nad 304 annoying fault

[ChocoHolic]

ughhh, quite inconvinient such sort of fault
... probably Chris is right...
good luck in finding the bad solder joint.

In first step you could suspect all mechanically stressed solder joints.
I.e. traditional suspects could be a solder joint of the input terminals on the PCB..

Don't worry if you don't find it the reason for the fault immediately.
I had a similar fault in an amp of an friend.
After 2 hours searching, I decided to resolder all joints.
2 more hours. No success.
I had to follow every PCB track systematically with the scope
and finally found a cracked track. The crack was so small that you
could not see it with your eyes, even after I knew where to look....

But before you start to much trouble in searching, you should first make sure that the speaker relay is really OK.
Let the musik play and measure with a DMM if the Signal is missing
on both sides of the related relay contact, or if it gets lost across the contact...

[jaycee]

I had a fault in an amplifier where the music would suddenly cut out with a loud *THUD*, intermittently and unpredictably. After checking the usual faults, and deciding that the STK chips were fine, i was flummoxed. It was only by chance that I noticed a transistor configured as a zener follower was cold when it should have been hot. Replacing the transistors made no difference however.

Poking around the area with a multimeter probe to check voltages, I slipped and hit a resistor. *THUD* the music came back on. It turned out the resistor was cracked internally even though on the outside, it appeared fine... and the -ve voltage to the preamp and frontend of the STK chips was disappearing.

It seems sometimes when it comes to fault finding, a certain amount of karma is involved

[anatech]

And of course you are correct. Good techs don't charge to replace the part, they charge to find the bad part and replace it.

-Chris

[sollerbeen]

After a lot of prodding about I still can't pin down the fault. On the whole I'm inclined to put up with it. It occurs less frequently now than it did a week ago. (I should mention it started after I had moved the amp. a few miles in the back of the car - with a fair number of road humps involved). About three out of four times the channel comes on instantly, on the remaining occasions it's on within about five minutes. I have noticed that the channel sometimes comes on at a reduced volume, jumping to normal vol. after a few minutes. I've also found that momentarily twisting the volume control to a high level will sometimes start it up.

Anyway thanks for the advice and suggestions. If the problem worsens I'm going to have to get more involved, but as I said before, it sounds great and I would really like to avoid resoldering every joint.

Thanks

Neil

[kbook]

This thread was a year ago but I found out that my NAD304 acts the same way where my left channel mute and unmute itself. I have to increse my volume up and then the sound came back. It is weird. I did the simple current and voltage adjustment. All values are ok. Furthermore, my problem seems to be a balance pot. When I turned to to the right channel, I can still hear the left channel.