Kinsler Hi-Fi Commentary
This text is present in the sci.electronics.repair FAQ web site, but someone had a copy and paste mishap or two when transcribing it. Fortunately, the original posting was archived by Google Groups, so here it is for your viewing pleasure.

I make no claim of any right to this material, its rights remain fully with the original author, who suggested that it would make good material for the SER FAQ. It's transcribed here only because the SER copies are all corrupted. The only thing that links to this page is my Insignia NS-R2000 review, so you can click here to go back OR you can just hit the back button in your browser to pick up where you left off.
One of the principal tenets of Kinsler Hi-Fi Service was:
The Customer is Always Wrong.

I doubt that it's a matter of volume or bass: these things will limit themselves pretty well.  What's happening is that the guy is short-circuiting his speaker wires.  He's either got another set of speakers that he uses for parties that he's not telling you about, or he has a set out on the porch with which to serenade the neighborhood. There's a bum splice in the wire that he doesn't know about, doesn't care about, or isn't going to tell you about.

They like to horse around with the speaker arrangements whilst under the influence, particularly at parties.  Or his kids borrow the thing and take it to a friend's house and hook it up to the Christmas lights to try to watch them flash with the music.  I am not making this up: I'll tell you the gopher story sometime.

The only way to protect yourself is to solder a couple of appropriately-sized fuses in series with the speaker lines.  Put 'em inside the case, and solder them directly in.  If you put them in a fuse holder, the customer or his minions will pull them out, replace them with 25 amp car fuses, blow out the IC, then replace them with your 1 or 2 amp fuses from Radio Shack, and claim ignorance of the whole thing.

Again, I am not making this up.  When I soldered fuses in, I'd get the sets back with what were supposed to be my original fuses taped in with scotch tape.  Once someone used a Band-aid.  But generally the solder keeps them out of there.  It's best, in fact, not to volunteer the fact that the fuses are in there at all.  If there are speaker fuses in there already, solder in your own in series with those.

The fuse size is a bit critical, of course. You can figure it out from the power and speaker impedance, but generally 1 or 2 ampere fuses are okay for anything that's made of plastic.  Use regular-blow fuses, not slow-blow.  Soldering fuses is easier if you use the Chinese ones that MCM sells--they're already soldered on the ends.  Expect to occasionally lose a fuse when you're soldering it in, but you get good at it fast.  If you use fancy fuses like Buss or Littelfuse, you have to file off the nickel plate from the ends to expose the brass.  That way, you can tin it quickly before the fuse wire detaches from the inside of the fuse.  Enclose the fuse in a piece of clear, non-heat-shrink tubing. Or often you can solder one end of the fuse directly to the circuit board or to the speaker connector. You have to use some imagination.

When the device comes back with the speaker fuses blown, just replace them at no charge--it's a fast job, and you'll know what's going on.  Then you can start quizzing the customer about his Experiments In Stereo Speaker Wire Science Whilst Intoxicated.  My favorite defense was, "No, I did _not_ hook up bad speaker wires to this stereo.  My brother did it."

Kinsler Hi-Fi specialized in crummy stereos for many years, and I put a pair of speaker fuses (and a power fuse, when that was missing) in just about everything that came in.  I used more fuses than anyone else in New Haven for a while, there. I still have a few cases of MCM fuses left over. This diatribe might be useful for the FAQ, I suppose.

                                        Mark Kinsler