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Perc
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Loud pop when turning car stereo off and on

So... I just decided to go for a drive. I started the car and noticed that it misfired slightly. I turned the volume down to hear the engine better, but the misfire disappeared so I didn't really give it any more thought. About 10 seconds later when I turned the volume back up, all I heard was a loud whine that seemed to follow the engine revs. I turned the stereo off and on again immediately.

The whine disappeared, but I'm left with a loud pop from the speakers whenever the stereo turns on and off, when I change the radio channel, or when I turn the volume knob one notch up from 0, or back down to 0. The volume knob is digital, not just an analog dial. I guess the problem has to be in the stereo itself since it does it regardless if the engine is running or not.

The stereo works fine otherwise. No reception problems and the CD player works fine. The car runs fine otherwise. No misfires or anything.

I tried leaving the battery disconnected for about 45 minutes, didn't make a difference.

The car is a 98 Volvo V70. The sound system is completely stock - a Volvo SC-900 head unit (built in 3-disc changer, tape deck etc) and a volvo auxiliary amp under the passenger seat.

I really hope the head unit isn't fried. I really like the look, sound and ease of use and getting an aftermarket deck to play well with the rest of the system is probably not the easiest thing in the world. I took the head unit out and found a round connector with about 6 pins marked "AMP", another connector with about 10 other wires that I assume are for power, backlight (the stereo backlight is connected to the dashboard dimmer) and whatnot. There are two coaxial antenna connectors too, a smaller one marked "SUB" and a regular one marked "MAIN".

hep?
Old 08-09-2008, 10:03 AM Perc is offline  
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dbu8554
 
yeah dude the electrical system of your engine is interfering with your sound system sounds like really really common on cars from the 70's and older anyways don't know what is involved with fixing it just letting you know what it is .
Old 08-09-2008, 10:08 AM dbu8554 is offline  
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Perc
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Originally Posted by dbu8554 View Post
yeah dude the electrical system of your engine is interfering with your sound system sounds like really really common on cars from the 70's and older anyways don't know what is involved with fixing it just letting you know what it is .

Did you even read my post? The alternator (or whatever) whine disappeared after I "rebooted" the stereo. However, I'm now left with a loud POP whenever the stereo turns on and off (and when changing channel etc) regardless if the engine is running or not. My car is also from 1998, not 1978 and it worked fine yesterday and earlier today.
Old 08-09-2008, 10:15 AM Perc is offline  
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DvBoard
 
Sounds like the radio may be on the way out, or that may just be a qwirk of it. The "pop" you hear is just energy going to the speakers when they first turn on. Why it suddenly started doing it, i dunno.

Your not having trouble starting the car or anything are you? I just replaced the battery in my '98 Cavalier for the second time in the cars life. I'm not sure if a failing battery would cause this issue though.
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Old 08-09-2008, 11:36 AM DvBoard is offline  
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Perc
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The battery is fine. Like I said, the car started fine but misfired slightly for the first 10-15 seconds after startup. I then turned the radio on, and heard a loud whine that sounded like it followed the engien revs. Turned the radio back off, and then on agan and now i'm stuck with this.

The car runs fine, however. No idiot lights, no misfires, no nothing. Everything works perfectly. Guess something fried the radio.
Old 08-09-2008, 11:45 AM Perc is offline  
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dbu8554
 
No need to be a dick dude I didnt read the last part about it happening with the car is also off, and guess whats changed between radio's from 78 and 98 not much they had supressors back then they kept your engine electrical system from interfering with the radio but they sucked and went bad quickly guess what? your car has one also. anyways enough of that, as far the just the poping when you turn it up and down I had the same problem on a 98 corolla it was a improper ground+ a speaker wire was rubbing against the frame. so maybe ya wanna check that shit out.
Old 08-09-2008, 11:45 AM dbu8554 is offline  
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No need to be a dick dude I didnt read



oh genmay
Old 08-09-2008, 12:04 PM T.S.Sephiroth is offline  
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kstokes
 
You have a grounding issue somewhere. Either a bolt has backed off, a wire has been torn, or something is just somehow making a poor connection. Either the amp or the head unit has a poor connection to the chassis of the car.

If the amp and the head unit don't both have the same 0v reference voltage, you will get interesting tidbits like that happening.

The two antenna leads - Volvos use a "diversity" antenna setup. There are two antennas in the car, typically one in the rear windshield (looks like part of the heater element) and the other, a normal car antenna. The head unit compares the signal quality from both and will use whichever is receiving a better signal at the time.
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Old 08-10-2008, 03:06 AM kstokes is offline  
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Perc
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I fixed it, but I still don't know exactly what the problem was.

The amp is under the passenger seat, bolted straight to the body, so I don't think it was a grouding issue there. I did however unbolt it and re-seat all the wires, and I guess one of them wasn't really making proper contact because the problem disappared completely.

The misfire yesterday had to have been an unlucky coincidence. I guess it's time for a new rotor/distributor cap and a set of ignition leads too.

I don't have a "normal" antenna on my car by the way. I did look at the heater elements last week while washing the car, and I noticed a longer wire that runs along the bottom and left edge of the rear window. Guess that's one antenna. The other one has to be the couple of additional wires in the rear side window. (wagon).
Old 08-10-2008, 03:32 AM Perc is offline  
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I fixed it, but I still don't know exactly what the problem was.

The amp is under the passenger seat, bolted straight to the body, so I don't think it was a grouding issue there. I did however unbolt it and re-seat all the wires, and I guess one of them wasn't really making proper contact because the problem disappared completely.

The misfire yesterday had to have been an unlucky coincidence. I guess it's time for a new rotor/distributor cap and a set of ignition leads too.

I don't have a "normal" antenna on my car by the way. I did look at the heater elements last week while washing the car, and I noticed a longer wire that runs along the bottom and left edge of the rear window. Guess that's one antenna. The other one has to be the couple of additional wires in the rear side window. (wagon).

the amp doesn't ground through the case. ever. the fact that it's bolted to the body has nothing to do with the amp's ground.

this was a ground issue, and your finaggling with it obviously fixed it.
Old 08-10-2008, 09:55 PM Rang3find3r is offline  
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Perc
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Originally Posted by Rang3find3r View Post
the amp doesn't ground through the case. ever. the fact that it's bolted to the body has nothing to do with the amp's ground.

this was a ground issue, and your finaggling with it obviously fixed it.

Yeah, I guess. I just thought the misfire had something to do with it (alternator fucked, whatnot) but I guess it was an unlucky coincidence.
Old 08-11-2008, 06:59 AM Perc is offline  
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