Batboard

Have problem with HMN1022B Maratrac mics loosing sensitivity over time. Have confirmed the electret cartridge is the culpret. I have new mics that have great gain & have confirmed that stealing the cartridge from one of these new ones & putting it in the old mic fixes the problem. The replacement cartridges Motorola can still supply are better than the old ones that fail, but still not as sensitive as the ones I have in the new in the box mics. Anyone else seen this issue? I have some electret cartridges on order at this time from Digi Key in an attempt to find more sensitive ones. Appriciate any knowledge anyone has on this issue.

Steve H.

Steve,

How old are the microphones?

The origional mics are varied in age, some as much as 12-15 years. The mics I have that are still new in the box, we bought about 2-3 years ago. Just wish I could find new cartdriges as good & sensitive as the ones those new mics have in them. Motorola's replacements today are not as sensitive.

If the mics are 12 to 15 years old the electrolytic capacitor that bypasses the electret bias is old and dried out and needs to be changed.

Well I suspected that too, but changing the cartridge only is what fixes them.