Pulsing from sub

[psychofox]

Hi guys,

I have a pulsing sound from my sub, if I turn down the stereo, the pulsing nearly shakes the car. :bang:

Anyone have any ideas what this is from and how I can fix?
I have checked the earth wire, and that seems ok, the amp is getting power (light is on).

 

[volxstu]

Sounds like power coming through the RCA. Can you use a multi meter to check.

 

[psychofox]

Sounds like power coming through the RCA. Can you use a multi meter to check.

no, i dont have one.

 

[psychofox]

Sounds like power coming through the RCA. Can you use a multi meter to check.

By RCA you mean the phonos leads right?

 

[volxstu]

Yeah. I would get it sorted soon as power going through the RCA's from the Amp will blow up your HU if the issue isnt addressed.

 

[psychofox]

Yeah. I would get it sorted soon as power going through the RCA's from the Amp will blow up your HU if the issue isnt addressed.

Any idea how it happened?
Should i change the RCA's?

 

[volxstu]

Hmm actually it could be the other way round. What HU do you have? I cant remember exactly what happens unless it is a problem with a blown earth track in the HU.
This is a simple fix by just earthing the RCA Barrels but its normally quite high end HU's that this happens too. Its a defense mechanism against power being sent through the RCA's and blowing up the HU.

 

[psychofox]

Hmm actually it could be the other way round. What HU do you have? I cant remember exactly what happens unless it is a problem with a blown earth track in the HU.
This is a simple fix by just earthing the RCA Barrels but its normally quite high end HU's that this happens too. Its a defense mechanism against power being sent through the RCA's and blowing up the HU.

Its this one
http://docs.pioneer.eu/Manuals/DEH_2820MP_URD3873_manual/

Pioneer DEH-2820MP

 

[volxstu]

OK well im not 100% sure if your unit has it but it does sound like a blown earth track. I have exactly the same with my pioneer unit. It mainly happens if you plug the RCA's into the amp without the Earth wire connected.
Does this sound like a possibility?

 

[psychofox]

OK well im not 100% sure if your unit has it but it does sound like a blown earth track. I have exactly the same with my pioneer unit. It mainly happens if you plug the RCA's into the amp without the Earth wire connected.
Does this sound like a possibility?

Honesty, no.
I have had this set up for over 2 years, i havent touched or changed a thing.
One day it started pulsing about 30 min after i had turned it on.

 

[volxstu]

OK well i just need to get a couple of things confirmed, i would hate to tell you do the wrong thing. People have thrown away perfectly serviceable head units over this kind of problem.
It does sound like your amp is trying to earth through the RCA's which will just mean earthing the RCA's.

 

[psychofox]

OK well i just need to get a couple of things confirmed, i would hate to tell you do the wrong thing. People have thrown away perfectly serviceable head units over this kind of problem.
It does sound like your amp is trying to earth through the RCA's which will just mean earthing the RCA's.

mate, whatever help you give if much appreciated.
How would I go about earthing the RCA's?

 

[volxstu]

solder a piece of wire to the barrell to the rca barrel and splice into the hu's earth

 

[psychofox]

solder a piece of wire to the barrell to the rca barrel and splice into the hu's earth

erm
:bang: no access to solder, and i wouldnt have a clue how to do this.
Damn it.

Any idea how this would have happened?

 

[volxstu]

I spose if nothing has changed or been removed in the last 2 years then its just one of those things lol.
If you really cant get hold of a soldiering iron then you could strip enough thick cable like a stiff blue remote wire and then wrap that with a lot of electrical tape. I would do it at the HU end and amp end.

 

[psychofox]

ok, thanks, i'm going to take another look at it tomorrow.

 

[psychofox]

Thinking about it, my boot got wet during the last big freeze we had. Im guessing some water got into the seal of the roof/boot, froze, then melted - dripping into the boot. It was near the area of the sub (not the amp).
Would this have anything to do with it? I checked the sub, the carpet was dampish, but I doubt anything got inside. I waited for the whole boot to dry out before I turned anything on, it worked fine for about 30 min (as above).

 

[volxstu]

It could have caused it i would imagine. Is it particularly expensive amp, if not then i would just put it down to age.

 

[psychofox]

It could have caused it i would imagine. Is it particularly expensive amp, if not then i would just put it down to age.

Not really, bought it from ebay afew years ago.
The puzzling part is, the amp never got wet.

 

[volxstu]

Damp in the air though.