Subwoofer Hum problem - AVS Forum
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post #1 of 7 Old 10-09-2012, 10:02 PM - Thread Starter
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First let me say that this is my first post, so if I forget to include specific details or something else, forgive me.


Background info:

I've had a Mirage Nanosat 5.1 Surround Sound System for a couple of years now and it's worked beautifully up until a few days ago. I was watching netflix through my PS3 when suddenly my Subwoofer (began humming, very loudly I might add. I've done some trouble shooting and found it's something with the sub itself as it makes the hum with and without the audio cable (will hum if the only cord attached is the power cord). At first I thought it was a ground loop problem; however, after letting it discharge and opening it up I can't find anything wrong with it. I also tried another outlet in another room (in case another device was interfering, as I read could be an issue), still hums.

Here's a picture of the inside (if it helps), not sure what that white stuff on the side is.




If anybody knows anything, that's be great. Otherwise it'll be off to the repair shop.


Thanks
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post #2 of 7 Old 10-10-2012, 12:38 AM
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A hum like this is most often associated with a failure in the power supply. Unfortunately, troubleshooting that is something a novice would find difficult at best. From the photo it looks like a bipolar analog supply, which are the easiest to work with, but I can't give you much more than that. You might see if there's a service manual online, or I would suggest having the thing serviced. I use a particular guy for amp servicing, but he's in California, perhaps that's not good for you. I ship stuff to him, he fixes and sends back. Doesn't seem to matter what it is. PM me if you need his contact.
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post #3 of 7 Old 10-10-2012, 09:42 AM - Thread Starter
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Well darn, thanks for the reply, i'm a few states away from California so that won't work for me, but thanks anyways! Guess it's off to the local repair guy.
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post #4 of 7 Old 10-12-2012, 10:27 AM
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The white stuff appears to be thermal paste, used to assist in transferring heat from the output transformer to the heat sink.
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post #5 of 7 Old 01-18-2013, 12:18 PM
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ngilmore, I'm facing the very same issue with my Mirage Nanosat 5.1 Subwoofer. Have you located the issue and/or the solution yet?
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post #6 of 7 Old 02-03-2013, 03:04 PM
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Hi,

I'm just responding to the thread about the hum in Mirage subwoofers. I have a customer who brought in a Mirage Omni 8 with major hum. The speaker is at full excursion when the woofer is plugged in and either on or in auto. I suspected the power supply. Upon examination I found the main caps to be swelled. I replaced them and still same issue. I tested every component in the main amp board due to the fact that this company does not supply a schematic or any support other than replacement parts that are expensive and sometimes not available. I found no failed parts in this unit. The only thing I have not tested is the transformer. I suspect that there is a bad winding and possible straight AC is getting through. I cannot find the rating of this transformer and short of replacing this, I feel this unit is not worth fixing.

mike
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post #7 of 7 Old 02-03-2013, 03:50 PM
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Quote:
Originally Posted by Solid State Amp View Post

Hi,

I'm just responding to the thread about the hum in Mirage subwoofers. I have a customer who brought in a Mirage Omni 8 with major hum. The speaker is at full excursion when the woofer is plugged in and either on or in auto. I suspected the power supply. Upon examination I found the main caps to be swelled. I replaced them and still same issue. I tested every component in the main amp board due to the fact that this company does not supply a schematic or any support other than replacement parts that are expensive and sometimes not available. I found no failed parts in this unit. The only thing I have not tested is the transformer. I suspect that there is a bad winding and possible straight AC is getting through. I cannot find the rating of this transformer and short of replacing this, I feel this unit is not worth fixing.

mike

You can figure out the rating of the transformer by the Amp the Mirage uses, for example a STK or STA etc. the look for the data sheets on the amp and it should tell you what the
Range of voltage the amp will accept. Also the transformer should only step down the voltage from 120 or 230 to just above what the Amp chip will accept in DC. The transformer would
have to go through a rectifier to get to that DC voltage. So you can test the AC voltage before it gets to the Rectifier and then after in DC.

Athanasios
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