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    Help Need with Mark VI Bias Issue



    Posts : 1
    Join date : 2011-02-14

    Help Need with Mark VI Bias Issue

    Post by Liv2Ski on Mon Feb 14, 2011 9:53 pm

    Hello all:

    I am a new forum member and unfortunately, not very technically oriented. I have a pair of Mark VI amps that I am attempting to get running for the first time in about 20 years. I have purchased NOS matched quad 8417's. The amps power up and drive my speakers ok and all the tubes appear to be glowing normally and equally. However, I cannot set the bias for zero on either amp (I know it worked 20 years ago) - even after warming up for a few hours, the meter will not show higher than about -7db. The pots have full travel and do affect the meter readings, but not higher than the afore-mentioned -7db. The manual says that if I cannot set the bias to zero, I should not run the amps until I figure out what is going on, but doesn't direct me how to troubleshoot or fix it. As you can imagine - I am bummed! I'm hopeful that someone here may be able to guide me towards a solution. Any and all advice, insights, or just plain needling will be gratefully accepted.

    Thanks all,


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