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    ST120 completed

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    mikescaggs

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    ST120 completed

    Post by mikescaggs on Sun Jan 06, 2019 9:41 am

    Hello Forum,

    Mike here and this is my first post.  I just finished my VTA ST120 and I'm pretty happy with her.  It didn't come without a few issues which of course is a good way to get to know your amp better.  When I finished it all was good but after a few days the right side went bad.  I had a very low and distorted volume and something was definitely not right.  First thing I did was start checking voltages and found the plate on the R driver tube was a little above 400vDC.  Through a ton of troubleshoot I determined the LM334 was bad indeed it was.  She's all back together now and sounding amazing.  Running a quad set of KT120s, BugleBoy 5AR4, and some nice Amprex 12AU7s.

    Pics here
    http://www.p2pamps.com/st120


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    cci1492

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    Re: ST120 completed

    Post by cci1492 on Sun Jan 06, 2019 11:02 am

    Welcome Mike, that is an amazing job you did. That model is probably the toughest one to build with a clean look because of the somewhat limited room, but you pulled it off. Now enjoy the beautiful music it no doubt makes. Which speakers are you using with it?
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    mikescaggs

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    Re: ST120 completed

    Post by mikescaggs on Sun Jan 06, 2019 11:05 am

    cci1492 wrote:Welcome Mike, that is an amazing job you did. That model is probably the toughest one to build with a clean look because of the somewhat limited room, but you pulled it off. Now enjoy the beautiful music it no doubt makes. Which speakers are you using with it?

    Thanks CCI, I appreciate that. It was a lot of fun to build. I normally do guitar amps and 100s of them so this was a nice break-away for me. I did do my heaters like I do on amps, just a thing with me LOL...
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    cci1492

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    Re: ST120 completed

    Post by cci1492 on Sun Jan 06, 2019 11:29 am

    Mike, did you consider the "yellow sheet mode"? It would help protect that nice rectifier tube.
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    mikescaggs

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    Re: ST120 completed

    Post by mikescaggs on Sun Jan 06, 2019 11:33 am

    cci1492 wrote:Mike, did you consider the "yellow sheet mode"? It would help protect that nice rectifier tube.

    "yellow sheet mode"?



    Last edited by mikescaggs on Sun Jan 06, 2019 11:36 am; edited 1 time in total
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    cci1492

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    Re: ST120 completed

    Post by cci1492 on Sun Jan 06, 2019 11:34 am

    http://dynacotubeaudio.forumotion.com/t1006-tube-rectifier-diode-mod

    If you don't have the diode PM me and I'll drop a few in the mail for you.
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    mikescaggs

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    Re: ST120 completed

    Post by mikescaggs on Sun Jan 06, 2019 11:37 am

    cci1492 wrote:http://dynacotubeaudio.forumotion.com/t1006-tube-rectifier-diode-mod

    If you don't have the diode PM me and I'll drop a few in the mail for you.

    Ok, yeah I did that after the pics... I normally do that on all tube rectifier guitar amps too. Good call Smile
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    Bob Latino
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    Re: ST120 completed

    Post by Bob Latino on Sun Jan 06, 2019 12:05 pm

    Mike,

    Very nice work on the build of your VTA ST-120 amp ... I especially like the transformer bells painted in "Ford Blue" and then the black on the transformer plates. This is a really sharp combination. The VTA clear cover over the driver board was done so well, I almost did not see the driver board cover at first. Thanks for the link to the photos of your build ..

    Bob
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    erhard-audio

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    Re: ST120 completed

    Post by erhard-audio on Sun Jan 06, 2019 12:12 pm

    yes, that is a SUPER neat and clean job, excellent work!
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    cci1492

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    Re: ST120 completed

    Post by cci1492 on Sun Jan 06, 2019 4:39 pm

    Yours is very nice, but this one beats it:



    The fuse terminator!
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    pedrocols

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    Re: ST120 completed

    Post by pedrocols on Sun Jan 06, 2019 9:48 pm

    I like it!
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    mikescaggs

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    Re: ST120 completed

    Post by mikescaggs on Sun Jan 06, 2019 10:21 pm

    cci1492 wrote:Yours is very nice, but this one beats it:



    The fuse terminator!

    LMBO!!!

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    cci1492

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    Re: ST120 completed

    Post by cci1492 on Sun Jan 06, 2019 10:38 pm

    mikescaggs wrote:
    cci1492 wrote:Yours is very nice, but this one beats it:



    The fuse terminator!

    LMBO!!!


    Bob knows the back story to that build, he posted that picture. I think it was blowing fuses and the guy called Bob for some help to figure it out.
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    mikescaggs

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    Re: ST120 completed

    Post by mikescaggs on Sun Jan 06, 2019 10:51 pm

    cci1492 wrote:
    mikescaggs wrote:
    cci1492 wrote:Yours is very nice, but this one beats it:



    The fuse terminator!

    LMBO!!!


    Bob knows the back story to that build, he posted that picture. I think it was blowing fuses and the guy called Bob for some help to figure it out.

    Yes that's true, turned out I had an opened up 330K resistor in the SMC.  Odd but true...  Without a schematic I knew Bob would know this circuit much better than I since this was my first Dynaco build. Definitely hit a few bumps but worked em out.
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    mikescaggs

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    Re: ST120 completed

    Post by mikescaggs on Sun Jan 06, 2019 11:18 pm

    cci1492 wrote:http://dynacotubeaudio.forumotion.com/t1006-tube-rectifier-diode-mod

    If you don't have the diode PM me and I'll drop a few in the mail for you.

    BTW, Thanks for the link... I do have hundred of those diodes in the parts cabinet but I really do appreciate it
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    bbqjoe

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    Re: ST120 completed

    Post by bbqjoe on Sun Jan 06, 2019 11:30 pm

    Oh man!
    That fuse fryer is a piece of work there! It's a beaut!!!

    DarthBubba

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    Re: ST120 completed

    Post by DarthBubba on Tue Jan 08, 2019 2:11 am

    cci1492 wrote:Yours is very nice, but this one beats it:


    When I looked at this the lead-in from Guns-n-Roses "Welcome to the Jungle" started playing in my head.  affraid
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    bbqjoe

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    Re: ST120 completed

    Post by bbqjoe on Tue Jan 08, 2019 2:55 am

    DarthBubba wrote:

    When I looked at this the lead-in from Guns-n-Roses Welcome to the Jungle started playing in my head.  affraid

    I'm surprised there aren't a few band-aids wrapped around some of that!

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