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-   -   high pitched noise (http://www.diyaudio.com/forums/car-audio/157643-high-pitched-noise.html)

candyman122 31st December 2009 06:27 AM

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).

I Am An Idiot 31st December 2009 08:42 AM

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.

candyman122 31st December 2009 01:57 PM

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.

candyman122 2nd January 2010 01:56 PM

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...

Perry Babin 2nd January 2010 05:50 PM

Is the noise/fault causing any problems other than being audible?

jol50 4th January 2010 01:37 AM

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

candyman122 7th January 2010 02:08 AM

Quote:

Originally Posted by Perry Babin (Post 2032307)
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

Perry Babin 7th January 2010 02:13 AM

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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