Help needed - what's the issue? (NAD T757 static noise)

[narenvaidee]

Can someone tell me what this noise is? It was working fine, and just last week, when switched on, this noise comes up in all channels, irrespective of the volume level (i.e. doesn't increase or decrease with volume changes). Worth giving this for repairs?

Link to video -

Thanks for your inputs!

 

[Gadget Freak]

Can someone tell me what this noise is? It was working fine, and just last week, when switched on, this noise comes up in all channels, irrespective of the volume level (i.e. doesn't increase or decrease with volume changes). Worth giving this for repairs?

Link to video -

Thanks for your inputs!

Sounds like a Ground noise to me. Please check your input cables. Plug all the input signal cables and check. This will rule out where the problem is.

 

[narenvaidee]

To rule out the inputs, I disconnected everything to rule out input source noise. The one that you see in the video is just with the speaker and power chord connected. NO input source.

 

[mbhangui]

Is the noise coming on the headphone out too?
1. Doesn't look like a problem in the pre-amp, amp section. All the channels cannot go bad at the same time.
2. Power supply is common to all the channels. Could be the filter capacitor gone bad.

Is it in warranty?

 

[Blanqui]

I have the same unit with the same problem! Did you fix it?

 

[Chulbulee]

This is the "Hum" noise, coming from the power supply. The filter section (one of the two capacitors on either side of resistor/choke) has leaked/failed. To confirm try using a different one, no matter if it is a few volts up/down at output, as you would test for few seconds

 

[Blanqui]

Thanks for answering, Chulbulee. But I don't think it's one of the filters since you can hear no audio, only this noise. And when you rise the volume, you can hear "clicks" on top of that noise. It seems to me as if we were listening to the system clock or data bus.
I think volume control IC has failed. Can anyone confirm?

 

[Chulbulee]

No need of an audio. this hum penetrates everything. First clear this hurdle, then think of the clicks.

 

[efernand1]

If the above issue is related to Ground Loop, this article should help:

Ground Loops - Eliminating System Hum and Buzz

Got an annoying hum or buzz in your audio system? You likely have a ground loop. This article helps you diagnose the problem so it can be eliminated. Don't put up with hum. Read this article!

www.audioholics.com

 

[Harpreet1104]

If the above issue is related to Ground Loop, this article should help:

Ground Loops - Eliminating System Hum and Buzz

Got an annoying hum or buzz in your audio system? You likely have a ground loop. This article helps you diagnose the problem so it can be eliminated. Don't put up with hum. Read this article!

www.audioholics.com

I have same problem.....& In my case switching off the fridge resolve the issue (hum/distortion), don't know if fridge is causing problems or other

 

[Blanqui]

Chulbulee, I don't want to seem rude, but I think the noise is somewhat "digital". Can you notice the high Hz on it? It's not a recording fault, in fact, this high pitch noise is there!
No ground loops here, the noise is there with the receiver all alone.

 

[Chulbulee]

Chulbulee, I don't want to seem rude,

We are trying to find a solution ... not to get offended.

If not inconvenient, try at a different location ... some other house. See if the problem stays

 

[mbhangui]

Chulbulee, I don't want to seem rude, but I think the noise is somewhat "digital". Can you notice the high Hz on it? It's not a recording fault, in fact, this high pitch noise is there!
No ground loops here, the noise is there with the receiver all alone.

Yes. It seems like some component is oscillating. There are at least two frequencies being heard and both sound like sine waves. One is clearly above 50 Hz (motor boat kind of sound) and another close to 50 Hz (the hum kind of sound).

 

[Blanqui]

Tried it on 2 different houses. The problem persists. I can't seem to find the service manual for this device so I'm kind of lost. I'd like to know wich IC is the input selector and which one controls the volume but there are lots of them around.
Mbhangui got my point, not bad grounding nor ripple noise. Something is oscillating there and I guess it's a data bus being mixed on the audio path.