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View Full Version : Cleaning L100A N100 crossover sealed L-pads



spin156
02-19-2008, 05:39 AM
Sorry about the long thread title ...

I am new to AH and am restoring a pair of L100A's. I spent over 35 years as an electronic tech in all kinds of applications. But, not audio.

Anyway, I have spent a lot of time researching my rebuild and one question that seems to come up a lot but never gets answered (at least I could not find it) is how to clean these "sealed" L-pads.

It's actually pretty easy. With the L-pads still attached to the N100 board, I just used a pair of water pump pliers and opened them up to the correct width to match the diameter of the L-pad casing. Then I gently grabbed the metal casing with the pliers and gently pried it off. It came off pretty easily, exposing the wiper and the winding. So, these babies are no different from any other potentiometer or rheostat you'll open up and I was surprised that the windings looked very clean - after at least 35 years (yup, started in electronics and bought the speakers the same year). That being said, it's assumed there is some oxidation on any copper that's been around for that long.

So, I then cleaned up the windings with some Deoxit (any contact cleaner should work just fine) and tested some signals through the L-pad. I am using a Leader wave generator and a Tek 2465 scope to monitor. I had checked the signal before the cleaning and after and it was definitely not as noisy when turning the wiper.

I cleaned hundreds of padded potentiometers on analog computer based flight simulators in the Air Force and cleaning these L-pads is no different. Just liberally hose the windings with your cleaner and turn the wiper back and forth fifteen or twenty (or, whatever you like) times. Works fine.

Hope this will help someone.

Great forum, folks! I'm very grateful to find this resource. I also have joined the AK forum and it's excellent ;-))

Cheers,
Bill