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Mesa 400+ problems !! RED HOT Lamps !!

Discussion in 'Amps and Cabs [BG]' started by 2001-Ps, Sep 28, 2008.

  1. 2001-Ps


    Dec 31, 2007
    Quebec, Canada

    In the last few weeks I had my 400+ blowing it's 8 amp fuse after the lamps went red hot while playing. I cant ID the actual problem & help is welcomed on this issue...

    Here's the set up...I use mostly P basses (passive) going through the Channel 1 (for active basses) channel volume set at 7 with master volume at 2. Amp settings like: bass 6, mid 10, treble 7, going through 2 x 8 ohms Mesa cabs, one 2 x 10s & one 1 x 15.

    I use the following effects:


    Tech 21 Prog DI (overdrive)
    True Grit (overdrive)
    Big Muff
    Boss Tuner
    Boss Flanger
    (the Ibanez Tube Screamer isnt used anymore)

    I mostly use the overdrives but not combined. Either I go for the True Grit or one of the settings on the Tech 21. On few occasions I'll combine one of these with the Big Muff.

    What is causing that overload on the lamps ?? They go red hot (like if they were going to explode) and if I dont shut it down at that point the fuse blows...

    The standby switch make a small tik when you push it on-off. Probably needs to be replaced but could this be the cause of the problem ??

    Am I overloading the amp too much with those overdrive pedals ??

    Had a gig last night...Tried a different set up: plugged in the Channel 2 (passive) volume at 2, master volume 2. Same effects used....We had 2 x 1 hour sets & it worked fine....(but I was stressed as hell in the event it would fail as I dont have a spare 400+ head to back it up...)

    Help is greatly appreciated.....For sure it'll go to a tech. for a complete check up...Thanks, Mk
  2. Your amp has an internal malfucnton and NEEDS tech attention. It's not the signal you're feeding it. Take your amp to a qualified repair tech.
  3. Red Planet

    Red Planet

    May 29, 2005
    You have my friend a common problem with those amps. I have had both the 400 and 400+ plus. By not having a Bias pot if the Tubes drift any they can end up redplating and run away.

    I suggest you call Boogie they are good about sending out replacement Tubes with this Problem.

    Talk to Tien and tell him Greg Beasley sent you.

    These amps like to do this every once in a Blue moon.

    It is not a bad problem or something that shoulgd make you get rid of the amp. It is a common problem with many tube amps. Sometimes it can happen even with the Bias set dead on what it should be.
  4. BurningSkies

    BurningSkies CRAZY BALDHEAD Supporting Member

    Feb 20, 2005
    Syracuse NY
    Endorsing artist: Dingwall Guitars
    I suggest that you follow PBG's advice. It doesn't sound like 'tube drift' to me...it sounds like a bigger problem.
  5. ...or you get the amp serviced by a decent tech who could install an adjustable bias control or at the very least bias the amp properly so you don't have to get a new set of tubes every few months.

    No one said to do that.

    No and no. That is wrong on both counts.
  6. Red Planet

    Red Planet

    May 29, 2005
    Red Plating is part of Tube Amps. It does happen deny it?
  7. Happens yes. Normal operating condition- NO! If your engine is still running but glowing, should you continue to drive it?

    Please say no.
  8. Cherryplating occurs when tubes conduct too much current because of too little bias. If bias is set properly and the tubes spec to the circuit, the plates DO NOT GLOW RED. Runaway happens in transistors, too. They don't glow; they just die.

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