Schoeps CMC641 hiss problem

[camarada78]

I have a Schoeps CMC641 (CMC6 body with MK41 capsule) on my bench with a somewhat audible high frequency hiss.
The microphone works but this hiss is 6-8dB louder than its pair. Usable but not high quality as it should be. Its not the capsule because we swapped and the problem remained. I think it might be one of the caps but since the circuit is very delicate (small smd stuff) i want to be sure before fully dismantling and applying hot air.

Anyone had similar issues that can give me some help?

 

[Khron]

Might want to see which caps filter the capsule bias voltage. My Rode NT2-A's noise issues were caused by one of the big SMD film(!!!) caps that was filtering the bias to the front diaphragm.

 

[camarada78]

I only have the schematic for the vintage CMC5, not these modern CMC6. The main difference appears to be on the power supply side but - if my smd code reading was right - these Zeners for example are not anywhere in the vintage cmc5.

 

[camarada78]

Just posting un UPDATE:
It was the electrolytic caps. Stock was a no brand smd 22uF 40v and I changed them to Samwha (Korean cap) 22uF 50v and now it's even more silent than the original.

 

[camarada78]

A newer update lol. The hiss is gone and the mic is very quiet again but now the low end is not as good as it was before, very little presence. I will test other brands i have around: EPCOS and Panasonic.