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    Question about VTA mod board

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    j4570

    Posts : 141
    Join date : 2010-08-30

    Question about VTA mod board

    Post by j4570 on Mon Sep 06, 2010 4:00 pm

    So I've decided when I rebuild the ST70 I picked up, I'll use the VTA driver board. I considered buying he "Rebuild" kit for the ST70 from tubes4hifi, but instead I think I'm going to get the VTA board there, and the cap and speaker terminals from dynakitparts. Anyway, here is a pic of the VTA board beside the original:

    http://www.tubes4hifi.com/bob2.htm

    Does the VTA board eliminate the need to put the diode in to replace the selenium rectifier (ie, it's now on board of the VTA)? I can't find the diode in there anywhere on the bottom of that amp (oddly, the diode and terminal strip are shown further down on the page, adding to my confusion).

    I found the instructions and it looks like the diode and strip is gone with VTA mod.

    Also, when buying the upgraded PIO caps, do the others get upgraded to Orange Drops?

    Does the 3 lug terminal strip with the yellow caps come with the VTA kit as well?

    The instructions say to reuse the strip and caps. I think I'd rather have a new strip and caps.

    I looked on the site for instructions on the VTA board but couldn't find them. FOUND THEM. Duh, look at the bottom of the page. I was looking with the original manuals.

    My intent is to "gut" the amp and basically start over building a ST70. New Sockets, switch, cord, screws, etc. Is there a set of instructions to build the ST70 with VTA board (and posssibly triode/pentode switch) all at once, or will I need to mix/match instructions? Looks like it's pretty much covered in the instructions I found.

    Thanks,

    Jason


    Last edited by j4570 on Mon Sep 06, 2010 4:58 pm; edited 1 time in total

    j4570

    Posts : 141
    Join date : 2010-08-30

    Re: Question about VTA mod board

    Post by j4570 on Mon Sep 06, 2010 4:55 pm

    OK, I found instructions on the site. Don't know how I missed them. Still a few questions.

    Bob Latino
    Admin

    Posts : 2411
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Question about VTA mod board

    Post by Bob Latino on Mon Sep 06, 2010 5:12 pm

    Hi Jason,

    Re: > "Does the VTA board eliminate the need to put the diode in to replace the selenium rectifier (ie, it's now on board of the VTA)? I can't find the diode in there anywhere on the bottom of that amp (oddly, the diode and terminal strip are shown further down on the page, adding to my confusion)."

    Yes - the VTA board has the bias diode on the board - there is no need for the photo of the diode and terminal strip on that web page - It was put on that page in error. Thanks for pointing this out. The photo will be removed ASAP.

    Re:"Also, when buying the upgraded PIO caps, do the others get upgraded to Orange Drops?"

    No - The .22 uF Russian PIO caps are only for the 4 main coupling caps. The four .10 uF @ 400 volt orange drop caps are not replaced. I have changed out those 4 orange drop caps to the PIO caps it makes no difference in the sound. I have tried it before ..

    Re:"Does the 3 lug terminal strip with the yellow caps come with the VTA kit as well?"

    No - You reuse the original dual .022 uF @ 100 volt caps that are now on lugs 5, 6 and 7 of the 7 lug terminal strip.

    Re: > "I looked on the site for instructions on the VTA board but couldn't find them."

    Email me at Bob01605@aol.com and I can send you a copy ..

    Re: > "My intent is to "gut" the amp and basically start over building a ST70. New Sockets, switch, cord, screws, etc. Is there a set of instructions to build the ST70 with VTA board (and posssibly triode/pentode switch) all at once, or will I need to mix/match instructions?"

    Right at the bottom of the rebuild web page are TWO links to rebuild manuals. One is a complete ST-70 rebuild with the VTA driver board and NO triode/pentode switches and the other link is a complete rebuild WITH the triode/pentode switches.

    Bob

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