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    PAS 3 loud hum/buzz

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    greggoad

    Posts : 7
    Join date : 2013-10-08

    PAS 3 loud hum/buzz

    Post by greggoad on Wed Oct 16, 2013 5:26 am

    I'm doing a pas3 rebuild with the new power supply, zmod pc6, Aikido pc5, and the PCB I/O

    I've clearly done something wrong.

    There is a constant hum/buzz that is loud, almost as loud as signal. I have isolated the ouputs from both phono amp, and the line amp and both have the same noise.

    In the instructions for the power supply, it says " a pair of wires about 6" long connected to the two holes marked 120vac" I'm assuming that this means one of these wires connects to one prong of the plug and the other wire connects to the other prong via the power switch? In the supplied diagram of old and new wiring i see two wires going through a hole, one for each side of the outlet. Are those the wires mentioned above?

    any other advice would be helpful. It seems to be an issue with grounding or the power supply...

    thanks.


    greggoad

    Posts : 7
    Join date : 2013-10-08

    Re: PAS 3 loud hum/buzz

    Post by greggoad on Thu Oct 17, 2013 2:14 am

    another question:

    should there be continuity between F+ and F- and H+ and H- on the contacts on the power supply board?

    Thanks.

    tubes4hifi
    Admin

    Posts : 1261
    Join date : 2008-11-30

    Re: PAS 3 loud hum/buzz

    Post by tubes4hifi on Sun Oct 20, 2013 7:19 pm

    answers and info sent via email

    mogman8

    Posts : 1
    Join date : 2015-10-24

    Re: PAS 3 loud hum/buzz

    Post by mogman8 on Wed Jan 06, 2016 5:35 pm

    What ended up being the problem with your PAS3? I just replaced the quad cap and removed the selenium rectifier per curacoaudio instructions as well as replaced the two big caps under the selenium rectifier on mine which cured the horrible distortion it had when I got it but now I have a loud 60hz hum. I'm not sure what to try next.

    Dale Stevens

    Posts : 77
    Join date : 2014-07-06
    Age : 67
    Location : Loris, SC

    Re: PAS 3 loud hum/buzz

    Post by Dale Stevens on Wed Jan 06, 2016 7:47 pm

    What answers and info?? Dale

    greggoad

    Posts : 7
    Join date : 2013-10-08

    Re: PAS 3 loud hum/buzz

    Post by greggoad on Wed Jan 06, 2016 7:55 pm

    Wow. This was a while ago... I have learned a lot since then. I never actually figured out what the problem was. I'm pretty sure however that I grounded incorrectly. I must have created a ground loop between the rca input shields and the circuit ground.

    The only advice I could offer is to check your grounds, make sure everything that is supposed to be grounded is grounded. And make sure that nothing is grounded that isn't supposed to be.

    Then make sure what ever grounding scheme you are using is not inadvertently creating loops, make sure components do not have multiple paths to ground.

    Good luck.

    tubes4hifi
    Admin

    Posts : 1261
    Join date : 2008-11-30

    Re: PAS 3 loud hum/buzz

    Post by tubes4hifi on Wed Jan 06, 2016 11:36 pm

    to MOGMAN8
    you have a grounding problem - missing ground?
    make sure your quad cap can is wired to chassis ground.
    all PCBs are connected to common ground point.
    All RCA jacks are grounded to common ground point.


    Last edited by tubes4hifi on Wed Jan 06, 2016 11:39 pm; edited 1 time in total

    tubes4hifi
    Admin

    Posts : 1261
    Join date : 2008-11-30

    Re: PAS 3 loud hum/buzz

    Post by tubes4hifi on Wed Jan 06, 2016 11:38 pm

    Dale,
    F+ to H+
    F- to H-
    check all grounds


    Greg
    you figured it out, everything grounded, with no ground loops (by using one common ground point for ALL ground connections)

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