My mesa 400+ make iisssssshhhgr iishhgr

[nepee]

There is a strange sound coming out from my amp when I don't play it sound like iiiiissssssshhhgrgr iiishhgriishhhgr iiiii... you know what it can be ?

[JoeDaddio]

Have you tried the amp with a different cab? My 400+ was doing some weird things and making some weird noises and then it popped a fuse. I replaced that and everything went back to normal, although I see an expensive re-tubing in my somewhat near future.


joe

[nepee]

Yes I tried different cab, different bass, different wire, different input and different volume... the input 2 make more often that sound... this is strange... same original tubes for 5 or 6 years but I don't play often with the amp... You think it's tubes ?

[chaosMK]

How high are you running the Master? Check to make sure your effects loop and secondary channel are both at 0. Check graphic eq too. I usually just fool around with stuff until I can insolate the problem.

[nepee]

master is around 3, the effect loop is close and the secondary channel is sometime close sometime open...the eq is open

[Ewo]

I wonder if the noise when the amp is idling might be RFI... When playing, it would be masked.

[Passinwind]

Originally Posted by nepee

...the eq is open

What do mean exactly by that?

[Green Lantern]

What did Boogie Tech support say? I would guess one tube blew. Do you see the nice soft orange glow on each power tube? The brighter orange means it needs to be replaced soon. I had the 400+ and I also did not use it much but the turning on and the turning off with changing in temps made it that he tubes needed to be replaced. With Boogie tubes there is no bias needed as you get all tubes with the same color code for them. He pre amp tubes last longer than the power tubes. Hopefully you won't need to replace them all. What a killer smooth sound that amp has. Still miss mine.

[anderbass]

Originally Posted by nepee

Yes I tried different cab, different bass, different wire, different input and different volume... the input 2 make more often that sound... this is strange... same original tubes for 5 or 6 years but I don't play often with the amp... You think it's tubes ?

Try plugging your bass (or even just a cord) into your effects return jack. This will disconnect/bypass the preamp section, so It'll help diagnose if the problem is being caused by the preamp or poweramp section.

[Red Planet]

Sounds like a bad preamp tube. You can pickup 12ax7's at your local music store. Buy one and replace V1. If the noise still persits then put the old tube back in V1 and swap the new tube into V2. There are only 3 preamp tubes in your amp. V1 is the one closest to the input jack, V2 is next and then V3 is last/furtherest from the input jack. Turn the amp off while replacing tubes.

That will be $59.95 please.