I have difficulty repairing an old u87 and really need some help. I don’t have much experience with microphones.
There have been previous repair attempts here and I have also done a couple of things.. I checked the components, and the connections, changed the electrolitic caps, corrected a few connections and soldered a new 2n3819. There still are problems.
My soundcard can receive the signal from the microphone, but there is no amplification.. The signal levels on the drain and the gate are similar. Instead of the resistor I have put a trimpot on the source, which doesn’t effect anything. I have checked the caps and they seem to be okay. I might be missing something obvious. Any ideas?
The voltages also seem to be low (without the capsule and an input signal). It is possible that my soundcard is unable to supply enough current.. I don't think that is the reason, but I will also check that.
There have been previous repair attempts here and I have also done a couple of things.. I checked the components, and the connections, changed the electrolitic caps, corrected a few connections and soldered a new 2n3819. There still are problems.
My soundcard can receive the signal from the microphone, but there is no amplification.. The signal levels on the drain and the gate are similar. Instead of the resistor I have put a trimpot on the source, which doesn’t effect anything. I have checked the caps and they seem to be okay. I might be missing something obvious. Any ideas?
The voltages also seem to be low (without the capsule and an input signal). It is possible that my soundcard is unable to supply enough current.. I don't think that is the reason, but I will also check that.