Subwoofer Power Supply Problem

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  • audiodane
    New Member
    • Feb 2012
    • 2

    #81
    Re: Subwoofer Power Supply Problem

    Greetings. I also have a humming UFW-10 that's been sitting on my kitchen table for the last 4 months waiting for dissection (finally started humming after about 8 years). I finally had some time to look into it this weekend. Just found this thread today. I've submitted to Emotiva Audio (formerly Jade Labs) where the original amp design originated from, for a schematic and ideally a PCB layout as well, if they have it. If I'm allowed to share, I will do so. My hum is also only when certain RCA's are attached. For example, an iPod doesn't exhibit the problem because the iPod doesn't have a fixed ground reference, it's just an electrically-floating battery powered device. Anyway, I digress. My caps do not exhibit any visual signs of damage (no bulging or vented tops), but I'll be interested in removing them to see what their bottoms look like, based on Bob's post. I'll post back when I know more. I have two as well, and while the other is not humming (yet), I'll likely perform the cap replacement on both while I have all the tools out and setup.

    In the mean time, I thought I'd reply on a few others' posts.

    Originally posted by Chubber
    It's not going from standby to "on", which it should do if it sees a signal on the LFE input.
    One of my UFW-10's has developed a bad RCA connection. Resoldering the taps on the inside of the amp didn't help, so it must be some corrosion within the female portion of the connector. These amps are designed to go into "on" mode immediately after turning on (well, there's about a 5-10 second delay between applying power and the amp going "live"), and then going into standby after some amount of time (tens of minutes, not seconds) without a recognized signal. Try all your RCA inputs immediately after applying power. Also make sure you have a known good RCA signal.

    Originally posted by sfox
    I'm a new member with a busted UFW-10. Mine makes no sound at all. Has anyone tried modding one to use an outboard amp with the existing crossover & such? I have an old pro amp that would work well. Thanks!
    There are a few fellows that have done this, yes. I can't recall all of them at the moment. A few used to hang out over at Chase Home Theater (formerly Tweak City Audio). There was also talk about an updated woofer at some point, though not enough people were interested to make it reality.

    Originally posted by Bob in St. Louis
    A fellow gave me two of these Onix UFW-10 subwoofers because of the hum.
    Man I wish I had your friends...

    Thanks for the great pics, Bob!

    Originally posted by Bob in St. Louis
    My thought mehind using the DVOM on the cap was this....On the face of the voltmeter, the cap test happens to be the same knob position as the Ohm check.
    I realize your problem is solved now, but can you post a pic of your meter? On many meters, if the ohm-check is one color and the cap-check symbol is another color, there may be a button that swaps between the two functions. That's how my Fluke 189 operates. Turn the dial, hit the button, and boom you're in cap-check mode.

    cheers,
    ..dane

    Comment

    • seabrook
      Astro
      • Mar 2017
      • 1
      • USA

      #82
      Re: Subwoofer Power Supply Problem

      A quick success story:

      I just replaced the six highlighted power supply capacitors (47 microF, 470 microF and 1000 microF) and now the AC hum is gone! After several years of being sidelined and nearly being tossed my ULW-10 has risen from the ashes like a Phoenix!

      Thank you all, thank you!

      Comment

      • thatscappy
        New Member
        • Feb 2021
        • 2
        • united states

        #83
        Re: Subwoofer Power Supply Problem

        Okay so I got one of these and the guy offhandedly mentioned that there was a bit of a tone when starting it up. I tried it out and it was playing what sounded like a real tone from a synth pretty loud. So I found this forum and bought 2 1000uf 25v capacitors to replace in the unit. They were definitely bad looking. I replaced them and started it up and, well, the tone is now gone. But unfortunately it looks as if it's still not working. So now I am wondering, what's next?

        Comment

        • EricBJN
          New Member
          • Dec 2021
          • 1
          • France

          #84
          Re: Subwoofer Power Supply Problem

          Hi to everybody,

          This is just to thank you: I replaced the 6 caps that were very bad and my sub is working fine now.
          This forum is great !

          Comment

          • EugeneC
            New Member
            • Mar 2025
            • 2
            • Australia

            #85
            Signed up to say thanks to all those who contributed to this thread for the past 15+ years. I was experiencing a constant hum with my subwoofer, and while the plate amp was not the one described in here, it appears that the power supply PCB used by the Woofers by Bob Carver Dominator Model D-10 uses the same (or extraordinarily similar) PCB. The board in this case is labelled JUNIOR V1.2 POWER SUPPLY

            One of my two caps looked slightly bloated, and it matched the regularly discussed 1000uf 25v ones in this thread. I replaced both on my board, and no more hum!

            Including some pictures in case they can help others in the future. Especially for others who have Bob Carver dominator subwoofer amps that might not be aware that this thread could help.

            The bloated cap:
            Click image for larger version

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            The Junior v1.2 PCB with the caps in question circled in blue:
            Click image for larger version

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            The bottom side of the PCB with the solder points for the caps in question circled in blue:
            Click image for larger version

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            Replaced caps:
            Click image for larger version

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            The Woofers by Bob Carver Dominator D-10 Subwoofer Amp
            Click image for larger version

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            Comment

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