Tube problem or not?? my amp is more broken.

Hey guys,

I flipped my amp on today, and the clean channel sounded really strange.. looked around the back and only one tube was lit up.. Mesa Rectoverb 6l6 *2 .. The other tube wasnt even getting warm.. but the fuse didnt blow.. im confused?

[thesedaze]

when you say one tube, are you referring to one of the powertubes? Which tube wasn't lighting up?

If it's one of the powertubes, could just be a bad tube...

[Blue Strat]

.....and that would certainly cause distortion at almost any volume.

Yes it is the left power tube.. it has like one TINY TINY little red ash and its not even where it should be its around one of the sides.. other than that its not lit up and not getting warm.. the other tube is glowing and also glowing a little blueish

[thesedaze]

Originally posted by ggarriso
Yes it is the left power tube.. it has like one TINY TINY little red ash and its not even where it should be its around one of the sides.. other than that its not lit up and not getting warm.. the other tube is glowing and also glowing a little blueish

then buy some new tubes, and rebias. have you ever changed powertubes for this thing before?

I bought the amp used, i was told they were changed about a month before I bought the amp so about 2 months ago.. I can change tubes though luckly (or unluckly) Mesas are fixed bias so no rebiasing is required

[JamesPeters]

Originally posted by ggarriso
Mesas are fixed bias so no rebiasing is required

Cough cough...

Just so you (and other) know, "fixed bias" doesn't mean "non adjustable". Lots of fixed biased amps have bias pots for adjustment.

As for whether the Mesas "need" biasing or not...you'll find widely varying opinion on that one.

Good luck with the amp!

[Peter C]

Originally posted by JamesPeters
Cough cough...

Just so you (and other) know, "fixed bias" doesn't mean "non adjustable". Lots of fixed biased amps have bias pots for adjustment.

Are you saying that Mesa's have bias pots?

(just checking as it would save me some money from having something put in that's already there...)

[Blue Strat]

Originally posted by Peter C
Are you saying that Mesa's have bias pots?

(just checking as it would save me some money from having something put in that's already there...)

Mesas don't have bias pots but, in general, that doesn't mean that they don't require rebiasing. ALL fixed bias amps require biasing whether they have bias pots or not.

In most amps that are fixed biased but do not have bias pots, you would have to enlist an amp tech to install a bias pot or change the fixed bias resistor to accomodate a particular pair of tubes.

In the case of Mesas, some dealers (including myself) can select power tubes that will bias properly in Mesa amps without rebiasing.

[John Phillips]

Before you do anything else, swap the two tubes round. This will tell you immediately if it's a tube or amp problem. Chances are it's just a dead tube, but it is just possible that there's some kind of broken connection on the tube socket.

If the dead tube stays dead in the other socket, it's just the tube.

Don't worry about the blue glow, BTW - that's totally normal.

I'm not going to get into the debate about biasing Mesas , but if it needs new tubes, either get a set of Mesa-branded ones, or ask Mike (Blue Strat) for some better quality ones that will run correctly without needing to rebias.

If you do need new tubes, change both but keep the remaining good old one as a spare - you never know when you might need it...