Promblem with noise?

[suspencefull]

I have tried everything to figure out the source of a noise problem. I had tried everything. Even directly connected the amp and hu to the battery. No matter what if the car is on (alternator running) I got noise in the speakers. I thought it was a bad alternator. I got a new one put in and I still have the problem. any help would be awesome. Thanks.

-Jeff

[Perry Babin]

If the noise is REALLY bad, you likely have an open shield ground on the head unit.

To check it...

Unplug all RCA cables from the head unit
multimeter on ohms
One meter lead on the case of the head unit
The other lead on the shield of the RCA output jacks of the head unit

You should read approximately the same as when you touch the meter leads together (~0 ohms). If you read more than a few ohms, you likely have an open shield ground. If it's more than 10 ohms, have the head unit checked out by a tech.

A simple test is to connect the shield of the RCAs to the case of the head unit (when the RCAs are connected as usual). You need to make the connection with the system off. If you do it while it's on, it could result in a loud pop which could damage your speakers. If the noise goes away with the jumper in place, the shield connection is open inside the head unit.

[suspencefull]

Going to try that right now. Let you know how it goes.

[suspencefull]

You are a miracle worker. I've worked hours trying to figure out what was wrong. The weird thing is that I had tried a different head unit and it had the same noise problem. It was before I got the new alternator installed (Don't know if that mattered.). Also, it only had the problem when the engine was running, but thatnks a lot.

On the ohm meter, I was getting readings int he Mega Ohms. I was going to try a different meter tommorrow.

Is there anyway to reattach the ground or permenately attach the case to the ground? Or is this not safe? I would rather not have to get a new head unit.

[Perry Babin]

If you have two head units with the same problem, you don't want to leave that jumper in place. It could create a fire hazard.

Until you can get it properly repaired, you can use a jumper but it needs to be fused with nothing larger than a 3 amp fuse. If the fuse blows, you either have a defective amplifier or you're allowing a 12 volt power source to contact the shield ground. Do NOT use anything larger than a 3 amp fuse.

[suspencefull]

Will do? Does it matter whether it is a slow blow or fast blow fuse?

Also, is there anyway I could repair it myself? or would this not be recommended. If it is just an easy soldering or fuse replacement inside I could probably do it.

I will try to see if I can get another HU to test with. I assume the noise should go away with a new HU.

Thanks for the help.

[Perry Babin]

Use a fast-blow fuse. Under normal operating conditions, there will never be more than approximately 0.01 amps of current through the shields. If something causes more than an amp of current to flow through the shields, you want the circuit to open as quickly as possible.

The repair is generally simple but I don't know how skillful you are so I'd have to recommend against it.

I'd recommend using the head unit with the fused jumper for a week or two. If the amplifier has an intermittant problem that's causing the head unit's shield to fuse open, it would be good to find that by blowing the fuse instead of damaging another head unit.

What amplifiers are you using?

[suspencefull]

I have a soundstream Rub600-4. Then an Orion HCA-800 I believe. Right now, I only haVE THe soundstream hooked up. I will set it up like you said for a couple of weeks to see what happens.

If it is a simple repair, I can probably do it. I have repaired a bad home pre-amp that had a similar problem. The ground trace was burnt up, on the front outputs. I was getting all kinds of noise on those channels. Thanks for the help.

[excetara2]

How'd it go?

[suspencefull]

So far so good. I connected when end of 3 amp fuse to chassis of HU and other end to the grounds of all the rcas. So far so good but haven't connected Sub amp back up. Wait a couple of days first to see how this goes.