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car stereo problem (Read 1786 times)
freediver
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car stereo problem
Aug 6th, 2019 at 8:06am
 
The CD player in my car stopped working. So I picked up a cheap portable CD player from Jaycar, with a cigarette plug thing to power it. But when I power it from the car, I get an annoying pulsing whistling noise through the car speakers. I don't get it if I run the CD player on AA batteries. The noise is there even if the engine is not running, so it is not the alternator. It is 'in time' with the spindle of the CD player. If I pop the lid open on the CD player, as the CD slows down the pulsing of the noise slows down in time with the CD. I also tried another CD player of the same make/model, a different auxiliary lead, and one of those capacitor things for cancelling alternator noise. The Jaycar people were helpful, but they have run out of ideas, though they think what I have done has worked for other people.

Any tips on how to fix it? I've looked into a new car stereo and switching to some kind of USB option, but want to stick with CDs for the moment, and it is an old car so I don't want to spend heaps of money on it.
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Bobby.
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Re: car stereo problem
Reply #1 - Aug 6th, 2019 at 8:16am
 
I don't understand.
The CD player has it's own speakers.
How can they cause a noise in the car speakers?
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Re: car stereo problem
Reply #2 - Aug 6th, 2019 at 8:26am
 
I plug it into the car stereo with an auxiliary lead from the headphone jack on the portable CD player to the aux input on the stereo. Only the CD player and digital display on the stereo is broken. The rest of it works, and you can listen to the radio, though it is a bit difficult to navigate channels without the display.
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Re: car stereo problem
Reply #3 - Aug 6th, 2019 at 8:43am
 
It sounds like it is some sort of radiated or generated interference from inside the ext CD player.

Connecting the car battery supply might act as an antenna.

It is unlikely the speakers would be affected unless they were being supplied from an active amplifier.

You probably need one of those ferrite suppressors you often see on the external lead/s on various equipment

You would have to thread the 12 dc lead/s through the ferrite suppressor/s.

Place the ferrite suppressor/s on the 12V DC as close as possible to the ext CD player.

Another experiment would be to completely wrap the ext CD player in some aluminium foil which will stop RF radiation.


JAYCAR has these ferrite suppressors.

...
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Re: car stereo problem
Reply #4 - Aug 6th, 2019 at 8:46am
 
freediver wrote on Aug 6th, 2019 at 8:26am:
I plug it into the car stereo with an auxiliary lead from the headphone jack on the portable CD player to the aux input on the stereo. Only the CD player and digital display on the stereo is broken. The rest of it works, and you can listen to the radio, though it is a bit difficult to navigate channels without the display.


Hi FD,
it sounds like an earth loop problem.
The headphone output is not compatible
with the auxiliary input.
Is there another output you can use?
For the cost of trying to sort it out
it would be  cheaper to buy a 2nd hand
CD player from the car wreckers.
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Re: car stereo problem
Reply #5 - Aug 6th, 2019 at 8:47am
 
The car CD player probably has a stuck disk as this is a very common problem.

It is caused by grease from fingers on the CD getting on the friction pads which grip the CD and which start to slip when greasy and leave a CD stuck half way.

A CD player cleaning kit needs to be used once a month to remove the grease from the CD friction pads.
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« Last Edit: Aug 6th, 2019 at 9:07am by juliar »  
 
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Re: car stereo problem
Reply #6 - Aug 6th, 2019 at 8:54am
 
juliar wrote on Aug 6th, 2019 at 8:47am:
The car CD player probably has a stuck disk as this is a very common problem.

It is cause by grease from fingers on the CD getting on the friction pads which grip the CD and which start to slip when greasy and leave a CD stuck half way.

A CD player cleaning kit needs to be used once a month to remove the grease from the CD friction pads.


I assume that FD would have had a go at
fixing the car CD player?

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Re: car stereo problem
Reply #7 - Aug 6th, 2019 at 9:06am
 
Try running the CD player from a different power supply, either batteries or a power lead and see what happens
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Re: car stereo problem
Reply #8 - Aug 6th, 2019 at 9:21am
 
juliar wrote on Aug 6th, 2019 at 8:47am:
The car CD player probably has a stuck disk as this is a very common problem.

It is caused by grease from fingers on the CD getting on the friction pads which grip the CD and which start to slip when greasy and leave a CD stuck half way.

A CD player cleaning kit needs to be used once a month to remove the grease from the CD friction pads.


It has a stuck disc and several other problems. Not worth fixing.

Quote:
For the cost of trying to sort it out
it would be  cheaper to buy a 2nd hand
CD player from the car wreckers.


A lot of them have security codes etc that make things complicated. If I was going to the trouble of replacing the stereo I think I'd just buy a new one.

Quote:
Try running the CD player from a different power supply, either batteries or a power lead and see what happens


It does not happen if I run it off AA batteries.
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Re: car stereo problem
Reply #9 - Aug 6th, 2019 at 9:28am
 
You could stuff around infinitum trying to filter the cars power source. Buy some rechargeable AAs from Aldi and a charger that runs off the car.

Does the cars tape deck still work?  Smiley
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Re: car stereo problem
Reply #10 - Aug 6th, 2019 at 9:33am
 
Bobby is very likely correct and that it is an earth loop where the ext CD player is connected to earth thru the 12V cable and ALSO thru the audio connection to the car amp.

One quick trick is to cut the earth wire on the ext CD 12V DC cable and let the ext CD player earth thru the car amp.

This may not work as the car amp may have a balanced audio input which does not use an earth except for the shield around the cable.


A better solution would be to use an earth loop isolator.

...



Jaycar has several of these earth loop isolators

...



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Re: car stereo problem
Reply #11 - Aug 6th, 2019 at 12:01pm
 
The easiest way to solve this is to test it in someone else's car. If the noise is not present in another car the problem is in your car. Otherwise, the problem is in the power supply for the device.

If you establish its the device you can return it for money back or exchange for another brand.
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Re: car stereo problem
Reply #12 - Aug 6th, 2019 at 1:42pm
 
LarfTillUFart,

All that has already been done except in another car which can be quite misleading depending on the earthing involved.

It is fairly obviously an earth loop issue as with batteries in the ext CD it works OK with the ext CD audio output plugged into the car amp audio input.

A quick fix might be to disconnect the earth wire in the 12V DC power lead and use the earth through the car amp.

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Re: car stereo problem
Reply #13 - Aug 6th, 2019 at 3:14pm
 
juliar wrote on Aug 6th, 2019 at 1:42pm:
LarfTillUFart,

All that has already been done except in another car which can be quite misleading depending on the earthing involved.

It is fairly obviously an earth loop issue as with batteries in the ext CD it works OK with the ext CD audio output plugged into the car amp audio input.

A quick fix might be to disconnect the earth wire in the 12V DC power lead and use the earth through the car amp.



There is no earth in car wiring There is only positive and negative. Negative is usually connected to the chassis of the car.

In this case, the slowing down of the CD and noise suggests a high resistance of the connection in the cigarette lighter socket. A spray of electrical contact cleaner could clean this up if it is not a severe corrosion issue.

Could also be how the negative is connected, whether wired from the battery, wired from the chassis, or just metal-metal contact of the lighter socket to the car body.
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« Last Edit: Aug 6th, 2019 at 4:15pm by Laugh till you cry »  

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Re: car stereo problem
Reply #14 - Aug 6th, 2019 at 7:05pm
 
juliar wrote on Aug 6th, 2019 at 1:42pm:
LarfTillUFart,

All that has already been done except in another car which can be quite misleading depending on the earthing involved.

It is fairly obviously an earth loop issue as with batteries in the ext CD it works OK with the ext CD audio output plugged into the car amp audio input.

A quick fix might be to disconnect the earth wire in the 12V DC power lead and use the earth through the car amp.




That is one possible way of fixing it.
At least then there's only one earth.
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Re: car stereo problem
Reply #15 - Aug 6th, 2019 at 10:11pm
 
If it was an earth loop that would imply it is picking up radiated interference, but the noise seems to be coming from the portable CD player itself.

Three experiments I can try:

* another car
* wrapping electrical tape around the cigarette plug to cut the negative connection
* a ferite loop
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Re: car stereo problem
Reply #16 - Aug 6th, 2019 at 10:39pm
 
freediver wrote on Aug 6th, 2019 at 10:11pm:
If it was an earth loop that would imply it is picking up radiated interference, but the noise seems to be coming from the portable CD player itself.

Three experiments I can try:

* another car
* wrapping electrical tape around the cigarette plug to cut the negative connection
* a ferite loop



No FD,
an earth loop means that the power drawn by the CD player is in the same earth as the audio earth.
That's why it gets picked up as signal and amplified.

Cutting the negative connection on the ciggy socket might work -
it might also make it worse.

Earth loops are devilish problems and
design engineers have to go
to extreme lengths to get rid of them.
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Re: car stereo problem
Reply #17 - Aug 6th, 2019 at 10:44pm
 
Everything is earthed to the car body. I'm pretty sure an earth loop means a loop.
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Re: car stereo problem
Reply #18 - Aug 6th, 2019 at 10:47pm
 
An earth loop is indeed a loop. It depends on how many and how good the earth points are. One high resistance earth is all it takes.
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Re: car stereo problem
Reply #19 - Aug 6th, 2019 at 11:02pm
 
freediver wrote on Aug 6th, 2019 at 10:44pm:
Everything is earthed to the car body. I'm pretty sure an earth loop means a loop.



An earth loop means that there are different earths
at slightly different voltages -
they are not all at zero volts.
It doesn't matter with high power devices but
it does when you are amplifying tiny signals.
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Re: car stereo problem
Reply #20 - Aug 6th, 2019 at 11:10pm
 
That's not what it means Bobby.
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Re: car stereo problem
Reply #21 - Aug 6th, 2019 at 11:14pm
 
freediver wrote on Aug 6th, 2019 at 11:10pm:
That's not what it means Bobby.



https://en.wikipedia.org/wiki/Ground_loop_(electricity)


In an electrical system, a ground loop or earth loop occurs when two points of a circuit both intended to be at ground reference potential have a potential between them.[1] This can be caused, for example, in a signal circuit referenced to ground, if enough current is flowing in the ground to cause two points to be at different potentials.

Ground loops are a major cause of noise, hum, and interference in audio, video, and computer systems. Wiring practices that protect against ground loops include ensuring that all vulnerable signal circuits are referenced to one point as ground. The use of differential connections can provide rejections of ground-induced interference. Removal of safety ground connections to equipment in an effort to eliminate ground loops also eliminates the protection the safety ground connection is intended to provide.


...
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Re: car stereo problem
Reply #22 - Aug 6th, 2019 at 11:19pm
 
This is all Juliarshit.

There is no connection to earth in a car which sits on rubber tyres and no part of the electrical system is earthed by connection to earth.

The negative connection is just a common which is connected to the metallic body of a car.

Connections from the car body or chassis or other metal parts are not reliable because of the effect of paint or corrosion or both.
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Re: car stereo problem
Reply #23 - Aug 7th, 2019 at 6:16am
 
Laugh till you cry wrote on Aug 6th, 2019 at 11:19pm:
This is all Juliarshit.

There is no connection to earth in a car which sits on rubber tyres and no part of the electrical system is earthed by connection to earth.

The negative connection is just a common which is connected to the metallic body of a car.

Connections from the car body or chassis or other metal parts are not reliable because of the effect of paint or corrosion or both.



Zero volts in the car is referred to as earth.
There are many different earths.
If you don't understand this drawing then you shouldn't comment:

...
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Re: car stereo problem
Reply #24 - Aug 7th, 2019 at 7:06am
 
Hi FD,
could you do this please? -
plug in your headphones to the CD player & see if you can hear that motor noise while you are
using the car ciggy lighter connection for power?

cheers
Bobby
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Re: car stereo problem
Reply #25 - Aug 7th, 2019 at 8:10am
 
Are you suggesting one of the 'earths' is not actually connected to the car chassis properly? ie floating?
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Re: car stereo problem
Reply #26 - Aug 7th, 2019 at 8:24am
 
freediver wrote on Aug 7th, 2019 at 8:10am:
Are you suggesting one of the 'earths' is not actually connected to the car chassis properly? ie floating?



No - i just want to see if the noise is coming
from the CD player or if it's generated  in
a ground loop inside the car.
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Re: car stereo problem
Reply #27 - Aug 7th, 2019 at 9:36am
 
Bobby. wrote on Aug 7th, 2019 at 7:06am:
Hi FD,
could you do this please? -
plug in your headphones to the CD player & see if you can hear that motor noise while you are
using the car ciggy lighter connection for power?

cheers
Bobby


While simultaneously rollerskating and juggling?
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Re: car stereo problem
Reply #28 - Aug 7th, 2019 at 10:06am
 
LarfTillUFart really knows her stuff, doesn't she ?   Probably a Greeny.

How ignorant can she be ? The Car Body is referred to as an earth in this case as the more intelligent posters have recognized.

Small voltages between the 2 earth or -ve connections are the cause of the interference.

As the ext CD works OK when it operates off its own batteries clearly indicates an earth loop problem.

Quick solution just cut the 12v DC earth or -ve wire and let it earth thru the car amp then only one earth.

Suppose it is also possible to get interference thru the two 12v +ve connections.

Thus the best solution is an earth loop isolator from JAYCAR inserted between the ext CD audio output and the car amp audio input.

Testing in another car can be quite misleading as the earth loop could be quite different.
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« Last Edit: Aug 7th, 2019 at 1:24pm by juliar »  
 
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Re: car stereo problem
Reply #29 - Aug 7th, 2019 at 12:31pm
 
Juliar suggests: Performing the tests recommended by Bobbi while simultaneously rollerskating, juggling, nonsensically yodeling, and balancing a jug of beer on its flat cranium.
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Re: car stereo problem
Reply #30 - Aug 7th, 2019 at 1:23pm
 
LarfTillUFart is not the full quid.  Probably a loony Greeny.
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