first time changing tube,preemptive advise sought

Discussion in 'Ampage Area' started by mandobandit, Jun 27, 2019.

  1. mandobandit

    mandobandit Gretschie

    129
    Apr 1, 2019
    Ohio
    You may have seen earlier in the week where I posted regarding dead Blackstar 20 watt Studio mkII
    I contacted Sweetwater as it is new since February, as to what to do to remedy situation .
    They are so pleasant to work with.
    Kevin my sales guy put me in touch with tech support, he had me try running my guitar into the loop return to attempt to determine if pre-amp or power output could be determined, they have sent a full complement of new glass to make the swap.
    I have not done this before, but from what I've read on the web is that 20 watts and under do not require biasing as they are cathode based, am I understanding that correctly?
    I am a fairly tech savvy guy and work as a structural designer, so I'm comfortable with making the swap( I've re fretted several guitars and made invasive mods etc.), just want the benefit of the group, as I know many here do this on a regular basis.
    Hoping to get time this evening, as the tubes have arrived at home.
    thank you all
    Fred
     
    MKunie likes this.
  2. Uncle Daddy

    Uncle Daddy Friend of Fred

    Jan 19, 2012
    Maldon UK
    Wait till the amp is cold. Start from V1, the one on the furthest right. You may have to remove a metal cover, which normally has bayonet fittings. The tube pins are often tight in the socket, so go carefully. Gently pull the glass tube down; you might have to rock it a bit. Look at the pins. You will see an indexing slot on the centre spigot that needs lining up with a slot in the tube socket. Rotate the tube pins against the base until the slot and spigot engage, then gently push the tube home. Again, it may need a wriggle.

    It's really no more difficult than changing a light bulb.

    Briefly turn the amp on, and see if the problem has resolved. If it has, you know which tube was to blame. If not, go on to V2 and do the same, once it's cooled off. Eventually you may have changed all of them, and still have a problem, in which case the tubes were not to blame and to need more help.

    You are right about cathode-biased power tubes. Plug and play.
     
  3. Uncle Daddy

    Uncle Daddy Friend of Fred

    Jan 19, 2012
    Maldon UK
    If the whole amp is dead, you may need a fuse swap too. If a new fuse blows, you have a bigger problem. You can always check the old one with a meter if you don't have a spare.
     
  4. tartanphantom

    tartanphantom Country Gent

    Age:
    56
    Jul 30, 2008
    Murfreesboro, TN
    Be sure to handle the tubes with gloves, paper towels, or a shop cloth... Just something to keep your fingerprints off if the glass bottles. The oil from your fingers can cause a hot spot on the glass, which can cause a weak area on the bottle over time.

    Personally, I use disposable nitrile gloves... But even rubber dishwashing gloves will do. Sometimes it's hard to get a good grip using a cloth or paper towel.
     
    wabash slim likes this.
  5. wabash slim

    wabash slim Friend of Fred

    Age:
    69
    Feb 10, 2010
    lafayette in
    The small preamp tubes will have a gap between two of the pins so you index them that way. Gloves or paper towels are important---I had to do that with theatrical stage and projection lamps all the time. The lamps would balloon up and burst if it wasn't done. At over a hundred dollars for most, and up to the thousands for some projection lamps, it was really necessary.

    Check your amps manual for bias needs.
     
  6. mandobandit

    mandobandit Gretschie

    129
    Apr 1, 2019
    Ohio
    You guys are awesome so generous with your knowledge and time.
    I truly appreciate all.
    You have confirmed all that I suspected and had planned for though I meant to look at the type and amps so I could pick a couple up.
    There are several auto parts retailers near home do you suppose I could pick up what I will need there and would anyone know what fuses might be required
    Again thank you all
    Fred
     
  7. MotorCentaur

    MotorCentaur Gretschie

    267
    May 11, 2016
    Seattle
    Audio valves/tubes are NOT projector/halogen bulbs, they don't get anywhere near as hot. If touching them with bare hands was critical, there would be warnings on all of their boxes. You wouldn't want to get motor oil or chicken grease on them, but oils just from handling them with clean hands is insignificant to their lifespan.

    I would be more concerned that the trouble may be something other than the tube itself. Often enough tubes down are just the symptoms of other ailments like blown resistors that feed the tubes voltages. Just don't go opening up the chassis and poking around unless you know what you are doing. The capacitors store lethal voltages that can kill you if they aren't discharged properly.
     
    Robbie likes this.
  8. mandobandit

    mandobandit Gretschie

    129
    Apr 1, 2019
    Ohio
    I appreciate that cautionary.
    I have read of same, I’m only attempting changing of valves and fuses if needed.
    Beyond that it is under warranty , Sweetwater tech department has included guidance with the replacement tubes, and I have my Katana 50 for home and my HT 40 mkII at practice space.
    Not going near stupid
     
  9. Uncle Daddy

    Uncle Daddy Friend of Fred

    Jan 19, 2012
    Maldon UK
    I read your other post and saw that the amp powers up, in which case the fuse won't be the issue.

    I once spent ages troubleshooting a volume problem. Guess how silly I felt when I realised the master volume on the guitar was all the way down!

    Almost as silly as when I spent an hour looking for a bunch of keys that were in my hand.
     
    section2 and radd like this.
  10. mandobandit

    mandobandit Gretschie

    129
    Apr 1, 2019
    Ohio
    Amp powers up no sound
     
  11. speedicut

    speedicut Friend of Fred

    Jun 5, 2012
    Alabama
    When I was a projectionist in a movie theater in the 80's we had Xenon bulbs and had to use gloves and a face shield when changing them out.
    I was up there once and heard a loud BOOM! and thought someone had fired a gun.
    It was a bulb exploding and it embedded glass in the metal projection cover!
     
    Merc likes this.
  12. wabash slim

    wabash slim Friend of Fred

    Age:
    69
    Feb 10, 2010
    lafayette in
    I had one go when I was standing next to a PJ. They were housed in a heavy plastic container that was "explosion proof". Never wanted to find out if that was true. The capacitors in a Xenon power supply were like a gunshot when the blew as well. We converted all of our carbon arc lamps over to Xenon---some up to 4KW units. 14 follow spots in our big theater alone, as well as 16mm, 35mm film PJs, and 12 slide PJs, and 4 FX PJs. Carrying the new power supplies up the stairways was even more fun.
     
    Merc likes this.
  13. pmac11

    pmac11 Country Gent

    Age:
    55
    Mar 4, 2018
    Toronto, Ontario
    If your amp powers up, are any of the tubes NOT glowing?

    Sent from my SM-T560NU using Tapatalk
     
  14. radd

    radd Country Gent

    Dec 27, 2017
    Santa cruz
    If you can’t find your glasses I bet I know where they are....on top of your head. Just thought I would help.

    Not that I have done any of those things, heavens no...Me?
     
  15. mandobandit

    mandobandit Gretschie

    129
    Apr 1, 2019
    Ohio
    I’m just getting ready to check that gotta switch laundry first
    Once I contacted Sweetwater tube replacements were in the mail before I could ask a second question lol
    I must spend too much money with them ;)
     
    pmac11 likes this.
  16. mandobandit

    mandobandit Gretschie

    129
    Apr 1, 2019
    Ohio
    well I keep all original packaging, which is good because I will be contacting Sweetwater to see what's next.
    You guessed it no sound, tubes glow, I did swap for the Mesa tubes they sent but to no avail.
    I put the Ruby tubes back in, I did learn some things taking it apart.
    I'm confident Sweetwater will do right by me, I received it end of January so well within warranty.
     
  17. pmac11

    pmac11 Country Gent

    Age:
    55
    Mar 4, 2018
    Toronto, Ontario
    Is the speaker connected? Sometimes one of the leads comes loose.
     
    new6659 likes this.
  18. Henry

    Henry Gretschified

    Apr 9, 2014
    Petaluma
    Yea, return it right away. You should not have to fix it or be without the amp for an extended period.
     
    pmac11 likes this.
  19. mandobandit

    mandobandit Gretschie

    129
    Apr 1, 2019
    Ohio
    Yes checked
     
  20. Funky54

    Funky54 Gretschie

    238
    Aug 12, 2010
    Florida
    In 30 years nobody has ever told me this. I have probably installed hundreds and hundreds of tube, not to mention tube rolling in preamps for my stereo gear. I have always washed my hands with soap and water. I never understood why some would actually send gloves with their products. I wish I would have known this years ago.
     
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.


  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice