Subwoofer no longer produce base sound

I would check the caps on the power supply. They are rather large electrolytic capacitors that will look like they burst and/or leaking. When these die, the caps ground and the sub will make a loud buzzing sound. If you are handy with a soldering iron you can replace them yourself. Replace them with the same voltage or a little bigger and same with the size.

If the cap. says 16v 4700pF on it, for example, a 20v 5300pF or a 16v 6200mF cap. will work for this application.

HAVE YOU CHECKED THE SOURCE FOR THE INPUT SIGNAL ?

Normaly C26 has turned bad. It's 22uF/25V and is easy to access when module is disassembled.

The transistors at the output stage of the sub amplifier circuit might be shorted so each time you power on, the circuit draws a very high amount of current which causes the fuse to blow. It's definitely a problem with the circuit so using a higher current rated fuse would probably just result in damaging the amp even more. You should ask a qualified electronics technician to take a look at it. I hope you can fix it.

Some specific model numbers might lead us to specific manuals and specific instructions.

Depends on your source and its amplifer complement. Some can drive a subwoofer directly while others just produce a Line Level subwoofer output for use by a separate amp feeding a subwoofer or self-amplified sub.

The set-up of the source to produce a subwoofer output is totally dependent on its design. Generally, you have to 1) tell it you have a sub, 2) define how bass will be routed or shared among your various speakers accordingto their bass-handling capacities, 3) using test tones, set the relative ludness and crossover settings so you have a uniform sound field.

To find a manual, maybe run it by the manufacturer

I saw this post. I have the same problem with my 10-100.
http://www.fixya.com/support/t2753393-klh_subwoofer_about_6_yrs_old_keeps

Did you ever find a solution for this problem? I have the exact same thing happening with my KLH subwoofer and I'd love to know how to fix it!

Sounds like the hum might be mains hum caused by the failure of the power supply capacitor(s) in the sub. It/they will be the largest on the pc board. You will find all the details (needed to replace it) on them. If you find more than one replace both.

make sure you have the speaker connection right if you do then it is a ground problem try plugging it in a different outlet

The 'Subwoofer' output on your receiver is used to connect to a powered subwoofer with a built in amplifier. Your KLH speakers use what is called a 'passive' subwoofer, it gets its power from the receiver and then passes the higher frequencies to the left and right front speakers after taking out the low frequencies for the subwoofer. A speaker system with a passive subwoofer is good for casual listening, but a powered subwoofer is required for really hearing low frequencies and rumble in movies. The KLH speakers you have were highly rated in their time for their price. The four satellite speakers and center channel speaker have very good sound compared to the little 'midget' surround sound speakers most people buy today.

Here's how you hook them up:

- The left and right front channels from your receiver terminals should go to the terminals on the subwoofer marked 'From Amplifier'
- Your left and right front speakers are then connected to the subwoofer terminals marked 'To Speakers', they do not connect directly to your receiver.
- Your center speaker is connected to your receiver terminals marked 'Center'
- Your rear speakers are connected to your receiver terminals marked 'Surround'

That should get you up and running. If the bass isn't good enough with the passive subwoofer, you can get a decent powered subwoofer like the Velodyne VX-10 for about $150 and 'kick it up a notch'. Good luck and enjoy....