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    Bad Power Tube?

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    bigmm79

    Posts : 23
    Join date : 2010-09-15

    Bad Power Tube?

    Post by bigmm79 on Wed Nov 10, 2010 9:09 pm

    Checked the bias on my tubes tonight and one was unusually high - .70. These are Gold Lion KT66s and I keep them biased at .45. Turn bias pot all the way down and it won't go any lower than .65. I know its this power tube because the problem moves with it. I guess the tube has gone bad somehow, despite probably less than 100 hours of use. What does this symptom say about the tube? What's likely wrong with it?
    Big disappointment - expensive tube.

    kevco

    Posts : 70
    Join date : 2009-07-16
    Location : Aldan, PA, USA

    Re: Bad Power Tube?

    Post by kevco on Thu Nov 11, 2010 1:41 am

    It's running away...Often buying power tubes that have been burned in by the seller and then matched again will lower the incidence of this occurring, but it will still happen to the best of us. An XF2 Mullard bought in 1961 for a dollar could do this and so can a reissue KT66 bought for 40 dollars in 2010. Any seller worth a web page designer should warranty the tube for 30 days. Send it back, it IS an expensive tube!

    Bob Latino
    Admin

    Posts : 2374
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Bad Power Tube?

    Post by Bob Latino on Fri Nov 12, 2010 5:01 pm

    A good point here by Kevco ... Always keep the dated receipt for any tube purchase. Every now and then, for no good reason, even a NEW tube does go bad ? All GOOD tube vendors will give a 90 warranty on new tube purchases. Just Email the vendor and explain the situation to him. You will always have to send the tube back to the vendor at your expense. The vendor will then send you a replacement at his expense.

    Bob

    bigmm79

    Posts : 23
    Join date : 2010-09-15

    Re: Bad Power Tube?

    Post by bigmm79 on Fri Nov 12, 2010 6:01 pm

    Fortunately I did buy this from a good vendor that does have a 90 day warranty and has sent me a replacement. In fact, they shipped the replacement right out without waiting for the bad tube to arrive back from me. It is indeed worth a few extra bucks to buy from a good dealer that is communicative and offers a solid warranty.

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