MIG100H Tubes

[Walt-Dogg]

Just picked up a MIG100 H and it's killer, but the power tubes glow blue when standby is off and glow orange when standby is on. I'm guessing this isn't a good thing, but the tubes are supposed to be pretty much brand new. I know an online message board isn't the best forum to get the answers I need but I'm not gonna learn anything by taking it to my tech until after he's gone through two other amps plus the MIG100 and having paid him for all his work.

[At_Giza]

I learned long ago to take every amp I get for a check up.

If I were you, I would hurry up and do that, because tubes aren't supposed to do that.

Relevant:

http://www.youtube.com/watch?v=mBym83g78NY

MiG 100 with its 6L6s going out.

[Walt-Dogg]

They're not doing anything like that. I'ma film it.

[At_Giza]

Well of course not, that's an extreme case of tube failure.

But so far as I know blue glow in a tube is abnormal.

[Walt-Dogg]

But so far as I know blue glow in a tube is abnormal.

Same here. It (EDIT) turns out that it's the tubes are most likely underbiased. I e-mailed my tech earlier and he responded to me a little bit ago.

[mckinnon audio]

   Hi there,the blue inside your tubes is gas,won't hurt anything,tubes should still work,just means they're old,or have a lot of hours on them.The red glow however,points to a bias problem,good luck,Mel.

[MammothVolume]

Red glow = redplating, it's pretty obvious once you see it. You'll think "Shit! That looks hot."


Turn off the amp.


When the amp is in standby, it's only the heaters that are being powered, once you flick the standby off, the rest of the tube jumps into action. That explains the difference in color.

[Walt-Dogg]

Yeah, my tech clarified yesterday that it's just the gas in the tubes. And the tubes are quite new actually. Thanks.

[tacklebox455]

Blue glow can be mercury vapor in the tube but more common blue shows that the tubes and or tubes have a very tight vacuum.