Neumann M149 Polarity Switching Noise

[FPALB]

Recently got in a M149 into the shop and its sounds great, but occasionally when the polar patterns are changed the signal is still passed, but its bombarded with noise that sounds like a snow storm for a about 8 seconds and then it stops and sounds great again. Struggling finding any schematic for this mic, but im assuming its a stray voltage being held in a capacitor some where.

Anybody have any insight into this?

 

[kingkorg]

This is perfectly normal. Turn down the pre when switching patterns.

 

[RuudNL]

It seems Neumann considers this as 'normal'.
As normal as the loud 'bangs' when switching the pattern on a U87...

 

[FPALB]

Thanks!