condenser mics

I don't think they are noted for it but there are a few websites that mention charge leakage in electret microphones.

Some types of condensor microphone have active polarisation. Electret microphones have charge trapped in a plastic film.

Here is a website with a comment saying "It used to be that the charge would leak off in a few years, but that has been solved. It also used to be that electret microphones were inferior to externally polarized condenser microphones. That, too, is no longer the case."

I can't find it now but I vaguely recall reading somewhere that condenser microphones from the 1960's and 1970's may not work due to charge leakage.

Radio transmitters generally have automatic gain control on the audio so a small drop in the microphone sensitivity should not make any difference.

There might be other reasons for a microphone to produce bad sound after years such as the plastic film decaying or it being gunged up due to being owned by a heavy smoker. I had a few bits of secondhand radio equipment that stank due to being owned by smokers.

I expect some of the older people here who have been doing audio for many years will have somthing to say on the subject. You could try asking an audio group.

Bob

I purchased a electra 2 wire mic from the shaft and will temporary solder it in to take measurements.

From what I can gather, it appears the audio is nasally sounding and seems only to be responding at high output in a narrow portion of the audio spectrum, this is taken from the element output.

I also noticed noise at the element that seems to me, excessive.

Thanks.

It it an electret or a condenser?

No, It's a condenser mic. 2 wire, 1k Ohm loads 60db S/R etc..

I resolved the issue. I had two units of the same ventage with this problem. I replace the mics

Audio is back to specifications.

Thanks.