The Dynaco Tube Audio Forum

Would you like to react to this message? Create an account in a few clicks or log in to continue.
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


2 posters

    crackling in left channel

    MartinD18GE
    avatar
    MartinD18GE


    Posts : 1
    Join date : 2011-04-15
    • Post n°1

    crackling in left channel Empty crackling in left channel

    Post by MartinD18GE Sun Apr 17, 2011 4:07 pm

    I am a long time ST-70 user. It has been awhile since I have done any work on my unit other than changing tubes. Last week the left channel started making a crackling noise. Changing preamps didn't remove the noise. The 7199 on that side has always been sensitive. I pulled it and replaced it with a spare. The noise got worse. I removed the original PC-3 and replaced it with a 6GH8A board that I have had since the 90's. The unit was quiet for ten minutes, so I turned on the preamp. The crackling noise came back and stayed even after I shut off the preamp. I switched the tubes left to right and the noise stayed in the left channel.

    Does anyone have any thoughts? Am I looking at a quad filter cap, power supply or what?

    Thanks,

    Sean
    • Back to top
    Bob Latino
    Bob Latino
    Bob Latino
    Admin


    Posts : 3263
    Join date : 2008-11-26
    Location : Massachusetts
    • Post n°2

    crackling in left channel Empty Re: crackling in left channel

    Post by Bob Latino Sun Apr 17, 2011 5:05 pm

    Try cleaning that 7199 tube socket. The best stuff to use is Caig Pro-Gold. I think Radio Shack still sells it.

    After many years dust collects down in those tube sockets and sometimes you run into a partial contact issue with one or more socket pins. This is more common on 9 pin and 7 pin small sockets than the larger octal tube sockets found on the ST-70 output tubes. The reason being those little pins on the socket don't have much contact surface area and as such, they are more likely to give a partial contact problem.

    Years ago, when there was no Caig Pro Gold cleaner, what we did was to spray the PINS ON THE TUBE with WD-40 and wipe off the excess WD-40 so it's not drippy. Then insert the tube in and out of the socket a few times and then wipe off the pins until they are dry. Many times this will correct a contact issue between tube and socket. Sometimes you need two or 3 cycles of this procedure before the socket is completely clean.

    Bob
    • Back to top
      Current date/time is Tue May 07, 2024 6:45 am