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Amp frying fuses - help appreciated #2416734
06/04/12 08:22 PM
06/04/12 08:22 PM
Joined: Jan 2012
Posts: 2
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Sub1ime14 Offline OP
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Sub1ime14  Offline OP
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Joined: Jan 2012
Posts: 2
Firstly, thank you in advance to anybody who responds. If this is in the wrong area, mods, I apologize - please of course move it to a proper location.

I recently borrowed a Mackie FR800 power amp from a friend and used it for a few weeks with no issues. Upon returning it, of course one of the channels would not work for him (Ch1).

Opening the case, two of the fuses looked bad. Replaced them with 10A fuses (same as stock), and powered on. The ceiling lights in my garage went dim for a moment upon powering the amp on, and one fuse fried within less than a second. Channel 1 of course still does not work. Channel 2 operates with no issue (before and after the fuse swap - appears to be utilizing the other 2 fuses and is unaffected by the issue).

Any ideas what this may indicate? Perhaps something is grounding out or surging somewhere? I'm attaching a few pictures for reference. The fuses are in the back left corner. I'm just not sure where to start.

Pics are on my WebShots at:
http://community.webshots.com/album/582912042lClSps

Thank you.

Re: Amp frying fuses - help appreciated [Re: Sub1ime14] #2419379
06/15/12 09:32 AM
06/15/12 09:32 AM
Joined: May 2001
Posts: 782
Prince George,CANADA
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audiofreek Offline
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audiofreek  Offline
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Posts: 782
Prince George,CANADA
Make sure you have a load on the amp(speaker connections verified) before powering it on.A minimum load of 2 Ohms is crfitical,most amp failures are caused by insufficient load.Make sure al DIP switches are in the proper locations according to the manual,moving the switches around,making sure they are seated in the proper locations.If that doesn't work send it to a Mackie tech for repair.

Last edited by audiofreek; 06/15/12 09:36 AM.
Re: Amp frying fuses - help appreciated [Re: audiofreek] #2801522
09/03/16 09:46 PM
09/03/16 09:46 PM
Joined: Aug 2016
Posts: 45
GA, USA
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SteveVasil Offline
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SteveVasil  Offline
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There are a few things which might be checked with the power cord unplugged. You might be able to narrow down the problem fairly easily, as you have a "good" side and a side that will be reading bad compared to the good side. I'd check the output transistors or output I.C.s with an ohm-meter/diode checking function of a multimeter, comparing them to the ones on the working side. Often, these are screwed to a heat-sink, a piece of metal like aluminum to help dissipate heat. Do you have a schematic? Keep in mind while I've done some repair work, I'm not familiar with your particular amp.

Re: Amp frying fuses - help appreciated [Re: SteveVasil] #2801523
09/03/16 09:49 PM
09/03/16 09:49 PM
Joined: Aug 2016
Posts: 45
GA, USA
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SteveVasil Offline
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SteveVasil  Offline
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Joined: Aug 2016
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GA, USA
Also, again with the unit unplugged, if you suspect a component is bad, smell it. A burned smell may help confirm your suspicion. Look over everything closely; it could be something as simple as a wire touching ground or frame that shouldn't.


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