Akg p420 failing. Low cut problem.

[huehu3gg]

well the mic have his years, many time i disarm and clean. one of the 2 diaphragm are no flat, like it was manipulated, the front one. so i change the rear diaphragm into the front. that was nice.
but if i dont use de low cut, see the images, i got a really low cut, and when i use the low cut, i win more "low end". i think its the real low cut, but the FLAT isnt working... or just cut something that no suppose to...
sorry for my english!.

question about diaphragm: as i say its manipulated, someone touch it or disarm and reassambly, looks weird, that can cause the sound dissappear with high air pressure? maybe i can fix by reassambly? or any other technic to "flat" the diaphragm?

im noob in microphones, but im professional of microsoldering. i repair motherboards and GPUs. got lab and tools to do it.

 

[huehu3gg]

any help? or suggestion to check?

 

[Khron]

Perhaps some of the ceramic capacitors involved in the low-cut filter have failed (internal short-circuit, and associated loss of capacitance)?

Later edit: See the clump of capacitors on the right side schematic in this post:

https://groupdiy.com/threads/akg-pe...min-mod-p200-p100-p400-p420.67473/post-865741

If really necessary, i might consider removing and measuring those in one of my Perception 200's to verify the values.

 

[huehu3gg]

You mean the FET Board ?

 

[Khron]

You mean the FET Board ?

Did you even click on the link in my previous reply?

 

[huehu3gg]

of course i do! the hand writing schematic! but i dont understand wich clamp of caps u said.

 

[Khron]

Clump, bunch, group of capacitors, next to the 3-pin P2 connector (at least on the schematic).

I would guess the capacitor between the 15k and the 110k resistors, and/or the one between the 110k and the 1meg, might be unwell. Can't quite tell which of the others is in-circuit in the "flat" position of the switch though...

Took a peek inside one of my Perception 200's, and measured those four capacitors (removed from the board). Can't vouch for the accuracy of the values of two of them, since they were quite a bit off from any standard E24 values, even - one measured 6.33nF, which would be sort of at the top end 10% tolerance of the standard 6.2nF, and the other showed 6.5nF, which could be at the bottom end of the 10% tolerance of a 6.8nF.

 

[huehu3gg]

oh really thanks!! i will check! how they are. its strange cause before i clean up, the low cut works perfectly. after assambly, pum! super low cut when he's off haha. thanks man