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The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Tubes4hifi VTA tube amp and preamp kits and all Dynakitparts.com products


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    PAS-3 losing right channel signal

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    Posts : 18
    Join date : 2011-02-15
    • Post n°1

    PAS-3 losing right channel signal Empty PAS-3 losing right channel signal

    Post by lobby Tue Feb 15, 2011 2:26 pm

    Hi, first time posting here. I have a PAS-3 and recently I am experiencing the right channel starting to crap out. I am sure that all physical connections (rca) are tight. The right channel works intermittently, and usually if the volume is turned up, then down briefly, it will start to work again (for a short time). any clues on what might be the culprit?

    thanks!
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    anbitet66
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    • Post n°2

    PAS-3 losing right channel signal Empty Re: PAS-3 losing right channel signal

    Post by anbitet66 Tue Feb 15, 2011 2:45 pm

    I had a similar problem with my PAS-3x when I first got it. The seller said one channel would stop playing, he didn't mention that it would also have a loud hum, but that it did. I had to put the tubes back in their sockets when it arrived, and of course the problem was there. The cure was found by moving the tubes in their sockets. The intermittent connections caused by dirty pins, as well as weak sockets was all there was to fix. A good cleaning and re-tensioning of the socket connectors, as well as cleaning the tube pins permanently fixed it.

    Now, your mileage may vary, but you have nothing to loose. Try gently wiggling the tubes to see if the pins or sockets may be loose or dirty. Of course, you may need to inspect the wiring for defects, cold solder joints, etc.

    Let us know what you find.

    Tony
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    Bob Latino
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    • Post n°3

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    Post by Bob Latino Tue Feb 15, 2011 4:59 pm

    I think Tony is probably on to the correct issue with older PAS-3's. Since the tubes in the PAS are 9 pin tubes with small skinny pins, they are more sensitive to intermittant contact than larger octal tube pins which have more contact area on the pins.

    Years ago when there was no "Caig Pro Gold" or other contact cleaners I use to clean pins with WD-40. Spray directly on the pins of each tube and wipe most of it of so it's not "drippy" then insert the tube into and out of the tube socket about 5 times wiggling the tube around a bit. Do that to all the tubes and that should take care of any contact issue with the tube pins. If that doesn't cure the problem, look for either a bad capacitor on the line stage board (behind the tone controls on the front of the amp) OR a bad solder connection on the part of the board that handles the right channel.

    Bob
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    Sal
    Sal
    Sal


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    Location : Central New Jersey Dynaco-ST70.com
    • Post n°4

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    Post by Sal Wed Feb 16, 2011 11:32 pm

    Clean all the pots and switches while you are at it and also check for any cold solder joints or cracks on the pc boards.

    Sal
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    • Post n°5

    PAS-3 losing right channel signal Empty Re: PAS-3 losing right channel signal

    Post by lobby Tue Mar 01, 2011 4:03 pm

    There were no apparent cold solder joints and i cleaned the tube sockets with deoxit to no avail. Its not even intermittent anymore, it simply does not work. How long should this be unplugged for before the capacitors discharge? How do i check to see if there is a bad cap on the line stage?
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    • Post n°6

    PAS-3 losing right channel signal Empty Re: PAS-3 losing right channel signal

    Post by lobby Tue Mar 01, 2011 4:58 pm

    Here are some pics of the amp itself if that helps at all. One thing i did notice was kind of a rattling sound, MAYBE coming from one of the line stage caps.

    PAS-3 losing right channel signal Up1

    PAS-3 losing right channel signal Up3

    PAS-3 losing right channel signal Up33

    PAS-3 losing right channel signal Up4
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    Roy Mottram
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    • Post n°7

    PAS-3 losing right channel signal Empty Re: PAS-3 losing right channel signal

    Post by Roy Mottram Fri Mar 04, 2011 3:46 am

    looks like about half the caps have been replaced/upgraded, but why not the rest of them?
    Spend $15-20 and replace all those old caps, especially those blue .22 caps.
    Those 4 black ones are for the tone controls.
    BTW, somebody did a nice job rewiring the inputs to the selector switch,
    that's the kind of shielded audio cable I'm looking for, anyone know where I can get some like that?
    info@tubes4hifi.com
    www.tubes4hifi.com
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    • Post n°8

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