Tube Question??

Discussion in 'Amps and Cabs [BG]' started by reasonbass, Jul 27, 2003.

  1. Hi, I just got a brand new Mesa 400+ and when I turn it on stand by the tubes glow normal. But when I take the stand by off the tubes start to glow with a blueish tint. I think I read somewhere that this was bad. So I was wondering if anyone can help me out.

  2. JonB


    May 27, 2003
    This sounds pretty normal.
    When you have the switch on standby, only the filaments are being heated with no other voltages in the tube. Put the switch in normal position, and B+ voltage, probably 400 to 500 volts is being applied to the plates. This causes some ionization of trace amounts of gas in the tube, giving a faint blue glow. Sometimes, it is just visible on the inside of the plate, and sometimes the whole tube has a violet glow, but will still be a good tube. It's bad if it has a bright blueish-pink glow, or if the plate(s) (the big grey cylinder-thing) are glowing red.
    If you have any doubts, have a technician check the tubes and the bias voltage to make sure you're not damaging the amp.
    You might want to get a bias meter so you can check this yourself. It comes in handy when you retube, too.
    Hope this helps.
  3. My 400+ does the same thing.

    I just accept it as looking incredably cool. my tone is better than ever, and all my power is there, so i can't complain. I'm pretty sure the blue glow is natural.

    Doesn't it look like the back of your amp is on fire?!!?! Looks sooooo cool!

  4. Yeah it does look I havent had time to crank it yet because everything in my house shakes and rattles. I had paintings falling off the walls! I love it.:D
  5. erikwhitton

    erikwhitton Guest

    Sep 20, 2002
    Portland, ME USA

    When I first got my 400+ i turned it to about 5 and felt like i could shatter every window in my building if i went too much higher!
  6. Dudes, I have another question here it goes:

    Can u use the slave out as a tuner out? I tried it and it worked. But I don't know if it will damage the amp in any way. I only tried it for a little bit.

  7. Rockbobmel

    Rockbobmel Supporting Member

    Check with your owners manual. I can't find mine. I use a tuner before the amp anyway. They usually have mute switches for silent operation.
  8. The GE 6550's in my vintage svt glow blue, looks cool and sounds great. I have even had some of the drive tubes glow blue (Brimar and Tung Sol black plate 12BH7's).