I have a lot of experience with WL-93's, and everything everyone else is saying is pretty much dead on. A new one can be had for around $70US from certain suppliers. The problems I run into most are either the
element itself wearing out (gradual loss of sound no matter the
gain setting, fading in or out, a very tinny or distant or "paper towel tube" sound, having to EQ the daylights out of it,
etc) or a simple short or broken
wire, usually an inch or two up from the
connector. The broken
wire part is easy to fix, if you're handy with a soldering
iron - find the short by wiggling the cable working up from the
connector until you don't get bursts of static or cut-outs anymore, snip the
cord about an inch above that, resolder the
connector from the snipped section to the mic, and you're good to go. I've got a few formerly 4' cords that are now closer to 3' after doing a few of these fixes over time, but as long as the quality is still there I'll do the fixes.
Basically, if there's no sound or or if there are static bursts based on actor/mic movement, warm up the soldering
iron, and if it's a sound quality degradation issue, warm up the wallet.