What is the function of a "keeper" disc?

[ofajen]

I have 2 Shure SM-81 capsules and 4 SM-80 capsules, but only 2 SM-81 bodies, so I have at least four stored capsules at any one time. One pair of the SM-80 capsules came in original plastic cases for the R104 replacement cartridge for the SM-81. On the box it says "when stored, keeper (black foam disc) must remain on terminal." The "keeper" disc is a little foam disc with a center hole that fits on the end of the capsule electrode and it pretty much just fits inside the empty part of the capsule and just touches the threads on the inside of the capsule.

However, I only have one keeper and four stored capsules. What is the function of the keeper disc? If it's important, is there a way to obtain material to make more? I can't seem to find anything about it on the Shure website under accessories. Is it just supposed to keep the inside of the capsule clean and dust free or does it serve some other, mysterious, quasi-electrical function?

Cheers,

Otto

 

[crazydoc]

I don't know if this is pertinent in this case, but if there are any capsule components that are sensitve to electrostatic charge, the black foam is conductive and serves to keep everything at the same potential - that is, it will prevent the buildup of a charge that might discharge (spark) from one component to another.

 

[ofajen]

I don't know if this is pertinent in this case, but if there are any capsule components that are sensitve to electrostatic charge, the black foam is conductive and serves to keep everything at the same potential - that is, it will prevent the buildup of a charge that might discharge (spark) from one component to another.

That's the one other thing I suspected it might be for. I think I could handle that issue by making sure I always put the keeper on the capsule just prior to reinstalling it on the mike body. Thanks!

Cheers,

Otto

 

[dgatwood]

That's the one other thing I suspected it might be for. I think I could handle that issue by making sure I always put the keeper on the capsule just prior to reinstalling it on the mike body. Thanks!

Cheers,

Otto

You could always wrap a little piece of wire across between the terminals or just grab the anti-static foam off of almost any silicon chip you can buy at the Rat Shack. That said, it is probably more for protecting the contacts from physical damage than anything else.