just glowin slightly yellow and ythe other seems dead. have the valves packed up? aparently its only just been revalved!

any help muchapreciated


Cheers

Al M

[microdmitry]

What do you mean exactly by saying "glowing yellow"? If plates are glowing red or orange - the amp might be screwed. This indicates high quiescent current going through the tubes, which is not typical for Mesa (they bias the output tubes a little cold). Alternatively, the tubes might have been damaged during transportation.

Orange glow inside tubes is normal, this is how they work. And they have to be hot to operate. A little of blue glow indicates low vacuum - you'll probably have to replace the tube that has blue in it soon.

I'd buy some replacement tubes (MATCHED QUAD!!!), because sooner or later, you'll need them anyway. Buy only matched tubes. Poorly matched tubes might not sound good.

Replace all four tubes, flip the power switch, then, after 30 seconds, the standby switch. Look at the tubes. They should glow orange inside. If their plates turn red - turn off the amp IMMEDIATELY and go to a good amp tech for repair.