MCA SP1 (MXL603 circuit) noisy (static storm) while "warming up". Where to look?

[777funk]

I have a couple of these and both work pretty well. But one seems to take about 30 minutes of being on with Phantom Power to lose this static storm noise (at least as loud as the signal). It doesn't go away by knocking the mic into my hand like a bad solder joint sometimes may. My guess is a bad electrolytic cap somewhere. Am I on the right track?

 

[Khron]

Got a voltmeter / multimeter?

 

[micolas]

I have a couple of these and both work pretty well. But one seems to take about 30 minutes of being on with Phantom Power to lose this static storm noise (at least as loud as the signal). It doesn't go away by knocking the mic into my hand like a bad solder joint sometimes may. My guess is a bad electrolytic cap somewhere. Am I on the right track?

When you blow into the microphone, do you speak loudly up close, does the signal break?
You should thoroughly clean the pcb and the components at the jFET input, with isopropyl alcohol, but not with cotton wool, lint remains, thin threads stuck, impregnated with residues. Over time, oxides appear that compromise proper operation.
If the cleaning doesn't work, only then move on with other investigations.
Depending on the test with high SPL you can appreciate if the capsule is defective.