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    all tubes lit no sound

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    scottlowe

    Posts : 38
    Join date : 2014-04-05

    all tubes lit no sound

    Post by scottlowe on Tue Apr 15, 2014 4:06 pm

    My st 120 has all tubes lit but no sound . I am taking it in wednesday and am wanting to know if it could be something very expensive or could it also be something not too costly ?

    MontanaWay

    Posts : 781
    Join date : 2014-02-06
    Age : 58
    Location : Brookings, Oregon

    Re: all tubes lit no sound

    Post by MontanaWay on Tue Apr 15, 2014 4:42 pm

    I would check your B+, see if there is a problem with that.
    The filament supply is separate from your B+, so the tubes would be lit even if the B+ is not present.
    I am pretty sure I'm right with this, perhaps other members can chime in here as well.

    tubes4hifi
    Admin

    Posts : 1282
    Join date : 2008-11-30

    Re: all tubes lit no sound

    Post by tubes4hifi on Tue Apr 15, 2014 5:23 pm

    maybe just one missing wire somewhere!

    MontanaWay

    Posts : 781
    Join date : 2014-02-06
    Age : 58
    Location : Brookings, Oregon

    Re: all tubes lit no sound

    Post by MontanaWay on Tue Apr 15, 2014 5:26 pm

    is this a new build ST120?, did you build it if it is?
    As tubes4hifi said, check the wiring, but like my first reply, if you have a meter, check your B+

    sKiZo

    Posts : 1308
    Join date : 2013-04-01
    Location : Michigan USA

    Re: all tubes lit no sound

    Post by sKiZo on Tue Apr 15, 2014 5:49 pm

    Got some spare driver tubes you can plug in? No signal, no sound ... try swapping the center and one of the side tubes and see if you can get one channel to work. That happens, replace the center.

    You could also try re-tensioning the sockets. There's three tabs for each pin that can loosen up and go intermittent. Those can be pushed in a bit - carefully - a jeweler's screwdriver works nice for that.

    As always, power down when playing with tubes, and let the amp "rest" a couple minutes before powering it back up so the caps can discharge properly. Fast cycling the power can cause all sorts of grief.

    Bob Latino
    Admin

    Posts : 2411
    Join date : 2008-11-26
    Location : Massachusetts

    Re: all tubes lit no sound

    Post by Bob Latino on Tue Apr 15, 2014 6:25 pm

    The most common cause of "all tubes light up but no sound" is a BAD rectifier tube. Even if the rectifier tube lights up also, that does not mean that is still good. An "all tubes light up with no sound and NO BIAS voltage" is almost always a bad rectifier tube.

    Try a new rectifier tube before you send the amp in anywhere to be repaired ..

    Bob

    deepee99

    Posts : 1332
    Join date : 2012-05-23
    Location : Wallace, Idaho

    Re: all tubes lit no sound

    Post by deepee99 on Sun Apr 20, 2014 7:26 pm

    Just from personal experience, check/re-solder your bias adjustment pots on the driver board. I had a lame solder connection on one of the three pins and no sound came out. (except some expletives from me).

    j beede

    Posts : 328
    Join date : 2011-02-07
    Location : California

    Re: all tubes lit no sound

    Post by j beede on Sun Apr 20, 2014 8:41 pm

    Get yourself a spare 5AR4. If you have a Guitar Center nearby you should be able to pick up a Sovtek 5AR4/GZ34 for less than $15 there.

    scottlowe

    Posts : 38
    Join date : 2014-04-05

    Re: all tubes lit no sound

    Post by scottlowe on Sun May 04, 2014 9:52 pm

    Hi It turned out to be a problem with the soft start. I have had this amp for 16 months and only used it for about a week and wow it sounds great my friend said it didn't sound like a tube amp so much as it sounded like a band playing right over there .! Nice Amp Bob

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