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    VTA initial start up problem

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    grizzinca

    Posts : 40
    Join date : 2012-01-01

    VTA initial start up problem

    Post by grizzinca on Fri Nov 30, 2012 10:09 pm

    Need some help. Built your vta board, installed in in an st 70 using the instructions and pics as instructed. When I plug in and power up, the 2 outside 12AT7's get warm but don't light up. The center 12AT7 wont even get warm. I checked the voltage across the 2 wires that connect to the board from V3 and V6 and get 6.1 VAC. Where do look next?

    danskman

    Posts : 17
    Join date : 2012-01-14
    Age : 57
    Location : Bière, Switzerland

    Re: VTA initial start up problem

    Post by danskman on Sat Dec 01, 2012 3:53 am

    Welcome aboard!
    I wouldn't worry about not seeing the filament shining in the two outer 12AT7, some tubes show it, some don't, depending of their structure; if they get warm, the filament should do its work. The center tube should get warm, too. Try to cross it with another 12AT7 and check if it gets warm. If not, triple-check the diagram and the filament wiring on the VTA board, you should find the problem easily.
    Good luck,
    Daniel

    grizzinca

    Posts : 40
    Join date : 2012-01-01

    Re: VTA initial start up problem

    Post by grizzinca on Sat Dec 01, 2012 8:47 am

    Thanks Daniel. I'll start there. Hope to be up and running soon

    Bob Latino
    Admin

    Posts : 2378
    Join date : 2008-11-26
    Location : Massachusetts

    Re: VTA initial start up problem

    Post by Bob Latino on Sat Dec 01, 2012 9:32 am

    grizzinca wrote:Need some help. Built your vta board, installed in in an st 70 using the instructions and pics as instructed. When I plug in and power up, the 2 outside 12AT7's get warm but don't light up. The center 12AT7 wont even get warm. I checked the voltage across the 2 wires that connect to the board from V3 and V6 and get 6.1 VAC. Where do look next?

    Hi,

    If you have one of the newer CCS driver boards, you have to install TWO FILAMENT JUMPER wires on the bottom of the driver board from the right side 12AU7 tube socket to the center 12AU7 socket to provide 6.3VAC for the center tube's filament. I am not sure that this is the reason why your center 12AU7 does not light up but check that you did install these two jumper wires. Without these two wires installed, the center 12AU7 will not light up.

    Bob

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