SVT Problem!! Please help me now!

[kranahan]

Alright... As straight-forward as I can be.

There was humming coming from my speakers. So I checked the back of the SVT. The bias control and lights on the right side were lit (one bias control light was lit green). The bias control lights on the left side were completely off. Nothing at all. I'm guessing maybe a power tube is done for? I have no clue.

Here is my current setup:

Furman Power Conditioner -> Ampeg SVT-CL (SLM) -> Neutrik Connection into a Mesa PH 610

Tried different amps and cabs and it is definitely the head. There is no humming when it is on standby. But once off standby it hums out of all speakers and the horn.

I find it weird the lights on one bias control are completely off?? Does this happen?? I have not touched or moved the bias controls at all.

I am able to play. The hum still stays while I play.

Help me please!!!

 

[kranahan]

Quick note: I already checked past threads and could not find anything on this specific problem

 

[B-string]

Chances are good you have lost a power tube on one side.

 

[kranahan]

Yeah I figured. But they all light up. Does that make a difference?

 

[B-string]

Sorry no, the tubes lighting up means very little. Look for a blue glow when striking a loud note. The tube not glowing blue is bad or something feeding it is bad, otherwise a tube tester is the only way to find it. (Note to all: Not mentioning voltage readings, scope patterns or things that can get you fried.)

 

[kranahan]

OK thanks. I will check that out right now.

 

[SanDiegoHarry]

not to be snarky... but when I saw the title of the thread, the first thing I thought was "yeah, you threw out your back! Now THAT'S an SVT problem!"

 

[kranahan]

So I did what you said... Played loud and here's what happened. 3 of them turned blue while the other 3 did not. I think that is because they are matched triplets, right?

 

[kranahan]

not to be snarky... but when I saw the title of the thread, the first thing I thought was "yeah, you threw out your back! Now THAT'S an SVT problem!"

I have almost done that too... but who hasn't!

 

[johnk_10]

So I did what you said... Played loud and here's what happened. 3 of them turned blue while the other 3 did not. I think that is because they are matched triplets, right?

sounds like its 'take it to a tech' time to me.

 

[B-string]

^ What johnk 10 said. Looks like a failure in the bias circuit possibly. New tubes will not help. Don't keep using the amp at this point, as you can cause more expensive damage.

 

[kranahan]

sounds like its 'take it to a tech' time to me.

If only I knew of any.... Time to look!

 

[B-string]

Look in the stickies under Good amp Techs you may find a recommenation in there!

 

[kranahan]

Alright. One more question. Should I bring my own tubes to the tech?

 

[JimmyM]

Certainly there's someone in the East Bay area you can take it to. Not like we're talking about Hooterville

 

[rbonner]

Certainly there's someone in the East Bay area you can take it to. Not like we're talking about Hooterville

Hello from HOOTERVILLE, Detailed photos to follow.

BOB

Oh you thought I was going to post BOOB shots again eh? This is a picture of where I live taken in 1866... I told you I live on the eastern border of the western frontier... My house is the one in the middle.

 

[kranahan]

I will show you! Driving the bumble bee through west o is not fun though.

 

[B-string]

Alright. One more question. Should I bring my own tubes to the tech?

You could if you wanted, but you may not need any. That is unknown yet as three tubes are not adding to the output. Keep your current tubes where they are, don't take them out or switch them around! It will only make the repair harder.

 

[kranahan]

I ended up switching the preamp tubes to see if that made a difference. The lights switched positions so it ended up being a bad preamp tube. I ordered Tungsol 12AX7 and put them in yesterday. They sound better than the stock sovteks. I am very happy I fixed the problem and made the head sound better with Tungsol tubes. Thank you for all the input.

 

[B-string]

Kudos on the self diagnostic, I suspect you found a bad driver tube.