Problem with NAD3020.Inputs not working.

[tenzz]

Hello.

I recently got from a friend an old 3020.The problem is that none of the inputs is working properly.

I actually got the amp so i can connect my pc through the aux inputs.But as long as i connect the cable the only thing that comes from the speakers is a noise (quite strong).If the cable is not connected nothing is heard.The same if i try the other inputs.

I am 100% sure that the cable delivers the signal from my pc, and 95% that my speakers are fine as they are completly new (wharefedale 9.0) just out of the box.(at least i know that they can produce a noise)

As i have limited diy knowledge and tools (a cheap soldering iron and a multimeter) i cant make any tests on my own and i dont know any reliable service around the area so i would like to ask you what is your first thought about my case.

I know that a re-cap would be very profiting for the amp and i will do it as soon as i'll find a nice service point.I would like to know if there is anything i could check or try on my own as the only thing that concerns me at the moment is the lack of inputs.....

I'm waiting for help as i'm completly lost with this one.

[jaycee]

Connect your PC straight to the LAB IN input. Don't have your PC's volume up very loud as this will bypass the volume control on the amp!

Do you get sound then?

[tenzz]

I tried that but i get exactly the same noise, only much louder

[jaycee]

Did you remove the link between PRE OUT and NORMAL IN and try that?
It's likely then that the power amp is damaged, probably blown outputs. Replacing them on the 3020 is unfortunately not a simple job as the circuit must be altered to be able to use newer transistors. It's doable, but requires some skill to perform the work.

[PLB]

Hi tenzz,

1) You say in your post "the only thing that comes from the speakers is a noise (quite strong)." Does the intensity of this noise change when you adjust the 3020's volume control ?
2) Have you tried replacing the cables that connect from your computer to the 3020 ?
3) Have you tried connecting another source to the 3020 input, like a CD player with new RCA cables ?

PLB

[tenzz]

When i connect my pc to the LAB IN and remove the links between the PRE-AMP and the NORMAL IN i dont get any sound from the speakers.Not even a hiss.

Concerning your question PLB,

1)yes, the noise goes up and down according to the volume pot.

2)I've tried 2 different cables.Both deliver the signal.(Checked both)

3)I've connected an portable mp3 player but its still the same situation.

I hope its not as bad as it seems....

[jaycee]

If you're getting no sound with the link removed and audio source connected straight to LAB IN, the power amp stage is not working, although if youre hearing nothing thats strange.

http://www.diyaudio.com/forums/showt...?postid=859668 This thread has some good information, and a link to the service manual showing the circuit diagram.

If you haven't already, it might be worth opening it up and checking the fuses are intact.

Oh, just in case you happen to be close by, where about in the UK are you?

[tenzz]

I have already opened the amp.
-The fuses are ok
-no blown or leaking capacitors (though they are the originals so i will change them sometime in the future)
-no obvious bad solders (i didnt check with the multimeter cause i'm not very confident working with high voltages....)
-no dust

Btw, can i check the voltages with my cheap (3quid) multimeter or it will melt in my hands?

ps. i am in Scotland

[jaycee]

You can check, but as you say you are not confident working with high voltages, and you would have to do this with the unit open and turned on, I wouldn't advise you try.

I wouldn't say the amp is beyond repair but it does need to be looked at by someone with some experience. With that comes the cost of someone's time, which is unfortunately why a lot of stuff is "not economical to repair"

If you had lived near me I would have offered to repair it for price of parts.