The Dynaco Tube Audio Forum

Would you like to react to this message? Create an account in a few clicks or log in to continue.
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

    PSU caps question

    popesco
    avatar
    popesco


    Posts : 1
    Join date : 2017-02-24
    • Post n°1

    PSU caps question Empty PSU caps question

    Post by popesco Fri Feb 24, 2017 9:59 am

    Hello everybody Smile

    I need an advice from you guys. I have on my way, an old Dynaco st-70. From the start i want to change a few things.

    I will be moving the parts to a new case. I'm going to replace the driver with a VTA board. Change the power transformer so i can later use kt88 tubes.

    Also i want to remove the quad cap and build a small psu board. This is where i need your help.

    I already have 2x82uF 450v, 2x270uF 450v. So, using 40uf - choke - 135uf would be enough to drive the kt88? Should i add more? The VTA board already has 2x47uF and 2x100uF.

    Thanks.
    • Back to top
    Bob Latino
    Bob Latino
    Bob Latino
    Admin


    Posts : 3276
    Join date : 2008-11-26
    Location : Massachusetts
    • Post n°2

    PSU caps question Empty Re: PSU caps question

    Post by Bob Latino Fri Feb 24, 2017 1:11 pm

    popesco wrote:Hello everybody Smile

    I need an advice from you guys. I have on my way, an old Dynaco st-70. From the start i want to change a few things.

    I will be moving the parts to a new case. I'm going to replace the driver with a VTA board. Change the power transformer so i can later use kt88 tubes.

    Also i want to remove the quad cap and build a small psu board. This is where i need your help.

    I already have 2x82uF 450v, 2x270uF 450v. So, using 40uf - choke - 135uf would be enough to drive the kt88? Should i add more? The VTA board already has 2x47uF and 2x100uF.

    Thanks.

    I don't believe that you need anymore capacitance than what you have listed. Just remember that the last cap in the chain after your 2 X 270 uF in series has to have a "drop-down" resistor of about 2.2K before sending the B+ to the VTA driver board.

    Bob
    • Back to top
      Current date/time is Fri Nov 22, 2024 12:57 pm