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Old 29th July 2012, 03:34 PM   #1
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Arrow Kenwood KAC-X811D, Low power output

Hi Guys,

I'm new here and I would like to fix this my self, so I'm really hoping someone can help me.

I have a Kenwood KAC-X811D it WORKS! but it has very low power output. I think some FETs are gone.

I have it all set up right, gain, volume, speaker, power wire.
I have opened it up and I don't see any physical damage.

I think it might be the power FETs Q57,58,60,61,64,65,67-70
or the amp FETs Q48-51

Do I have to remove them to check them?
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Old 30th July 2012, 12:01 AM   #2
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How do you define low power output? Low volume but clean, low volume and distorted...
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Old 30th July 2012, 01:10 AM   #3
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Low volume clean, the display is reading around 3 amps and has a measured voltage of 35. So it sounds and is about 100watts.
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Old 30th July 2012, 01:39 AM   #4
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Are you sure that the woofer isn't defective?

35v is over 300 watts into 4 ohms and over 1200 watts into 1 ohm.
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Old 30th July 2012, 11:49 AM   #5
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But at 3 amps its only 100watts. I have no reason to believe the woofer is defective. It seams to me its an amperage problem.
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Old 30th July 2012, 12:49 PM   #6
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So the VAS seams to be OK, but the output stage is defective?
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Old 30th July 2012, 09:44 PM   #7
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The amp is hooked up 2ohm to a 300watt RMS woofer. If this was working correctly it should be destroying the woofer, but it hardly moves, sounds like ~100watts.

I never thought if I asked for help I would get help from Perry Babin... I have been reading your entire webpage religiously over the passed few months. Thanks!
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Old 30th July 2012, 11:42 PM   #8
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Disconnect the woofer from the amp and measure the resistance across the speaker wires. Post the resistance.
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Old 30th July 2012, 11:49 PM   #9
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I measured it before. I don't have the exact number but it was very close to 2ohms.

The speaker was at 8ohms (Dual 4ohm VC) and it was not very loud, so I changed to 2ohm and no noticeable change in volume.
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Old 31st July 2012, 12:12 AM   #10
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2.1ohms
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