The Dynaco Tube Audio Forum

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


    PAS-3 losing right channel signal

    Share

    lobby

    Posts : 18
    Join date : 2011-02-15

    PAS-3 losing right channel signal

    Post by lobby on 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!

    anbitet66

    Posts : 132
    Join date : 2009-12-23
    Location : Valley Stream, NY

    Re: PAS-3 losing right channel signal

    Post by anbitet66 on 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

    Bob Latino
    Admin

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

    Re: PAS-3 losing right channel signal

    Post by Bob Latino on 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

    Sal

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

    Re: PAS-3 losing right channel signal

    Post by Sal on 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

    lobby

    Posts : 18
    Join date : 2011-02-15

    Re: PAS-3 losing right channel signal

    Post by lobby on 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?

    lobby

    Posts : 18
    Join date : 2011-02-15

    Re: PAS-3 losing right channel signal

    Post by lobby on 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.








    tubes4hifi
    Admin

    Posts : 1282
    Join date : 2008-11-30

    Re: PAS-3 losing right channel signal

    Post by tubes4hifi on 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

    Sponsored content

    Re: PAS-3 losing right channel signal

    Post by Sponsored content Today at 5:35 am


      Current date/time is Sat Dec 03, 2016 5:35 am