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NAD 304 AMP...No Sound at all on both channels, Black marks on inner case.

Hi Guys,
I have no sound on both cahnnels, Ive opened up the case and there are black marks on the top of the inner caseing. That doesnt look good at all, but there appears to be know burn damage to the board on the area this occured. Right below these marks on the inner caseing on the board are two glass fuses, they seem to be intacted as well. The amp powers up fine and shows the green indicator light. Simply no sound out the badger!

Thanks alot folks!!!

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  • sircuit84 Sep 27, 2008

    Hi

    Thanks for the swift reply. I think you may have hit the nail on the head. I read on a forum about

    the, pre out and main in section, has to be connected or no sound. Can you please tell me how to connect them and what is the purpose of them, as I dont have them on my other amp.



    I think you may have found the solution:)

    thanks alot dtaylor91

  • sircuit84 Sep 27, 2008

    Hi

    I now have sound out of the amp but it is silly quiet when turned up. Turned up half way I can just about hear it. Maybe I have a blown amp? It was picked up cheap second hand with a marantz cd player that works perfectly fine. I used a standard phono connection not very long as you said. But yeah just really low volume levels.



    Thanks for your last post seems like we are making progress:)

    all the best

  • sircuit84 Oct 23, 2008

    Hi

    Sorry for the slow reply internet has been down. On closer listening it does indeed disort at higher volume levels. But I thought I would give your fuse idea a go anyway. It can now at least be elimnated as it didnt change anything. So what do you think we might looking at here?



    Thanks so much for your last detailed easy to follow post!

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This may be a silly question, but the pre-out/main-in jumpers are installed, yes?

Posted on Sep 26, 2008

  • dtaylor91 Sep 27, 2008

    Just take a standard, but short, interconnect and plug the left pre-out into the left main-in, and the same with the right. That should take care of it. 


    The purpose of them is to allow for future upgrades. In other words, if you find a better preamp that you want to use, you can still use the 304 as a power amp only, by plugging the new preamp into the main in connectors on the 304. Or, you can use the 304 as a preamp for a different power amp.



  • dtaylor91 Sep 27, 2008

    OK, From that description the next thing to do, assuming the sound you are getting is undistorted, is to check the main power supply fuses. The other two fuses you described near the "toasty" area feed the preamp section only. If the preamp is fine, which from what you've said so far it is, it will drive the main amp enough to produce some sound even if the main amp is receiving no power at all. The key thing here is, is the sound you are getting out so far undistorted? If so, you may be ok after installing new main amp fuses. They are in dead center of the circuit board, two of them are 3.15A, and the other two are 5A. Use "fast-blo" fuses only. 


    With new fuses installed, leave the cover off the amp, DISCONNECT the speakers and the CD player, keep your hands well away from the amp, with the exception of using one to press the power switch while you are watching those new fuses. If they immediately blow on power-up, there will be a bright flash, and then we'll have to discuss replacement of quite a few large power transistors. 


    If they don't blow on power-up, it will appear nothing happened. Turn the amp off, connect the speakers only, leave the volume knob all the way down, and turn the amp on again while you watch the main fuses. If they blow THIS time, there are issues with the main amp that will take more to address than I can do without sticking my head into it myself (will a boatload of test equipment). However, if the fuses don't blow on this second try, start slowly turning the volume knob up while you keep an eye on the main fuses. If they blow at a certain point on the volume knob, there are issues in the preamp that will need to be dealt with, but this is very rare with the more vintage NAD preamps. You are more likely to be hit by lightning sitting in your living room than the preamp having blown!


    IF the fuses have survived so far, you SHOULD (fingers crossed) be home free. Connect everything up and give it a listen.







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