Stanphill
Well this seems like the place to go for the MFW needs, so thought I would post this up and begin here.

I've owned a MFW-15 for a while now, but for a very long time it simply sat there unused due to other matters totally unrelated.

It worked, but had a nasty hum -- now just recently it was put back into use and it died.  Everything was turned off except the switch on the back of the sub-woofer and out of nowhere it made a seriously loud buzzing, then shut off and now there is no power.

My first reaction was to go back to av123, but to my surprise (horror?) they are no longer around.

My knowledge of these is really rather limited, so I haven't cracked the thing open yet.  I know the amps have had their issues and that was my first thought as to what happened.

Is there a way to tell exactly what is wrong?  Amp ? some other board? the driver?

I went looking around and saw the Turbo upgrade, but that may be a bit pricey right at the moment.  Is there any other reliable options out there if I can figure out exactly what I need?

I know - a lot of questions, but I appreciate any help to these that anyone can offer.

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nottaway
I would start with removing the amp.  Do you know if its V1 or V2?  The V1 should have driver leads soldered to the amp board, v2 should have spade connectors to the amp board.

Push in evenly with both hands on the driver evenly distributing force in a circular shape and see that driver is free and noise friction free.

After you remove amp test driver with a battery, AA, C, D really doesnt matter connect driver wires to the battery and listen for a staticky thud when you connect them.  If pushing on driver and testing with battery test good I would suspect amp.

Inspect all caps/resistors for burn out, and perform cap mod if its a V2 before doing anything else.

Murrel has a few V3 amps left so look him up on here or AVS or Simply sound.com  I like the V3 amps better than the V2 for sure.

Check fuse where IEC connector connects but if you have blown fuse then other problems are present.
AKA NicksHitachi
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Stanphill
Excellent info, thank you very much.

Going to crack it open and check.  The battery thing would have never crossed my mind as a way to see if the driver was any good.

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Murrel
Thanks Nick!

You know I missed this post and I am sorry. I am in the middle of a move so I have not spent as much time online. 

Stanphill,

You have a PM

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erhein
I just recently moved my MFW-15 which has Murrel's V3 amp.  Now when I connect the subwoofer pre-out from my receiver to the LFE input on the MFW-15, I get a low level hum which was not there before.  It's loud enough to be heard when there is no audio, program material, but not loud enough to be heard above program material.  Any suggestions?
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Murrel
erhein wrote:
I just recently moved my MFW-15 which has Murrel's V3 amp.  Now when I connect the subwoofer pre-out from my receiver to the LFE input on the MFW-15, I get a low level hum which was not there before.  It's loud enough to be heard when there is no audio, program material, but not loud enough to be heard above program material.  Any suggestions?

erhein,

If you remove the LFE cable from the sub is the hum still there? If it hums even with the cable removed from the sub then we have a amp problem. If it only hums with the cable connected then there is a problem within the system. Could be a bad cable or a ground loop.

I am always available. So if you like you are more than welcome to call me.

The number is on the front page of my web site. Yes it is my personal cell so I will answer it almost any time as long as I am awake!


Murrel
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erhein
Thanks for offer, Murrel.  I found the culprit.  It's the projector.  When I plug in the projector, which has a 3 prong plug, the hum starts.  It's certainly a ground loop.  I've heard bad things about cheater plugs, but is it all that dangerous if I try a cheater plug from the projector into the power conditioner that the projector is plugged into?
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Murrel
erhein wrote:
Thanks for offer, Murrel.  I found the culprit.  It's the projector.  When I plug in the projector, which has a 3 prong plug, the hum starts.  It's certainly a ground loop.  I've heard bad things about cheater plugs, but is it all that dangerous if I try a cheater plug from the projector into the power conditioner that the projector is plugged into?

erhein,

I have run cheater plugs many times. I understand the potential risks. We use them all the time in pro audio. In fact I have probably 200 plus at my brew and blues pub. I use them to eliminate hums on stage. No one has ever been electrocuted. 

Here is a suggestion that has worked for some in the past.

If your sub is close to the receiver it is a easy thing to try. 

Make a single wire with crimp lugs on both ends (forked style). hook one end to the ground (phono or antenna) on your receiver and the other end to one of the amp mounting screws on the amp plate. make sure that you bare the metal under the mounting screw. I personally have never had a hum so I have never tried this. I have had a few customers say that this has fixed the low level hum that they had.

It is your choice with regards to the cheater plug. 

Let me know if I can help

Murrel


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erhein
Okay, cheater plug is installed.
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