My MK V is definately dead :{

mule#1 · Jan 28, 2012

Amp powers up. No glow in any 6L6 tubes but the 5u4 rectifier tube glows. 12ax7 tubes V1.2 & 5 glow but 3,4,6 & 7 don't. Put in 4 good power tubes and pre amp tubes that weren't glowing and nothing. And Mesa was not open on Friday.

What the heck could be wrong? Can V1 cause all those tubes not to work? I didn't replace that as it was glowing fine.

search4tone · Jan 28, 2012

mule#1 said:
Amp powers up. No glow in any 6L6 tubes but the 5u4 rectifier tube glows. 12ax7 tubes V1.2 & 5 glow but 3,4,6 & 7 don't. Put in 4 good power tubes and pre amp tubes that weren't glowing and nothing. And Mesa was not open on Friday.

What the heck could be wrong? Can V1 cause all those tubes not to work? I didn't replace that as it was glowing fine.

Just to cover all the bases have you changed the rectifier tube? This week I had problems with the 5Y3 in my other amp. All the tubes lit up but in my case it was blowing the fuse. When I called Suhr they said almost certainly the rectifier tube. I was told today's rectifier tubes are lucky to survive a few years.

mule#1 · Jan 28, 2012

I bought this brand new only 2 weeks ago!

purpledc · Jan 28, 2012

Yes a bad V1 tube will make you have no signal anywhere. Its your main input tube for all channels and if its fried you wont get anything anywhere. And whether or not a tube is glowing really has nothing to do with whether its working properly. Some tubes even when operating perfectly have little to no glow as the plate structure covers most of the filament that would be orange. Me persoanally If Im having tube issues my power tubes and V1 are the first things I look at. Did you check the fuse as well?

MrMarkIII · Jan 28, 2012

If the fuse is blown you'll get nothing at all - no power indicator light, no tube "glow", zip, zilch, nada.
Yes, tube "glow" means little. Tubes aren't designed to have any kind of consistent "glow". Is the tube warm? Then it's "on". Still doesn't mean it's working correctly.
The way to troubleshoot tubes is ONE-AT-A-TIME.
Otherwise, you will never determine which tube is bad.
Another "Is there gas in the tank" question:
Is an operating speaker cable plugged in and being used correctly?

mule#1 · Jan 29, 2012

I did check the fuse and it powers up. I dropped it off at my local authorized tech yesterday. I figured that would be easier than shipping it to Mesa and since it's 2 weeks old tubes and all are under warranty. He said it is more than likely something simple and my hope is its just a bad tube 0r something. I'll post back when I find out.