EL84 Getter Flashing Black???

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by BozoTone, Mar 8, 2006.

  1. BozoTone

    BozoTone Member

    Messages:
    557
    Joined:
    Jan 29, 2005
    Location:
    Nashville, TN.
    Just removed a set of EL84's out of my amp and one of the tubes getter flashing is black. What does this indicate? The other 84's flashing is the normal silver. This is matched set of 27 mA draw tubes that have 7 or 8 hours of playing time of which only the last 3 hrs. have been really driven. I have warmed these up good each time before playing them.....
    BZT
     
  2. BozoTone

    BozoTone Member

    Messages:
    557
    Joined:
    Jan 29, 2005
    Location:
    Nashville, TN.
    LOL...OK...is it safe to still use this tube? This set sounds vey good.....
    BZT
     
  3. donnyjaguar

    donnyjaguar Member

    Messages:
    4,243
    Joined:
    Nov 4, 2005
    Location:
    Canada
    I've seen this happen with tubes that were run too hot. They may still work for a while. The getter material is used to get rid of the impurities in the tube after the vacuum is created. If there's no silver getter left it can't get rid of the impurities any more.
     
  4. billdurham

    billdurham Member

    Messages:
    293
    Joined:
    Dec 29, 2005
    whats up with the "getter"? Not familiar with this term? Which part of the tube is it another name for?

    thanks
    BD
     
  5. rockon1

    rockon1 Member

    Messages:
    11,495
    Joined:
    Aug 12, 2005
    Location:
    Stamford CT

    Thats the "thing" thats usually(not always) at the very top of the tube. sometimes they are round shaped and called "halo" getters,sometimes more of a "d" shape, sometimes square like in some chinese tubes....
     
  6. Timbre Wolf

    Timbre Wolf GoldMember Supporter Gold Supporting Member

    Messages:
    8,824
    Joined:
    Oct 14, 2005
    Location:
    Berkeley, CA
    Actually, the getter is the often silvery coating inside the tube. Some call this getter flashing (as BozoTone did). The halo-/D-/square- is really a getter wire, from which the getter material is deposited on the inside of the glass during manufacture.

    Sometimes "healthy" getter flashing is black, sometimes it has rainbow refractions, but most often it is silvery - usually barium metal. Its purpose is to chemically bind stray gas molecules, keeping the vacuum intact. If you see a tube with white flashing, then the vacuum has been broken (converting the metal to barium oxide), and the tube will no longer function.

    Bozotone - any chance the tube went in that way, or were they all silver? If you've developed the color after short hours of use, I would be concerned that you've been redplating on that tube, and would need to replace it. You could plug it back in and watch the plates as you power up - being ready to turn the amp off immediately if that tube starts glowing red.

    - T
     
  7. BozoTone

    BozoTone Member

    Messages:
    557
    Joined:
    Jan 29, 2005
    Location:
    Nashville, TN.
    I didn't look at the tube before it went in. On initial "burn in", I checked every 30 mins or so for red plating in a dark room and never saw any. The checking went on for about 3 hrs. I continues to play moderately for about 2 more before I drove them hard and rechecked after that. No red plating. Again, this "set" sounds very strong...LOL, I know , sounds best before "BOOM"...I will put them back in and recheck...27mA should be well within op. specs for my amp...thanks.....
    BZT
     
  8. rockon1

    rockon1 Member

    Messages:
    11,495
    Joined:
    Aug 12, 2005
    Location:
    Stamford CT
    Makes sense.Good information! Ive often wondered why one tube in bunch of the exact same tubes will have a black getter flashing instead of silver like the rest of a bunch and it still works fine. At any rate for descriptive purposes I usually hear people refering to the getter wire as the getter itself. IE:Halo getter,d shaped getter,etc...
     
  9. Timbre Wolf

    Timbre Wolf GoldMember Supporter Gold Supporting Member

    Messages:
    8,824
    Joined:
    Oct 14, 2005
    Location:
    Berkeley, CA
    Yeah, I do that - for convenience sake.

    Seems fine to me, then, and personally, I'd run 'em. But I'd keep my eye on them now and then. I've never encountered this situation, so I'm not the expert. You may want to contact your dealer, to get a more learned opinion.

    - T
     
  10. BozoTone

    BozoTone Member

    Messages:
    557
    Joined:
    Jan 29, 2005
    Location:
    Nashville, TN.
    Ok...I have had the amp on for almost 5 hrs. with no probs. When I first turned the amp on I left it in standby for about 5 mins., then standby off and let "idle" for 15 mins watching the plates. They look great. I have played it on and off, quiet and driven and all is well...thanks.....
    BZT
     
  11. Timbre Wolf

    Timbre Wolf GoldMember Supporter Gold Supporting Member

    Messages:
    8,824
    Joined:
    Oct 14, 2005
    Location:
    Berkeley, CA
    Sounds good. Try to forget the tubes and enjoy yourself :dude

    - T
     

Share This Page