Crown GLM 200 Condenser Making "Rice Crispies" Sounds

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headstack

Member
Joined
Jun 17, 2012
Messages
15
Thought this could be (a) a bad FET, (b) a cap in the phantom circuit gone to heck, (c)etc.,
traced it to this weird setup.

These little "cups" seem to contain some sort of conductive goop that has dried out, allowing the resistor to make a capacitive connection that sputters horribly.

However, bridging the "goop" with a little solder creates a state of lower output, and rolls off a lot of high frequency, so I guess the "goop" is something rather special.

Any ideas as to what the heck this stuff is, and what might be a worthy fix?

BTW, that's an smd peeping out from under the resistor, not an errant glob of solder from my hasty bridgework and removal.

Thank you

GLMpcb_zps46d752a2.jpg
 
INHO the 'small cups' look like feedthroughs, they should not be bridged.
How does it look at the other side of the PCB? How are the wires of the resistor connected?
 
The cups are soldered through the board into pads with one side mating to board on that side, the othe cup connects to the smd, the resistor is literally squished into the goop... Barely!

When I gently flex the board the smallest ammount, the mic works properly.

While chopsticking the circuit very gently, it was apparent this resistor was the culprit, and it can be lifted free with a very light touch.

Had to clean the flux off the board to see everything on the far side, so will grab a shot of this for you.

I have never seen anything like this before!
 

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