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The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Tubes4hifi VTA tube amp and preamp kits and all Dynakitparts.com products


2 posters

    VTA Board Question

    mantha3
    mantha3
    mantha3


    Posts : 303
    Join date : 2010-11-10
    • Post n°1

    VTA Board Question Empty VTA Board Question

    Post by mantha3 Fri May 06, 2011 9:59 am

    Question I have in regards to the VTA board.

    How many MM wide (or Inch) are the holes on the Resistor spots on the VTA? I'm thinking of upgrading to some Caddock Higher Grade Resistors at spots R1 and R2 (Grid Resistors). These are 1% precision like what comes on the standard VTA... So on spots R1 and R2... How wide are the wider spaced lead holes?


    I'm looking to get one ot these two from Caddock:
    MK120 (10K Rated at .50 Volt) - Leads spaced 3.81 mm
    MK132 (10K Rated at .75 Volt) - Leads spaced 5.08 mm
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    mantha3
    mantha3
    mantha3


    Posts : 303
    Join date : 2010-11-10
    • Post n°2

    VTA Board Question Empty Re: VTA Board Question

    Post by mantha3 Fri May 06, 2011 10:40 am

    PS

    I also see on the ST120 schematic the R33 and R35 resistors (1K 1/2W).

    Are these not on the VTA -
    R33, R34, R35, R36 I was guessing these are on the 8 pin power tube socket pins
    R40, R41, R42, R43 I was guessing these are on the 8 pin power tube socket pins (Larger Grey ones)



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    Bob Latino
    Bob Latino
    Bob Latino
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    Posts : 3262
    Join date : 2008-11-26
    Location : Massachusetts
    • Post n°3

    VTA Board Question Empty Re: VTA Board Question

    Post by Bob Latino Fri May 06, 2011 3:39 pm

    The eyelet spacing on R1 and R2 is exactly 1/2 inch or about 12.7 mm

    Some of the resistor (and capacitor) locations on the VTA driver board have multiple eyelets. This is done to give flexibility in what types of resistors and capacitors the board may use. All the resistors on the standard gain board are 1/2 watt. The lower gain version of the board uses 1 watt and 2 watt resistors in a few locations.

    R33 - R35 are 1K 1 watt resistors found between pins 5 and 6 on each output tube.

    R40 - R43 are the 10 ohm 2 watt bias resistors that are connected from pin 8 of each output tube to chassis ground.

    Bob
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    mantha3
    mantha3
    mantha3


    Posts : 303
    Join date : 2010-11-10
    • Post n°4

    VTA Board Question Empty Re: VTA Board Question

    Post by mantha3 Sat May 07, 2011 9:03 am

    I appreciate the help Bob.

    So, I'm looking at some Caddock High Performance Film Resistors... I'm looking at the MS176 line to use in place of the 1/2 Watt. These are .75 watt. I think the higher wattage rating is not a problem... Right?

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    Bob Latino
    Bob Latino
    Bob Latino
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    Posts : 3262
    Join date : 2008-11-26
    Location : Massachusetts
    • Post n°5

    VTA Board Question Empty Re: VTA Board Question

    Post by Bob Latino Sat May 07, 2011 9:18 am

    No problem in using a 3/4 watt resistor in place of a 1/2 watt resistor.

    Bob
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    • Post n°6

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