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    hey HEY! It's ALIVE!!

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    Dingojazz

    Posts : 39
    Join date : 2010-09-03

    hey HEY! It's ALIVE!!

    Post by Dingojazz on Tue Mar 11, 2014 2:31 pm

    Post below described issues with blowing fuses on Mk III build...
    Lots of help received here from kind souls NJ Sal, Stew, Stromberg-Kevin, et. al..

    Long story short, found the short (doh!), and was able to power up the Mk. III for the first time today.
    It's got a ways to go for break in, but it biases, and is now pumping out tunes in glorious mono-phonic sound.

    I can't thank enough all those who lent their time/expertise.

    Great board.

    K.

    Sal

    Posts : 223
    Join date : 2009-02-05
    Location : Central New Jersey Dynaco-ST70.com

    Re: hey HEY! It's ALIVE!!

    Post by Sal on Tue Mar 11, 2014 5:16 pm

    Hi Kevin,
    That is great news. I read the PM you sent me, It's hard to believe an ungrounded RCA jack caused your headache. I don't have a schematic for the VTA board you used to see if this is possible. Maybe Roy can chime in here and let us know. But if that is what fixed it.... Can you do one test, set your meter to read 600v DC or greater and measure the voltage from the ground of your RCA jack to chassis ground. Let us know what you read.

    Sal

    Sal

    Posts : 223
    Join date : 2009-02-05
    Location : Central New Jersey Dynaco-ST70.com

    Re: hey HEY! It's ALIVE!!

    Post by Sal on Tue Mar 11, 2014 5:31 pm

    I am looking at your MK3 picture again, looks like the RCA jack ground wire connected to the printed circuit board that is already grounded to the chassis by the mounting screw unless the ground plane on the board is not under the screw.... this does not make sense to me...

    Sal

    Dingojazz

    Posts : 39
    Join date : 2010-09-03

    Input Ground

    Post by Dingojazz on Wed Mar 12, 2014 7:25 pm

    Yeah, I dunno, it didn't make sense to me either, but there was a short there somewhere that was cured by
    reinstalling the stock (crappy) input.  I'll get an upgraded insulated version at some point.

    The ground setup on Roy's board is per his layout schematic.  

    I'll try the test you identify and see what's what..

    Thanks again,

    Kevin


    Last edited by Dingojazz on Sat Mar 15, 2014 12:44 am; edited 1 time in total

    Sal

    Posts : 223
    Join date : 2009-02-05
    Location : Central New Jersey Dynaco-ST70.com

    Re: hey HEY! It's ALIVE!!

    Post by Sal on Wed Mar 12, 2014 8:05 pm

    If the ground of the RCA jack is grounded to the chassis, no need to check the voltage as you will measure zero..

    Sal

    Dingojazz

    Posts : 39
    Join date : 2010-09-03

    Re: hey HEY! It's ALIVE!!

    Post by Dingojazz on Sat Mar 15, 2014 12:45 am

    Right-o.

    K.

    PS: Two Mk IIIs up and running now, still breaking in but sounding great!

    sKiZo

    Posts : 1287
    Join date : 2013-04-01
    Location : Michigan USA

    Re: hey HEY! It's ALIVE!!

    Post by sKiZo on Sat Mar 15, 2014 8:01 pm

    Great to hear ...

    I'd keep a close eye on the bias for a bit to make sure you didn't stress any tubes while working it out ... A week or two out without any problems, and a monthly check should oughta do ya ...


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