Tube Amp Help!

[MarcusProg]

Hey everyone. I'm using a Mesa Mark V, and while jamming out with it, I was noticing a very strange hum, quite unlike the usual hiss from having pedals in the chain. I tried turning the amp off and on again, and shortly thereafter, the sound returned. After about a minute, my amp just went off. This is my first tube amp, so I'm still unfamiliar with the necessary maintenance that they need.

So my question is: What just happened to my amp? Is it a blown fuse or something?

 

[Vostre Roy]

Looks like a failed tube in the power amp, best is to contact the Mesa Boogie Tech Support, they'll pobably give you the things to check.

Here's some guideline from the website, might help you locate the problem, but to me it sounds like power tube failure

Mesa Boogie FAQ Page - Frequently Asked Questions

 

[Albionic]

if i had to guess with the current info i'd say a tube went down then blew the fuse. A mark v is a complex beast and too expensive to poke around in without the proper experience so i'm afraid its off to the tech with it.

 

[Vostre Roy]

Oh yeah, don't play inside the amp if you don't have electronical knowledge. Amps are dangerous

 

[MarcusProg]

Looks like a failed tube in the power amp, best is to contact the Mesa Boogie Tech Support, they'll pobably give you the things to check.

Here's some guideline from the website, might help you locate the problem, but to me it sounds like power tube failure

Mesa Boogie FAQ Page - Frequently Asked Questions

Thanks!! I'm gonna check this out. I'll also see if I can give Mesa a call. I was looking at some troubleshooting on other sites, and I'm wondering if it's the fuse that blew.

 

[celticelk]

Amps are dangerous

"Dangerous" here having the value "COULD KILL YOU." Seriously. Take it to a tech.

 

[MarcusProg]

"Dangerous" here having the value "COULD KILL YOU." Seriously. Take it to a tech.

I've read that before. Don't worry! I haven't even touched the guts of this thing in the time that I've owned it.

 

[Vostre Roy]

"Dangerous" here having the value "COULD KILL YOU." Seriously. Take it to a tech.

Yeah, in the future I'll try to use the term "deadly" instead of "dangerous", might illustrate more the level of danger inside

 

[titan amps]

if there is a blown fuse, it doesn't mean that the fuse is the problem. fuses are put into circuits to protect the big, expensive to replace bits from the cheap to replace bits. in this case, it's likely protecting the output transformer from the power tubes. just replacing the fuse *could* cause more problems.

best bet is to call mesa and follow their recommendation.

 

[Given To Fly]

Mesa's customer service is top notch! They will go to great lengths to help solve a problem on amps out of warranty, so considering you have a Mark V, they will take care of you!

 

[MarcusProg]

Alright, so I feel like a total noob for not knowing this earlier. I was fiddling with the back panel on the Mark, and found the bias switch selector (I bet some of you are gonna cringe at this) and switched it from 6L6 to EL34 thinking that it would switch between two different sets of tubes (I'm an idiot for this, I know.) and that's when the humming started happening. Based off of what I read, the incorrect biasing was applied to the actual tubes within the amp, which were 6L6s, causing the fuse to be taking more power than it could withstand, or something to that degree. I saw that this was the problem, changed the bias back (it just had a little switch), and replaced the fuse. The tubes and other guts of the amp seem to not have taken damage, which is great.

Thanks again for your help, everyone.

 

[Fretless]

Yeah, in the future I'll try to use the term "deadly" instead of "dangerous", might illustrate more the level of danger inside

Well dangerous describes it better than deadly in my opinion! I survived getting electrocuted by an amp, I may have heart trouble now, but I lived! (and yes I do have a lot of electrical experience, it was a complete accident that I touched the part that I did when I touched it, long story)

 

[Vostre Roy]

Well dangerous describes it better than deadly in my opinion! I survived getting electrocuted by an amp, I may have heart trouble now, but I lived! (and yes I do have a lot of electrical experience, it was a complete accident that I touched the part that I did when I touched it, long story)

You can also cross an highway blindfolded and get to the other side unnarmed, doesn't mean that the risk wasn't deadly

Potential risk remains deadly. You have great chance to survive a shock from an amp, but the risk to get a deadly one is still there.

I took one also. Way my Traynor is made, I put my finger by mistake on the standby switch pole when I wanted to turn it on while the cover of the amp was not on...

 

[trenolds39]

So are you running 6L6's in the power stage?

 

[MarcusProg]

So are you running 6L6's in the power stage?

Yes. They're the stock power tubes in the amp.

 

[MESA Boogie]

By running the amp with the bias select switch set incorrectly - a small change in voltage to the control grid produces a large change in the amount of current flowing. With more current flow the electrons overrun the control grid and excess current flows to the plate. This is a mild short, and what caused the hum. The fuse blew acting as a protection device. Hopefully the output tubes were not stressed too much - best of luck!