Subwoofer Power Supply Problem

[audiodane]

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.

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.

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.

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!

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

[seabrook]

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!

[thatscappy]

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?

[EricBJN]

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 !