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    PSU caps question

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    popesco

    Posts : 1
    Join date : 2017-02-24

    PSU caps question

    Post by popesco on 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.
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    Bob Latino
    Admin

    Posts : 2543
    Join date : 2008-11-26
    Location : Massachusetts

    Re: PSU caps question

    Post by Bob Latino on 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

      Current date/time is Sun Aug 20, 2017 1:28 pm