problems.. dunno what it is

Staticjeep · 9th September 2005, 08:17 PM

hello, an amp i bought about 6 months ago has started screwing up. well i though it was the amp.. so i got it replaced for free. last night after i got it installed and everything the same problem happened again. so now im thinkin its not my amp. the problem im having is when i turn the gain up or the bass boost the subs just start thumping out of no where even if i turn the volume all the way down on the cd player. i think its somewhere in my wires or my headunit. ive tryed replacing my RCA cables but i dont think thats it. one thing that comes to mind is the ground. because when i open the door or something/turn on the light i head a thump and well. i check all my ground and everything seems fine.. although there could be a ground messed up on my cd player. i think all my speakers would thump tho. i dont know.. any help will be appreciated.

sr20dem0n · 9th September 2005, 08:24 PM

Does it still make those thumps when the rcas are unplugged from the amp completely? If so then check the amp's ground closer, make sure the paint is shaved off of the point you're grounding it, make sure it's solid, etc. If it stops thumping when you unplug the rcas then check your headunit ground, if you're using the stock ground in the harness it might have come loose or maybe it was just bad in the first place, it's always a good idea to run your own ground to one of the bolts in the dash.

Staticjeep · 9th September 2005, 08:28 PM

no it doesnt thump when i unplug the rcas.. when i plug in my mp3 player to the rcas everything is normal... i will check my cd player ground as soon as my mom comes home from work.. she took my car today because hers is in the shop

Perry Babin · 10th September 2005, 12:09 AM

It could be an open shield ground on the head unit's RCA outputs.

Unplug the RCAs from the head unit and use an ohm meter to measure the resistance from the case of the head unit to the shield of the RCA outputs. The resistance should be very close to zero ohms. If it reads open, the shield ground is burned open or has a bad solder connection.

xplod1236 · 10th September 2005, 01:03 AM

Are you running your signal cables next to the power wire?

Staticjeep · 10th September 2005, 02:14 PM

I think ive found the problem, my rcas and my antenna. when i let the 2 touch it works perfectly. i dont know what the hell is wrong with them or which one needs some metal or something. but when i connect them 2 it works fine.. for right now ive used some electrical tape and taped them together and for right now its working fine. although i thinks its something in my headunit thats messed up. i dunno what the ground shield is but that could be it.. any more info appreciated.

Perry Babin · 11th September 2005, 11:43 PM

If touching the outer shield of the antenna to the RCA shield allows the system to work properly, it's means that the shield ground is open.

Inside the head unit, the RCA shield (the outer metallic conductor) is connected to the audio ground (which is connected to the case of the head unit in most all head units). When a power source is allowed to contact the shield of the RCAs anywhere in the system (even where the amps are located), the copper foil traces on the circuit board are burned. When this happens, the connection between the audio ground and the RCA shield ground is opened and you will have all sorts of problems (EXCESSIVE engine noise is the most common symptom).

To properly repair it, you would have to repair the open trace in the head unit. This is best left to a qualified tech. To get the unit to operate properly until you can have it properly repaired, you can solder a wire across the two RCA cable shields (the outer metallic part). Then ground the wire to the case of the head unit.

Since the RCA cables have likely contacted some power source, it could happen again. Since the fusible trace is no longer a part of the circuit, you should insert a 1 amp fuse in the wire that you connect between the shield and the case of the head unit. This will prevent excessive current flow in the RCA shields if it happens again.

To prevent this from happening again, you need to be sure that you remove the main power fuse when working on the system. If the RCAs are a set that are no longer being used, unplug them from the head unit. If they are unplugged from an amp (because the amp is being removed for a short time), insulate the RCAs so that they can not short to any power source.

There is at least one other way that power can be applied to the RCAs even if your system is perfectly installed and everything is properly insulated. In some amplifiers, the secondary ground is left floating (not connected to chassis ground). If the transformer shorts (primary to secondary inside the amplifier), the battery supply voltage will be connected/shorted to the secondary ground and then to the RCA shield ground. In this situation, the amplifier MUST be serviced by a qualified technician.

Zimo · 12th September 2005, 01:03 AM

Hey!

Im just curious because this case seems just like one of my friend´s half a year ago. Is your player Pioneer? Well my friend have a Pioneer MP3 player and he had somehow destroyed it when removing RCA cables from his amp. The signs of your problem fits just like a glove to his.
I helped him to fix his player when we decided it is the one which causes the problem. And I can confirm that there are two "fuses" made of the foil which ends up to RCA connectors. You will be able to see that these two fuses have "blown"

So if you have same player of similar to my friend´s one, there are also four solder areas to passing by these fuses (have to thank Pioneer of this

). So I just connected those with solder and checked that connections work with a multimeter.

It worked fine then. But indeed like Perry Babin said this kind of solution makes the player more vulnerable to getting it broked. So I also think it would be a good idea to readd those fuses somehow..

Or just to be more careful

Staticjeep · 12th September 2005, 02:08 AM

yes, my player is an pioneer, actually its a Pioneer DEH-P4700MP. and ive figured out the problem, somehow the rcas are not grounded, my antenna acts like an ground when i touch the rcas with the antenna. i will go to circuitcity and see what they say, ill explain the situation to them and everything. i have an 2 year warranty on it so i can just get it replace or fixed... anyway thanks for your advice... im sure i would follow it if i didnt have the warranty

DigitalJunkie · 12th September 2005, 04:33 AM

Almost sounds like a bad ground on the headunit.

The outer shield of the antenna cable is grounded.If it works with the antenna plugged in,and doesn't work with it unplugged,there's a grounding issue.

9th September 2005, 08:17 PM	#1
Staticjeep diyAudio Member Join Date: Jun 2005 Location: Florida	problems.. dunno what it is hello, an amp i bought about 6 months ago has started screwing up. well i though it was the amp.. so i got it replaced for free. last night after i got it installed and everything the same problem happened again. so now im thinkin its not my amp. the problem im having is when i turn the gain up or the bass boost the subs just start thumping out of no where even if i turn the volume all the way down on the cd player. i think its somewhere in my wires or my headunit. ive tryed replacing my RCA cables but i dont think thats it. one thing that comes to mind is the ground. because when i open the door or something/turn on the light i head a thump and well. i check all my ground and everything seems fine.. although there could be a ground messed up on my cd player. i think all my speakers would thump tho. i dont know.. any help will be appreciated.

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9th September 2005, 08:24 PM	#2
sr20dem0n diyAudio Member Join Date: Apr 2005 Location: Broomfield, CO	Does it still make those thumps when the rcas are unplugged from the amp completely? If so then check the amp's ground closer, make sure the paint is shaved off of the point you're grounding it, make sure it's solid, etc. If it stops thumping when you unplug the rcas then check your headunit ground, if you're using the stock ground in the harness it might have come loose or maybe it was just bad in the first place, it's always a good idea to run your own ground to one of the bolts in the dash.

9th September 2005, 08:28 PM	#3
Staticjeep diyAudio Member Join Date: Jun 2005 Location: Florida	no it doesnt thump when i unplug the rcas.. when i plug in my mp3 player to the rcas everything is normal... i will check my cd player ground as soon as my mom comes home from work.. she took my car today because hers is in the shop

10th September 2005, 12:09 AM	#4
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	It could be an open shield ground on the head unit's RCA outputs. Unplug the RCAs from the head unit and use an ohm meter to measure the resistance from the case of the head unit to the shield of the RCA outputs. The resistance should be very close to zero ohms. If it reads open, the shield ground is burned open or has a bad solder connection.

10th September 2005, 01:03 AM	#5
xplod1236 diyAudio Member Join Date: Dec 2003 Location: On the couch	Are you running your signal cables next to the power wire?

10th September 2005, 02:14 PM	#6
Staticjeep diyAudio Member Join Date: Jun 2005 Location: Florida	I think ive found the problem, my rcas and my antenna. when i let the 2 touch it works perfectly. i dont know what the hell is wrong with them or which one needs some metal or something. but when i connect them 2 it works fine.. for right now ive used some electrical tape and taped them together and for right now its working fine. although i thinks its something in my headunit thats messed up. i dunno what the ground shield is but that could be it.. any more info appreciated.

11th September 2005, 11:43 PM	#7
Perry Babin diyAudio Member Join Date: Nov 2003 Location: Louisiana	If touching the outer shield of the antenna to the RCA shield allows the system to work properly, it's means that the shield ground is open. Inside the head unit, the RCA shield (the outer metallic conductor) is connected to the audio ground (which is connected to the case of the head unit in most all head units). When a power source is allowed to contact the shield of the RCAs anywhere in the system (even where the amps are located), the copper foil traces on the circuit board are burned. When this happens, the connection between the audio ground and the RCA shield ground is opened and you will have all sorts of problems (EXCESSIVE engine noise is the most common symptom). To properly repair it, you would have to repair the open trace in the head unit. This is best left to a qualified tech. To get the unit to operate properly until you can have it properly repaired, you can solder a wire across the two RCA cable shields (the outer metallic part). Then ground the wire to the case of the head unit. Since the RCA cables have likely contacted some power source, it could happen again. Since the fusible trace is no longer a part of the circuit, you should insert a 1 amp fuse in the wire that you connect between the shield and the case of the head unit. This will prevent excessive current flow in the RCA shields if it happens again. To prevent this from happening again, you need to be sure that you remove the main power fuse when working on the system. If the RCAs are a set that are no longer being used, unplug them from the head unit. If they are unplugged from an amp (because the amp is being removed for a short time), insulate the RCAs so that they can not short to any power source. There is at least one other way that power can be applied to the RCAs even if your system is perfectly installed and everything is properly insulated. In some amplifiers, the secondary ground is left floating (not connected to chassis ground). If the transformer shorts (primary to secondary inside the amplifier), the battery supply voltage will be connected/shorted to the secondary ground and then to the RCA shield ground. In this situation, the amplifier MUST be serviced by a qualified technician.

12th September 2005, 01:03 AM	#8
Zimo diyAudio Member Join Date: Oct 2004	Hey! Im just curious because this case seems just like one of my friend´s half a year ago. Is your player Pioneer? Well my friend have a Pioneer MP3 player and he had somehow destroyed it when removing RCA cables from his amp. The signs of your problem fits just like a glove to his. I helped him to fix his player when we decided it is the one which causes the problem. And I can confirm that there are two "fuses" made of the foil which ends up to RCA connectors. You will be able to see that these two fuses have "blown" So if you have same player of similar to my friend´s one, there are also four solder areas to passing by these fuses (have to thank Pioneer of this ). So I just connected those with solder and checked that connections work with a multimeter. It worked fine then. But indeed like Perry Babin said this kind of solution makes the player more vulnerable to getting it broked. So I also think it would be a good idea to readd those fuses somehow.. Or just to be more careful

12th September 2005, 02:08 AM	#9
Staticjeep diyAudio Member Join Date: Jun 2005 Location: Florida	yes, my player is an pioneer, actually its a Pioneer DEH-P4700MP. and ive figured out the problem, somehow the rcas are not grounded, my antenna acts like an ground when i touch the rcas with the antenna. i will go to circuitcity and see what they say, ill explain the situation to them and everything. i have an 2 year warranty on it so i can just get it replace or fixed... anyway thanks for your advice... im sure i would follow it if i didnt have the warranty

12th September 2005, 04:33 AM	#10
DigitalJunkie diyAudio Member Join Date: Apr 2003 Location: Portland,Oregon Blog Entries: 3	Almost sounds like a bad ground on the headunit. The outer shield of the antenna cable is grounded.If it works with the antenna plugged in,and doesn't work with it unplugged,there's a grounding issue.

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