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I have a Point 5 Subwoofer. It is connected to Yamah Rx-V420 using RCA Input as shown in Diagram 1 of the Manual. Mode switch is in SIB Position.

Presently, even after switching off the Amp, the Sub generates a humming sound, even while Bass Level and Bass Range are set at their lowest.  

I have tried setting the A/V Mode to both A and V position. Normally it is in A position.

If I remove the RCA connector then the humming sound stops.

Does my Sub need some repair. Are ther any service centres in India and particularly in the city of Pune or Mumbai.

Thanks. 

Namaste, have you tried using a different rca cable?  Perhaps that cable's ground isn't properly terminated creating some grounding noise.  If that doesnt work if your receiver or amp uses a ground on its power cable maybe use a three to two prong adapter see if that eliminates the hum.

Thanks. I did tried as per your suggestion. In the attempt, I discovered that there seems to be some problem with my Yamah RX-V420 Amp. Even while it is in standby mode, if I connect the sub to any speaker out ( which I did accidentally ), the sub gets the speaker signals and I can hear the sound clearly buy in very low volume. Probably it must be giving signals to sub too. I have not checked what happens if the Amp is actually switched off and not in stand by mode. For the time being I feel I need to take a look at the Amp. Am I likely to be correct.

 Thank you once again

Sounds like you narrowed down the suspect, tell us if you figure out anything further.

Now I am trying to find out expert for Yamah, in Pune - India. May by next week I should be able to do something

Bahut accha

It's not your amp. You have a ground loop problem. Go to a electronics specialty store and buy a ground loop isolator ($5) and attach it between the rca cable and the sub input. alternatively, you can test for this problem by taking some wire and while you hear the low humming noise, stick one end of the wire at the contact point between the rca cable and the subwoofer input jack. and the other end on a piece of metal that is attached to your home (i.e. properly grounded). if the noise goes away, then you know it's a grounding problem. If you can't find a grounding point on your home, you can try to insert the other end of the wire into the third bottom prong of your eletrical outlet, but be careful!!! make sure you are inserting it into the third ground wire prong or you're gonna electrocute yourself.

Thanks a lot. I tried it as per my understanding. Pl correct me if necessary. I have a proper grounding in all electrical sockets at home. I prepared a plug which had only one wire to the earthing. I connected one end of wire to the outer ring of the RCA Cable and another to the earthing. It did not stop the sound, but it did change. Have I done it correctly. Am I supposed to connect it to the centre pin of the RCA Cable.

So far I could not locate a shop in Pune India for the Ground Loop Isolator.

Then I tried by disconnecting the input cable. When I increase the volume controls at the Sub, it does give humming sound when there is not output. At low levels it does not. Probably it is too low to be noticed. Is it expected to generate such a sound or has my Sub developed some fault.

Hi. Yes, you connect it to the outer ring of the rca cable. If you're experiencing noise even when you're RCA cable is not connected to your sub, then i'm afraid you have a problem with the sub as now there is nothing linking the sub to the amplifier/receiver, if i understand what you have done correctly. I.e. it can't be your amplifier if your sub is making humming noise when it's not even connected to the amp/receiver. Might want to take it back for a warranty. But one more thing you might want to check is make sure you're sub is not placed beside anything metal or a magnet. Because a magnet will definately cause problems with the coils in the speaker. Sorry I can't help more than that.