I've got a Hisonic HSU8400L wireless system (quad receiver, 4 bodypacks each with 16 selectable channels). My problem is that the bodypacks themselves are microphonic; rubbing or tapping them generates audio noise that's almost as loud as the real microphone signal. The noise is generated even when the microphone is unplugged and the transmitter is muted. Since these things rub against clothing all the time this problem makes the units pretty much unusable. Any ideas?

SOURCE: Audio feedis crossing with my speaker feed with and without the microphone plugged in.

Your mic still picks up sound when it's unplugged ?
As far as the other prob goes that sounds like howl round ( feedback ), mute the mic when not talking through it or get a mic with a cardioid polar response pattern ( just ask for a cardioid mic, can get a hypercardioid or supercardioid too but a cardioid would be best for your application, point the mic right at your speaking position with the back of the mic pointing at the speakers wich ideally should be behind the mic, this will help cancel out their sound, puting a limiter on the mic and setting it where it only starts picking up sound when you talk directly into it will help too, but the sure fire way to solve the prob is to mute the mic when not speaking into it. What you definitely don't want is an omnidirectional mic, for what you are using a mic for. 

SOURCE: Pro. 2 WM-795V Wireless Problems

The mic volume is to loud. Turn it down a little.

electronic & computer repair& servicre

• 12061 Answers
• Posted on Aug 25, 2010

SOURCE: I own a Samson Synth

Hi, Radio Mic's can be great tools, but are devils for going faulty. They generally use an Electret Mic, this Mic requires Power to make it go. (Many problem are caused by Bad batteries, so these must be checked, and ideally swapped for known good ones. Also Check the battery connector too, it must be intact and clean and shinny, give it a rough up with sandpaper if unsure. Another point of failure is the On/Off switch, the battery side connection often comes off, and needs to be re-soldered) Anyway the signal from the electret. this then drives the FM transmitter, and the received signal is decoded, and you can hear it.
Now, you say that there is a "pop" when it is switched ON, well this at least gives us some hope, It is very ODD that BOTH of them are "Faulty" ? I would tend to look elsewhere? IF after you have checked out all the points I raised above, are attended to. and the Mic's check out OK. Maybe they have drifted off frequency, often there are trimmers inside the receiver to adjust..
Now these units can be obtained on eBay and the like very inexpensively indeed. As for repair again, eBay is the best.
If you can tune the transmitter, or know the frequency to tune the transmitter to. Now, then what I have done in the past is obtained a FM Transmitter Mic, kitset, made the kitset up, and then ripped the "Old" electronics out of the :"Old" mic housing and shoehorning in the new working kitset. tuned into the Receiver.
Always get a pair working standalone first, then after you get the Mic working out through the receiver, then, and only then use the receiver with "Other" things.

SOURCE: Wireless Microphone low volume

The PGX1 bodypack has a switch on the side to set the gain. Make certain that switch is in the "mic" position. Otherwise, simply turn up the volume on your mixer.

SOURCE: When one of my co-workers

Yes, it can be repaired. Send it in to Shure. www.shure.com/service