Potato Cakes
Well-known member
Hello, everyone,
Years ago I modded two CAD GXL3000 with a Linear 87 mod from Microphone-Parts.com. I changed out the capsule and the kit changes out of the two stock boards, which has the FET, capsule connections, and the DC blocking cap on the FET drain. It worked wonderfully until about 6 months ago when audio would die when you started talking into it. When you stopped talking, you could hear the audio come back and any low level ambient noise that was in the room. You resume talking into it and it would work for about 5 seconds then die again. Then the ambient noise. Then repeat. I started with changing out the FET but that did not solve the problem. I did notice that the voltage on the source of the FET (2N3819) was about 2VDC when it was "working" with just low level ambient noise. When you talk into it and the audio dies, this measure 4V and stays there till the audio comes back. On the stock board that was left, there is a 2N5551 in place of the 2SA1015 which I don't believe I changed.
To me it sounds like the voltage on the capsule it self is being drained completely when you speak into it and then it recharges when not in use. The electrolytic capacitors in that would be connected to phantom power test fine, so I'm suspicious of the capsule even though I've never seen this happen. The 2N5551 could have something to do with it but doesn't explain the voltage change on the source connection of the 2N3819 that corresponds to when the microphone does and doesn't pass audio. Curious if anyone else has seen this and if I'm way off in my current assessment.
Thanks!
Paul
Years ago I modded two CAD GXL3000 with a Linear 87 mod from Microphone-Parts.com. I changed out the capsule and the kit changes out of the two stock boards, which has the FET, capsule connections, and the DC blocking cap on the FET drain. It worked wonderfully until about 6 months ago when audio would die when you started talking into it. When you stopped talking, you could hear the audio come back and any low level ambient noise that was in the room. You resume talking into it and it would work for about 5 seconds then die again. Then the ambient noise. Then repeat. I started with changing out the FET but that did not solve the problem. I did notice that the voltage on the source of the FET (2N3819) was about 2VDC when it was "working" with just low level ambient noise. When you talk into it and the audio dies, this measure 4V and stays there till the audio comes back. On the stock board that was left, there is a 2N5551 in place of the 2SA1015 which I don't believe I changed.
To me it sounds like the voltage on the capsule it self is being drained completely when you speak into it and then it recharges when not in use. The electrolytic capacitors in that would be connected to phantom power test fine, so I'm suspicious of the capsule even though I've never seen this happen. The 2N5551 could have something to do with it but doesn't explain the voltage change on the source connection of the 2N3819 that corresponds to when the microphone does and doesn't pass audio. Curious if anyone else has seen this and if I'm way off in my current assessment.
Thanks!
Paul