Repair Question - 2204 build - 120 Hz hum - FIXED! | The Canadian Guitar Forum

Repair Question 2204 build - 120 Hz hum - FIXED!

Discussion in 'Amp Building/Technical/Repair' started by SG-Rocker, Nov 26, 2019.

  1. SG-Rocker

    SG-Rocker

    Joined:
    Dec 30, 2007
    Location:
    Mount Polemic
    So I replicated my '83 2204 CSA in an old solid state 5010 chassis.

    Fired it up and no smoke, flip the standby switch and I get a 120hz hum.

    - the hum is constant and is not affected by the EQ, preamp or master volume;
    - pulling V1 and V2 makes no difference;
    - pulling V3, the phase inverter kills the noise completely.
    - removing the center lead from the master volume almost kills the hum
    - with the V3 installed:
    - removing the lead from pin 1 almost kills the hum
    - removing the lead from pin 6 almost kills the hum
    - removing either leads 2 or 7 reduce the hum volume a bit

    Any suggestions.... all grounding is as per the original amp.

    EDIT - Fixed.... forgot to ground the speaker jack sleeve to the chassis.

    THIS THING IS AMAZING !
     
    Last edited: Nov 26, 2019
    Lincoln, jb welder and greco like this.
  2. Lincoln

    Lincoln Gold Member

    Joined:
    Jun 2, 2008
    Location:
    Fort Saskatchewan, Alberta
    You gotta love it when a fix is something that simple.........and you spot it.......and it works!! :cool:
     

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