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Old 31st December 2009, 06:27 AM   #1
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Default high pitched noise

Need some help figuring this out. I have a kenwood kac-9104d that had a loose inductor soldering. By the time I spotted it, the power supply burned out. (not sure if that's related). I replaced the power supply fets and resoldered the inductor. It powers up, and plays, but after a few seconds I get this high pitched whine noise coming from the amplifier itself. I'm not sure from where, I can't pinpoint. If I disconnect the speakers and the headunit, I still the get noise. I tried moved the inductors and transformer around, retouched the soldering, but to no avail... I'm afriad to look at waveforms or measure voltage while the noise is happening so I don't burn more things up. (i do have a 2ohm resistor in B+ line).

Last edited by candyman122; 31st December 2009 at 06:32 AM.
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Old 31st December 2009, 08:42 AM   #2
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If you leave it on for 10 seconds, does the resistor get hot? Do not touch the resistor, just hold your hand directly above it.
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Old 31st December 2009, 01:57 PM   #3
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No, the resistor doesn't get hot. No excessive current drawn. As I played with it more, it seems that when the amp has rested for a while and is "cold" I can have it play longer, sometimes over a minute before I hear the noise. When it's warm, it's almost immediate. Nothing really gets hot in the amp though. The only things that got warm/hot a few times were the a1859 and c4883. Are these drivers or regulators? They are mounted to the heatsink.
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Old 2nd January 2010, 01:56 PM   #4
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Default transformer

So I figured where the noise comes from, it's from the laminated core transformer. If I move it around or put a lot of pressure on it, it stops the noise. I took it out, and looked at the wires, I didn't see anything out of the ordinary. I resoldered and still the same; however, I can get it to play for a long time once I set it "right." Where can I get a replacement? Or should I try to just glue it down? But then if that doesn't work, it's gonna be hard to remove it...
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Old 2nd January 2010, 05:50 PM   #5
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Is the noise/fault causing any problems other than being audible?
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Old 4th January 2010, 01:37 AM   #6
jol50 is offline jol50  United States
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I have a 2.7 ohm 50w alum resistor, it works nice for that I hold my hand right on it. It will not get too warm too fast, and I have a volt or amp meter so I know if the amp has an issue. I use a 2 ohm resistor for more power. Most kenwood have low idle current, some larger or high idle current amps will not run on the 2.7 must be why everyone said get a 2 ohm, lol, but it works nice for smaller amps or to medium class d I use it all the time. Mouser 284-HS50-2.7F
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Old 7th January 2010, 02:08 AM   #7
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Quote:
Originally Posted by Perry Babin View Post
Is the noise/fault causing any problems other than being audible?
No, it doesn't appear so. I let it run with the nosie and the noise dies eventually. Just sometimes it's gets super high and very annoying for seconds and varies tone and loudness. Kind of sounds like those annoying mosquito buzz ringtones, only amplified
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Old 7th January 2010, 02:13 AM   #8
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If it doesn't appear to be causing problems and won't be audible when reassembled and in the vehicle (under the seat or in the trunk), it's probably not worth troubleshooting.
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