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    st-70 with no stereo seperation

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    mattst3

    Posts : 4
    Join date : 2010-03-05
    Location : Pennsylvania

    st-70 with no stereo seperation

    Post by mattst3 on Wed Feb 09, 2011 9:37 pm

    Hi, I recently came across an ST-70 that has no stereo operation. When I set the preamp balance control to the center, things sound okay but no seperation. When I move the balance to either right or left the sound volume goes down slightly but still hear equal sound volume from each channel, although a little distorted at higher volumes. I also notice that when I turn the volume to off, I can still hear output only very low. I have three other ST-70s and I have never experianced this kind of thing before. I have tested with two differant working preamps ( PAT-4 and Marantz 7T-set to low output). I have a PAS-3 also but am afraid to try since something is wrong with this amp. I tried to run one channel at a time with an RCA shorting plug in the the unused input with the same results. I disconnected the mono/stereo switch per Bob Latino's diagram and still no effect. I was told this amp was home built so I went through the factory wiring directions and checked each wire. I found a few cold solder joints and repaired them but found no wiring errors. I was told this amp was sitting in a basement, maybe damp seeing some rust on the cover. I wonder if the power transformer is damp or shorting? Any ideas would be appreciated.

    Bob Latino
    Admin

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

    Re: st-70 with no stereo seperation

    Post by Bob Latino on Thu Feb 10, 2011 7:48 am

    Hi,

    See if you can post a photo of the interior wiring of this amp on the forum here. Maybe one of us can pick up on some wiring issue that could cause your amp to stay in mono. You will have to host the photo on some other web site because this forum can't host a photo. You could also post a link to the web address to the photo.

    Bob

    Sal

    Posts : 221
    Join date : 2009-02-05
    Location : Central New Jersey Dynaco-ST70.com

    Re: st-70 with no stereo seperation

    Post by Sal on Thu Feb 10, 2011 12:49 pm

    You can email me a photo of the top and bottom of your amp and I will post it here if you like.

    Sal

    salb203 at optonline dot net

    mattst3

    Posts : 4
    Join date : 2010-03-05
    Location : Pennsylvania

    st-70 with no stereo seperation

    Post by mattst3 on Thu Feb 10, 2011 5:50 pm

    Thanks, I'll try to take a picture of the top and bottom as best as I can.

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