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    clone with one side not right

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    natoe

    Posts : 34
    Join date : 2010-03-06
    Location : Pittsburgh, PA

    clone with one side not right

    Post by natoe on Mon Apr 26, 2010 6:01 pm

    Bob I just finished up the clone with that pesky board and the one channel is really low in volume I checked all joints swap tubes and double checked everything else.any ideas would help to point me in the right direction.

    thanks pete

    Sal

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

    Re: clone with one side not right

    Post by Sal on Mon Apr 26, 2010 6:30 pm

    Make sure you didn't make a mistake with resistor values like a 47 ohm resistor instead of a 47K ohm resistor plus make sure you connected the audio transformer correctly.

    If you can take a photo or 2 that might help us diagnose your problem.

    Sal

    Bob Latino
    Admin

    Posts : 2376
    Join date : 2008-11-26
    Location : Massachusetts

    Re: clone with one side not right

    Post by Bob Latino on Mon Apr 26, 2010 6:40 pm

    Pete,

    The problem is not the cap board unless the RED transformer wire connected to the cap board has a bad solder connection.

    Sal's advice is very good. With the AMP OFF measure the resistance of every resistor on the driver board with it's "mate" on the other side of the driver board. See if you can find a variation from one of the left channel's resistors to it's "mate" on the right side of the board.

    Another thing you can try is the "shotgun approach" - you resolder every connection on the weak channel. You may have a cold solder connection and not know it ?

    Bob

    natoe

    Posts : 34
    Join date : 2010-03-06
    Location : Pittsburgh, PA

    Re: clone with one side not right

    Post by natoe on Mon Apr 26, 2010 9:18 pm

    here are a few pics. did what was said all resistors look ok i thought i might have the inputs wired wrong too.

    thanks pete

    I don't know how to post the pics. thanks guys


    Last edited by natoe on Mon Apr 26, 2010 9:34 pm; edited 1 time in total (Reason for editing : no pics)

    Sal

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

    Re: clone with one side not right

    Post by Sal on Tue Apr 27, 2010 10:13 am

    Pete,
    I sent you a pm with my email address, if you email me your photos, I will post them here.

    Sal

    Sal

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

    Re: clone with one side not right

    Post by Sal on Tue Apr 27, 2010 9:42 pm

    Attached are Pete's photos of his ST-70. IF you right click and choose view image you will see the full size of the photo.

    Sal






    Luddite

    Posts : 235
    Join date : 2009-02-04
    Age : 66
    Location : Texas

    Re: clone with one side not right

    Post by Luddite on Wed Apr 28, 2010 10:25 am

    Pete

    Check the two resistors paralleled with the input jacks. They should both be 470K ohms. From your photo, it appears that the right (red) channel input is indeed 470K, but the left (white) channel input is either 4.7K or 470 ohms. I can't quite make out the color of the third band on that resistor.

    Best Regards,
    Charlie

    natoe

    Posts : 34
    Join date : 2010-03-06
    Location : Pittsburgh, PA

    Re: clone with one side not right

    Post by natoe on Wed Apr 28, 2010 10:32 pm

    BOY do I feel dumb thats what it was. If it was a snake it would have bit me.Thanks for the help. next time i will put my glasses on.

    Sal

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

    Re: clone with one side not right

    Post by Sal on Thu Apr 29, 2010 4:25 pm

    ding ding ding ding ding....winner! bnc31 wins a prize.

    I posted the photos but truthfully I didn't look at them closely as I was busy restoring a Heathkit AA-100..... Usually its something simple very easily overlooked.

    Enjoy your amp.

    Sal

    wolverine

    Posts : 60
    Join date : 2010-02-20

    Re: clone with one side not right

    Post by wolverine on Fri Apr 30, 2010 7:50 am

    Just a quick suggestion on those IC caps.....I purchased a board and assembled it with those caps myself. It was a huge improvement in sound, in my amp anyway, to replace those caps with Orange Drops. The improvement was instant, it didn't take 200 hours of break in to tell the differences between the IC caps and the Orange Drops. Maybe something others here with more expertise could expound upon, but there was no question about the improvement in sound for my amp.

    wolverine

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