This is topic Stereo guys, need help! in forum Tech Talk at Northern California Ford Owners  .


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Posted by wilit (Member # 3367) on :
 
My car is a '68 Mustang with an '85 HO & alternator.

I had an old JVC head unit that worked well, but I was tired of keeping 300 CD's in my car. So being the cheap bastard I am, I picked up a cheap radio/mp3 player head unit at Fry's for $30. Wired it exactly as the old JVC which never had a buzzing problem. When I turn on the engine, there's a buzz in the speakers. It's not like a normal alternator whine because it doesn't change pitch as the RPM's go up. It's just a steady buzz. I checked the ground for the head unit, redid the engine ground and installed a filter on the + side. Still got the buzz.

I found that if I remove the radio from the mount, there's no buzz. As soon as I mount it back in the dash, buzz. I tried insulating the mounting bracket, but it works for a little while, then vibrates and I get the buzz back.

Besides buying a better radio, what can I do to isolate the buzz?
 
Posted by SteveL (Member # 1241) on :
 
quote:
I found that if I remove the radio from the mount, there's no buzz. As soon as I mount it back in the dash, buzz.
Sounds like a ground loop problem (more than one ground and one of them isn't a good one).

If you have some speaker wire available, try running a wire from the mounting bracket to the same point the head unit ground wire is connected to. Just something to try to see if it eliminates the buzzing.
 
Posted by wilit (Member # 3367) on :
 
quote:
Originally posted by SteveL:
quote:
I found that if I remove the radio from the mount, there's no buzz. As soon as I mount it back in the dash, buzz.
Sounds like a ground loop problem (more than one ground and one of them isn't a good one).

If you have some speaker wire available, try running a wire from the mounting bracket to the same point the head unit ground wire is connected to. Just something to try to see if it eliminates the buzzing.
If I ground the bracket, I get the buzz. If I don't ground the bracket, no buzz. The problem I have is, it's a '68 and the radio bezel and dash are all metal, so there's no way to insulate them to keep from grounding the bracket.

Right now the harness is grounded to the dash. Do you think if I ran the ground all the way to the battery it might get rid of the buzz?

[ 2013-06-12, 08:25 PM: Message edited by: wilit ]
 
Posted by SteveL (Member # 1241) on :
 
Are you grounding the bracket to the same point where the wiring harness is grounded to? It's doesn't need to be the (-) side of the battery, it's where the (most likely green) ground wire from the radio harness is connected to the car. The idea is to connect the chassis ground (the radio case/bracket) to the same point as the electrical ground (the ground wire in the wiring harness).

Another test for a ground loop: Disconnect the ground wire in the harness. Mount the radio in the bracket so it's grounded using the radio case. See if that buzzes. If it doesn't, you might be able to just use the bracket for a ground.

[ 2013-06-13, 07:46 AM: Message edited by: SteveL ]
 
Posted by wilit (Member # 3367) on :
 
I think it's a head unit issue. I tried everything you suggested, still the buzz. I hooked up the old head unit, no buzz. I looked up some reviews on this thing and everyone says it's got the buzz no matter what they do. So looks like it's time to return it.

Thanks for your help!
 




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