speaker volume cuts way down when i touch amp

TuroK27 · 16th August 2006, 03:31 AM

ok so i hooked it up earlier todayago & all 4 channels apparently work, buuuuttt...for some reason when i put my hand on the amp heatsink the sound cut out(like it muted)& suddenly some smoke was coming from my headunit & rca wires had gotten very warm all the way from the amp to the head unit. the head unit is ok after all that & i hooked up a speaker to all 4 channels of the car amp one at a time & for some reason the sound cut out every time i touched the heatsink. of course i would cut power to the stereo after every time the sound muted on me as i didnt want to burn something up permanently. i just hope my headunit wont malfunction on me now.dont know if i trust it now that i saw & smelled smoke coming from it.

ifrythings · 16th August 2006, 06:14 AM

Sounds like you have a grounding issuse with your amplifier?

Check all your power connections and if none are wong you may have a bad ground connection in your amp.

If you have a bad ground connection in your amp, the amp will use the rca wire grounds as a return point for the heavy current.(heavy current through rca cable =

)

If I were you, I'd pull your deck out and take a look at the bottom of the circuit board for a burn't trace

BTW when you put your hand on the amp, thats probly when the bad connection appears.

Perry Babin · 16th August 2006, 06:28 AM

There's too much current flowing through the RCA cables (as was mentioned in a previous post). It's normal for some amps to pass a small current (a few milliamps) through the RCA shields but it should NEVER heat the RCA cables.

Do not connect the amp to the head unit again until it's been check by a repair tech.

There are at least two possible reasons for this to happen.

If the amp was not properly grounded, there are a few amps that can try to ground through the RCA shields. Some amplifier must have previous damage to do this. Others will do it if they're in proper working order (something the manufacturer changed).

If the transformer shorted (primary windings shorted to secondary windings), the B+ supply can pass to the RCAs on some amps.

Either will damage a head unit.

You can check the shield ground of the head unit with an ohm meter. Unplug the RCA cables from the head unit. Set your meter to ohms. Touch the black lead to the case of the head unit. Touch the red lead to the outer shield ground connection of the head unit's RCA jacks. You should read no more than 2 or 3 ohms. Ideally, you'll read 0 ohms. If you have an open connection, the head unit is damaged.

TuroK27 · 17th August 2006, 06:25 AM

thanks everyone,
ill have to do some troubleshooting now that i have some sense of direction. the head unit seems fine so far. i hooked it up to another amp(one that works) & it still works....for how long who knows but i have no confidence in it. twice ive had smoke come out of that headunit, figured something would be bad by now or bout ready to be.
thanks again guys

16th August 2006, 03:31 AM	#1
TuroK27 diyAudio Member Join Date: May 2005 Location: Indiana	speaker volume cuts way down when i touch amp ok so i hooked it up earlier todayago & all 4 channels apparently work, buuuuttt...for some reason when i put my hand on the amp heatsink the sound cut out(like it muted)& suddenly some smoke was coming from my headunit & rca wires had gotten very warm all the way from the amp to the head unit. the head unit is ok after all that & i hooked up a speaker to all 4 channels of the car amp one at a time & for some reason the sound cut out every time i touched the heatsink. of course i would cut power to the stereo after every time the sound muted on me as i didnt want to burn something up permanently. i just hope my headunit wont malfunction on me now.dont know if i trust it now that i saw & smelled smoke coming from it.

16th August 2006, 06:28 AM	#3
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	There's too much current flowing through the RCA cables (as was mentioned in a previous post). It's normal for some amps to pass a small current (a few milliamps) through the RCA shields but it should NEVER heat the RCA cables. Do not connect the amp to the head unit again until it's been check by a repair tech. There are at least two possible reasons for this to happen. If the amp was not properly grounded, there are a few amps that can try to ground through the RCA shields. Some amplifier must have previous damage to do this. Others will do it if they're in proper working order (something the manufacturer changed). If the transformer shorted (primary windings shorted to secondary windings), the B+ supply can pass to the RCAs on some amps. Either will damage a head unit. You can check the shield ground of the head unit with an ohm meter. Unplug the RCA cables from the head unit. Set your meter to ohms. Touch the black lead to the case of the head unit. Touch the red lead to the outer shield ground connection of the head unit's RCA jacks. You should read no more than 2 or 3 ohms. Ideally, you'll read 0 ohms. If you have an open connection, the head unit is damaged. __________________ Links >> Basic Car Audio Amp Repair --- Basic Car Audio Electronics --- Basic Transistor Testing --- Basic Switching Power Supply Design --- Basic Computer Skills << Links

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16th August 2006, 06:14 AM	#2
ifrythings diyAudio Member Join Date: Oct 2005	Sounds like you have a grounding issuse with your amplifier? Check all your power connections and if none are wong you may have a bad ground connection in your amp. If you have a bad ground connection in your amp, the amp will use the rca wire grounds as a return point for the heavy current.(heavy current through rca cable = ) If I were you, I'd pull your deck out and take a look at the bottom of the circuit board for a burn't trace BTW when you put your hand on the amp, thats probly when the bad connection appears.

17th August 2006, 06:25 AM	#4
TuroK27 diyAudio Member Join Date: May 2005 Location: Indiana	thanks everyone, ill have to do some troubleshooting now that i have some sense of direction. the head unit seems fine so far. i hooked it up to another amp(one that works) & it still works....for how long who knows but i have no confidence in it. twice ive had smoke come out of that headunit, figured something would be bad by now or bout ready to be. thanks again guys

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