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Old 28th May 2012, 12:55 AM   #1
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Default kenwood head unit pre outs problem

i have a kenwood kdc-bt645u head unit that has all kinds of messed up sound coming through over the front and rear preouts. even with the car off. out of all the trouble shooting ive done, the only thing that seems to have cured this is if i run a chasis ground to the negative of the pre outs. i opened the unit up to see if i saw anything that appeared burnt or damaged. the internal amp works fine also.
ive tried all the basics and narrowed it down to the head unit (which was the last thing i thought it would be)
should i just solder a ground to the pre outs to resolve this? or is there something in the head unit itself that needs replacing?
thanks so much for your time
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Old 28th May 2012, 01:05 AM   #2
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RCA Shield Repair
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Old 28th May 2012, 01:16 AM   #3
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thank you, that helps a ton. needless to say im a bit agervated, especially since i removed my amps and subs initially to find the problem. and gutted one of my amps to find that there was nothing wrong with it.
i appreciate your time
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Old 28th May 2012, 08:20 PM   #4
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ok,,im sort of back to where i started. seems that it was my head unit, but also my amp. ive bench tested my amp and i get noise coming through the speakers. i found the blown ground sheild in my head unit and fixed that but aparently one of my amps is having the same issue. problem is, im not sure if amps have the same type of sheild or w/e its called. its a old amp, mtx 4300x. ive had to repair the legs on the rca connectors in the past, they are still good. should i run a ground from the rcas to the ground on the amp also? seems the chasis of the amp isnt part of the circuit, not sure if it is suppose to be though....
thanks
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Old 28th May 2012, 08:53 PM   #5
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What model kenwood amp?
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Old 28th May 2012, 09:15 PM   #6
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its a mtx 4300x but i think it has more issues than just the noise, seems to not be putting out any power to the speaker outputs. when i hook something up to the rca inputs i can barely hear it coming through the speaker. im at the point of giving up, i wasted my whole day screwing with this dam thing.
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Old 29th May 2012, 04:45 AM   #7
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Sorry. I should have read more carefully.

Does the head unit work properly with your other amp?

Do you have a scope?
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Old 29th May 2012, 10:13 PM   #8
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no scope, just a multimeter. yes my other amp works fine with my head unit. what initialy seemed to be the source of all this was the rca jacks on my other amp were missing the screw that secures them. the rca sheild in my head unit was bad, but i fixed it. seems that when my head unit took a hit, so did the amp.
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Old 29th May 2012, 11:55 PM   #9
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What are you using for a 12v power supply?
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Old 30th May 2012, 12:06 AM   #10
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to bench test it? if so, a car battery that i have hooked into my batt backup for my pc. otherwise, im using the batt in my car
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