Expert: cleggsan - 11/3/2009

Question
My audio receiver started making a loud popping noise through the speakers, and no longer has any volume. Can I repair this? I've checked my speaker wires and they seem to be fine. Thank you in advance for your assistance.
Craig
I am both a master electrician and class a a/c and refrigeration here in Texas

Answer
This is a vintage receiver!   And a good one, too.

Popping sounds are most often from a bad coupling capacitor.  They get old and start leaking or go open circuit with applied voltage which gives them a quick rc time constant change which will generate the popping sounds.  It can also be from an old or  worn potentiometer in the volume control or tone control circuits.

To check the volume and tone controls, just turn the unit off and rotate all the controls through their range several times and see if that cleared it up or improved the popping noises.

But, my guess would be one of the coupling capacitors.  If the popping continues when the volume has been reduced to zero it means the popping is coming from the circuits after the volume control.  If the popping goes up and down with the volume control it means the cause is in the front end.  If you switch to aux in and it goes away it means the popping is coming from the phono preamp stage.  Doing these checks you may be able to isolate it to one section of the amplification chain.  OR, you can merely replace all the coupling capacitors - which is what a tech would do when revitalizing the system.  

The coupling capacitors can have appearance of round tubular components with leads out each end or round like a coin with two leads spaced a little apart.  Here are what some of them may look like:

http://tp01.com/etutorials/images/capacitors01.jpg

And, you can take them to an electronics store such as Radio Shack and they can usually tell you what the value is and give you and equivalent unit.  Cost is generally a few cents or a couple of dollars.  

You will need a small, needle nose soldering iron to get the old ones out and solder in the new ones.

Hope this helps. Let me know if you need more.