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Kenwood indash noise problem?


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rodneydtracy 
Member - Posts: 10
Member spacespace
Joined: March 21, 2005
Location: United States
Posted: October 04, 2006 at 2:50 PM / IP Logged  

OK, I need some help. My stepdad's system is pretty simple, 4 6x9's, a 12" sub, and a 5 channel kenwood amp. He had a Kenwood KDC-s5009 indash, and I recently tried 'upgrading' him to a KDC9015 I had sitting around.

Here's the thing I can't figure out: With the original indash the system sounded great. With the new one I get this mild high pitched noise with the car off and an obnoxious alternator noise with the car running. I put the old indash back in, no noise. All the wiring is the same, I even tried using the older unit's wiring harness with the newer unit (they are the same harness) and the noise is still there.

The noise doesn't go away if I unplug the antenna, or in I leave the antenna pluged in and unhook the ground wire. It is still there if either the front or rear RCAs (or both) are hooked up.

Oh, I forgot, the newer unit also has the kenwood dashtop display unit and compass that go with it, but the noise is still there even with that unplugged.

It is really annoying, because the 9015 looks great and all the features work on it.

It is all installed in a '93 Dodge Ramcharger, if that makes a difference.

I looked through the forum, and couldn't find a problem like this one, can anybody help?

sparkie 
Platinum - Posts: 2,061
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Joined: November 06, 2003
Location: Canada
Posted: October 04, 2006 at 3:26 PM / IP Logged  
If all you do to create the noise is swap the head unit from one to another, then the problem is inside the head unit. There may be a bad connection inside that affects the pre-amp section. This area is very suceptible to noise if it isn't shielded or grounded correctly. It could be just a bad tracer on the circuit board.
sparky
geepherder 
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Platinum spaceThis member consistently provides reliable informationspace
Joined: October 27, 2003
Posted: October 04, 2006 at 5:12 PM / IP Logged  
Bingo. The rca outputs on the head unit have a bad ground, hence the noise. This problem is very common with Pioneer units. If it's still under warranty, have it repaired. If it's not, you can ground the outer shields of the rca's at the deck, which should eliminate the noise.
My ex once told me I have a perfect face for radio.
rodneydtracy 
Member - Posts: 10
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Joined: March 21, 2005
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Posted: October 04, 2006 at 5:28 PM / IP Logged  
What should they be grounded to?
i am an idiot 
Platinum - Posts: 13,693
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Location: Louisiana, United States
Posted: October 04, 2006 at 5:39 PM / IP Logged  

    Take a short length of small wire ground one end of it and then strip a few inches of the other end then wrap this around the shield of your rca jack.  Chances are any one of them will fix your problem, but you might have to do all 3 sets.   you can do this at the amp or at the radio.

rodneydtracy 
Member - Posts: 10
Member spacespace
Joined: March 21, 2005
Location: United States
Posted: October 04, 2006 at 6:12 PM / IP Logged  

I'm not trying to be dense, but I need a little clarification. You want me to take a length of wire, ground it to the chassis, then wrap it around the outside of the female RCA jack on either the indash or the amp? If so, what do you mean about all three sets? (The indash has only front and rear RCAs, each with right and left sides.) If I am understanding correctly, then do I just connect the RCAs to the length of wire and RCA jacks and all?

The plug that connects the RCAs to the board inside the indash has three wires (white, red and black) for each (front and back.)

If I am supposed to ground to the chassis, can I use the same ground as the indash?

Is this a permanent fix? Will it cause any damage? I thought that letting the RCAs touch a ground was a no-no?

i am an idiot 
Platinum - Posts: 13,693
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Joined: September 21, 2006
Location: Louisiana, United States
Posted: October 04, 2006 at 8:17 PM / IP Logged  

You said you had a 5 channel amp    I was assuming you had a front rear and sub out.

Yes just ground one end to the ground wire of your deck or your amp   then strip a few inches of the insulation off the other end exposing the wire,  take the wire and wrap it around the outer metal part of your RCA jack then twist it like a bread tie.     Yes this is a temporary fix.  The outer part of an RCA jack is Ground so no it does not affect anything if it touches Ground.

   There is a burnt trace on the inside of your radio.   This happened by 1 of 2 ways.  Either a 12 volt wire touched the outer part of your patch cord.  Or at some time in the life of the radio someone hooked power to an amp then hooked the RCA jacks up before they hooked the ground wire to ground,  When power was hooked to the amp it began looking for ground which it found via your RCA jack, and it could not handle the current, thus opening a trace on the circuit board.

    

i am an idiot 
Platinum - Posts: 13,693
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Joined: September 21, 2006
Location: Louisiana, United States
Posted: October 04, 2006 at 8:21 PM / IP Logged  

            If you have access to a meter  take your old radio   the one that works       put the meter on the lowest ohm scale    touch one lead to the chassis of your radio and the other to the outer part of the RCA cable   it should and will read less than 10 ohms              do the same on the other radio   unhooking the patch cords that go to the amp    this radio will read nothing or a very high number

rodneydtracy 
Member - Posts: 10
Member spacespace
Joined: March 21, 2005
Location: United States
Posted: October 05, 2006 at 3:49 PM / IP Logged  

OK, first of all I borrowed a meter, and I think I had it on the right settings--the new radio (9015) I got no readings, the old radio (s5009) I got readings that jumped around a little, but were under 10. ( I am assuming I was sopposed to check it without being connected to the car.)

So, the wiring. First I used two seperate wires, one for the front RCAs and one for the rears. I wrapped each one around the right channel RCA and then around the left, and then connected the other end to the factory ground strap that the radio was grounded to. The noise didn't go away, in fact when I unhooked the wires and then re-touched them to the ground it actually got worse with them connected.

I did all of this at the indash end of the patch cords, if that helps.

Help!

rodneydtracy 
Member - Posts: 10
Member spacespace
Joined: March 21, 2005
Location: United States
Posted: October 05, 2006 at 3:52 PM / IP Logged  
By the way, I used a speaker wire, if that makes a difference.
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