Shure KSM44 Noise

[kingkorg]

Hi guys.
I have spent several days trying to fix random popping and cracking noise, fairly quiet one, in my KSM44 and now I am getting sick of it. I changed almost all of the SMD caps (including notorious 120pf), measured everything and it just won't go away. Tried different preamps (phantom power), removed capsule, nope it's still there.

I am still waiting for response from Shure regarding replacement PCB boards, but I have no idea which one if them is it. There is two of them, preamp and power supply.

I went through this thread and my circuit looks similar as far as I can tell.
https://groupdiy.com/index.php?topic=61079.0

Question is, does anybody know if this mic has any internal EQ going on, or is it just a clean preamp transferring pure sound of the capsule? I might just replace pcb with something else, but what would work well with this capsule?

 

[Khron]

Replace whatever other pF-range caps there are left. As you might've read on my thread, i still had noise after replacing all the 120pF ones mentioned in that Shure service bulletin(?).

It only went away after i replaced all the 68pf caps as well, with 120pF ones ('cause i had ordered a batch of 50, and i had several to spare)

It's sort of sadly ironic - they went to all the trouble of "bulletproofing" the circuit against RF and oscillations with all those small-value caps, only for those to crap out and CAUSE noise...

 

[Khron]

At least in theory, i guess so - many of those 68 / 120pF caps are there to shunt away excessively-high frequencies (EMI / RFI).

 

[Khron]

Glad to hear (no pun intended) that 1) you found the (other) culprit, 2) that i could help, and 3) that it's all good once again!