Microphone Oktava 219A stopped working

[Khron]

Re: Microphone Oktava 219A stopped working

That's great to hear Congratulations

Yes, all the solid-state condenser mics nowadays (non-electret) use "normal" 3-legged JFETs

I've used a small blob of cotton wool (the "bulk" stuff, for medicinal use) and 99.8% isopropyl alcohol (IPA), wrapped quite tight around the (closed) tip of a pair of tweezers. This, plus a bunch of patience, lots of care, and a light(ish) touch worked for me, so far

[SteveNielsen]

Re: Microphone Oktava 219A stopped working

The grounded metal case on the old JFETs was to shield out noise that earlier designs were susceptible to. Modern replacements have been improved to the point they no longer need such localized shielding.

After cleaning the capsule dry it very thoroughly before powering it up. They are susceptible to moisture damage. If you power one up damp kiss it good-by.

[skunks]

Re: Microphone Oktava 219A stopped working

Thank you guys!
Will simple ethyl alcohol 96% work?

Modern replacements have been improved to the point they no longer need such localized shielding.

Does it mean I can use 3-leg JFET and dismiss connecting ground? If the only reason of ground connection is shielding, that modern JFETs doesn't require.

[Khron]

Re: Microphone Oktava 219A stopped working

Mylar (the most widely used diaphragm material) shouldn't have any problems with ethyl alcohol either. I found this table from DuPont:

https://cdn.badcaps-static.com/pdfs/...1144ab4fdb.pdf

Older condenser microphones (think vintage German / Austrian mics, the likes of Neumann U47's) had diaphragms made out of PVC, which ages far worse than mylar, but shouldn't have issues with ethyl alcohol either (scroll down to page 8) :

https://cdn.badcaps-static.com/pdfs/...cf8a5fbfd5.pdf

And yes, 3-legged JFETs are fine

Just last week, i did some work (mods & upgrades) on a pair of sE 2200A microphones i have. Up-rated the electrolytics, did a bit of re-wiring on the front-end (including replacing the stock 2SK30's with a pair of manually-matched Vishay-Siliconix J305's), and swapped the two ceramic caps for a pair of film caps.

[redwire]

Re: Microphone Oktava 219A stopped working

skunks, I would leave the JFET alone. Toshiba discontinued the part early 2003 I think. It affects the sound quality a lot.

JFETs have huge variations from part to part, so there are 3 classes for IDSS (2SK170GR or BL or V) and many times they are usually hand-picked to bias for best dynamic range.
Micross makes equivalents.