Destroyed front diaphragm on a brand new K67

[emrr]

Oh yeah, spill a soda or beer in electronics, chase immediately with water in a way that can drain.

 

[MicMaven]

. . . your looking at half life of around 12 hours , ie your still 50% stoned when you wake up next morning where the effects of smoking a joint wear off after only a few hours . . ..

And now you know why I stick to a short shot of Bourbon! Expert witnesses in Court posit one metabolizes has a full oz of juice in just one hour! (I once hired a psychoneurophramacologist to support a case . . . with a moniker that long, he cost plenty! ) James

 

[Tubetec]

Did you ever see what a pint of Guinness does to a mixers insides ?
its has iron in it and is way more conductive than beer , if you dont shut the power down before the liquid hits the pcb its like throwing a crowbar across the PSU rails .

Ive a small Uli Beh mixer for around 25 years , guy who bought it off me spilled his pint of black stuff on it , our tech department said it was unservicable , so it ended up with me ,
Took a few good washings down with finest 80+% moonshine , a shorted op amp in the aux return path desoldered and it worked again , led meters remained funky ,so what ,
I use my ears not my eyes to detect objectionable distortions .

 

[GeorgeToledo]

It’s tape that’s supposed to have high bias, not the tech!

 

[Delta Sigma]

Finally got back to this U67. Still having issues with polar patterns.

Cardioid sounds fine. Rear diaphragm in omni is significantly quieter (maybe 6db or so) than the front, with a slight inner tube sound. Rear diaphragm in fig-8 is significantly louder (maybe 4dB or so) than the front diaphragm.

I swapped in a K47 and the problem did not exist on the K47.

I pulled the front/back halves apart again to check orientation. They can only be joined two way, 180 degree difference. Hole pattern lines up the same both ways. No change with the new orientation.

The rear diaphragm (originally the front), which was damaged, has returned to looking perfect and measures identically to the front diaphragm (58pF). The backplates show continuity, as they're mated with a metal spacer. I have KK67 head pin 1 (60V backplate connection) to the rear backplate, and have yet to try an external wire to couple them together. Seems unlikely to help since there is continuity between them.

I didn't expect the damaged diaphragm to have close enough freq response that the patterns are perfect, but this seems strange to me. Really frustrating one.

Anyone have any ideas that could steer me in the right direction? @soliloqueen?

 

[soliloqueen]

unfortunately it sounds to me like the integrity of the rear membrane was compromised. there's probably nothing you can do short of reskin the rear side unless you really wanted to experiment