I have a? Rode NT1 which is very simlar to the NT1A in many respects. There only appear to be minor differences to the schematic linked to in post #2 of this thread.
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I've had it for about 7 year now, and last year the sensitivity dropped dramatically. Almost no output.
I was surpised to find that the polarisation voltage across that capsule was way lower than it should have been - even though the voltage multiplier was outputting the correct ouput voltage.
It's not easy to measure the actual polaristion voltage directly with any accuracy -- connecting a DMM will shunt the output filter 4M7 resistor, so that the 73v voltage generator output will measure more like 50v.? ?In my case it was a lot lower than that - more like 10v !?
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I desoldered the final output capacitor ( on the NT1 that is C8 - the large 0.1uF cap adjacent to the? actual capsule termination pad. )? Underneath was what looked like dust. Removed that, and cleaned underneath with iso prop alcohol. Resoldered, and was able to measure the voltage across that capacior as 45v? (should be around 50v for the NT1-A).
Mic has performed perfectly since.....?
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(The actual voltage figures are slightly lower for the NT1 - it used a 13v zener as opposed to the 15v of the NT1-A.
The figures I describe above refer to the expected NT1-A figures).
