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    Voltage on the VTA board



    Posts : 18
    Join date : 2012-07-11

    Voltage on the VTA board

    Post by ixe13 on Mon Jul 16, 2012 5:20 pm

    Hi Guys,

    I see a lot of ST-70 amps photos around on the internet and a lot of them doesn't have a cage.

    Got me wondering: How much voltage is there on the board? affraid Is it dangerous to leave it open like this?


    Bob Latino

    Posts : 2454
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Voltage on the VTA board

    Post by Bob Latino on Mon Jul 16, 2012 6:17 pm

    Hi Yves,

    You have 350+ volts DC on certain components on almost any ST-70 driver board. If you don't touch the board while the amp is running - then no problem ... If, however, you have young children or pets that *could* accidentally touch some component on the driver board, then just get yourself a tube cage. Sometimes you can find a used tube cage on Ebay. You can also buy an excellent replica Dynaco/Dynakit tube cage from

    Personally I like the look of the amp without a tube cage. I don't have any young children here but Chris and I do have a cat. For the past 7 years we have had the cat, it has never expressed any interest in the amp while it was on. You can also place the amp on the top of an audio component rack where kids or pets won't have any access.



    Posts : 18
    Join date : 2012-07-11

    Re: Voltage on the VTA board

    Post by ixe13 on Mon Jul 16, 2012 7:54 pm

    Hi Bob,

    I agree, the look without the cage is much nicer.

    What I did on mine, I bought Roy's plexiglass plate that goes on top of the board. The prototype one that you advertised a while ago.

    I wasn't sure about the voltage at that time, but found the idea of a plexiglass plate pretty cool... Was thinking to
    install a few colored diode of some sort around the board inside the amp. Cause you see, when I installed the plate, the board
    ended up a bit lower than normal, so there's a small space between the board's edge and the chassis.

    Thought that with some light coming from inside the amp and reflecting on the plexiglass could make a nice visual effect.
    You know, like these old B-15 Ampeg Bass Amp.
    But never got around doing it... If anybody wanna use the idea, just go ahead and post some photos...

    Does Roy still have these for sale?

    I might restore an old ST-70, and was thinking to use one of these plexiglass plate.

    Thanx for the info by the way!



    Posts : 1308
    Join date : 2008-11-30

    Re: Voltage on the VTA board

    Post by tubes4hifi on Fri Jul 20, 2012 5:11 pm

    plexi covers still available, but I only sell a couple of them every year, so special order only


    Posts : 51
    Join date : 2011-12-20

    Re: Voltage on the VTA board

    Post by bktheking on Wed Jul 25, 2012 10:48 am

    I run mine with the plexiglass plate over the board.

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