Electric humm

[Boobie Trap]

OK all you electric wizards here is one for ya!

I have a Monterey 302CR. It has three batteries. It has a battery switch for the Starboard, Port, Genset. It also has a switch to parallel the Starboard and Port engines. With that said:

When the shore electric lines are connected to the boat, battery switches turned on for the engines, radio turned on, I get a hum in the speakers. If I turn the parallel switch on, the hum drops off dramatically! Shore power disconnected, no hum! I also noticed that if I turn the cabin lights on, the hum is directly proportional to the amount of lights I turn on. Meaning that the hum grows louder.

Is there are grounding problem or a short and where could it be?
How would I track it down?

Thanks

 

[mark1905]

Re: Electric humm

I take it that you're not using an external stereo amplifier but using the internal amp on the stereo head unit? It's most likely a grounding problem. Try connecting the deck directly to a battery and see what happens. I'll bet you anything that it clears up.

 

[Boobie Trap]

Re: Electric humm

I take it that you're not using an external stereo amplifier but using the internal amp on the stereo head unit? It's most likely a grounding problem. Try connecting the deck directly to a battery and see what happens. I'll bet you anything that it clears up.

Mark1905,

Not sure I understand just what you are saying. Your talking to a true amateur!
What do you mean by external Stereo amp verses internal amp on the stereo head.? It is a Alpine amp that is in the bowels of the boat. It was installed when I got it.
Sound is fantastic except for that hum. Does not do it out of the slip so it is a minor problem. Just not right and trying to fix it.

Thanks

 

[Bob_VT]

Re: Electric humm

As I dip into my electronics hobby background.......... you are getting a high frequency hum

As a possible solution you could try some Ferrite Core 1/2" Cord Noise Suppressors on your AC shore power line.

Many laptop power supplies have them and many people do not notice or even know what they are. Go ahead and google it!!

 

[mark1905]

Re: Electric humm

AH HA.. yes.. then you are using an external amplifier. What I meant was whether or not you were connecting the speakers directly to the stereo or had an amplifier like that Alpine.

In any case, it sounds like a grounding problem as 85% of these types of issues are. Power takes the path of least resistance.. and when you have resistance in the power cables.. it will pass through your RCA cables (the round cables that only carry sound between your stereo and amplifier) and create noise. Especially when things used to be fine and then noise came with time.. that's usually corroded wire and/or fittings.

The fix for this is to make sure that all of your power connections for that amp are perfect, clean and as direct to the power source as possible. If non marine grade power cable was used, it needs to be replaced for marine grade as the soft copper that is used for standard audio power wire will corrode with time on a boat even if it's not in salt water and that could be your problem as well.

The thing with stereo amplifiers is that they have to fed good, clean, sufficient power or else they get very finicky and can even burn themselves and/or your speakers up. I've seen speakers literally pop and melt not from over power, but because the amplifier didn't have a clean source of power which made it put out a distorted sound and literally fry the speaker because of it.


Then again.. this may not be the case at all.. but it's worth it to check out.

 

[TerryMSU]

Re: Electric humm

As I dip into my electronics hobby background.......... you are getting a high frequency hum

As a possible solution you could try some Ferrite Core 1/2" Cord Noise Suppressors on your AC shore power line.

Many laptop power supplies have them and many people do not notice or even know what they are. Go ahead and google it!!

More likely this is a 60Hz hum. Not a high frequency humm at all. The noise suppressor will not hurt, but I doubt it will help. As Mark says, this is likely a grounding issue.

TerryMSU

 

[Silvertip]

Re: Electric humm

Since the problem happens when connected to shore power, I'm guessing this is charger noise. Most of the modern chargers are switcher type supplies. To illustrate this, my model airplane hauler trailer has a deep cycle battery in it for lights and powering an RC battery charger. That trailer sits in the third stall of my garage. To keep that deep cycle charged I have a 6 amp smart charger that is plugged in 24x7 although it sits at the maintanance rate most of the time. When I get into my car, that charger creates a racket on the car radio until I get out of the garage. It is not 60 cycle hum but it is a trashy charger no less. It certainly can be a grounding issue as was pointed out but it may also be a "noisy" charger.