Hi there

Long time no post :( something like 7 years!

Anyhow, after a long hiatus, my home studio is back up and running since the new generation of my family have found music...

I opened up my Oktava MC012's - 1 body, 3 capsules, a metal mount and a -10db pad in a plastic case, and to my horror, not only has the foam deteriorated to a sticky mucky mess, but it has adhered to the paintwork of the microphones and reacted with it
to cause pitting to the satin nickel finish.

Any idea if I can remove the muck? mics still work OK but they look awful...

Thanks
Angus

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Angus Kerr <angusjmkerr@gmail.com> wrote:

Anyhow, after a long hiatus, my home studio is back up and running since th= >e new generation of my family have found music...

I opened up my Oktava MC012's - 1 body, 3 capsules, a metal mount and a -10= >db pad in a plastic case, and to my horror, not only has the foam deteriora= >ted to a sticky mucky mess, but it has adhered to the paintwork of the micr= >ophones and reacted with it to cause pitting to the satin nickel finish.

This is the same urethane breakdown process that causes sticky shed on tapes and speaker surrounds to fall apart!

Rubbing alcohol should remove it although you'll still have that finish pitting underneath. If alcohol doesn't do it, try naptha. Don't get it into the vents!
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

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Scott Dorsey wrote:
================

This is the same urethane breakdown process that causes sticky shed on tapes and speaker surrounds to fall apart!

** Plus the fine, coil springs of reverb tanks.
Certain Accutronics models have a foam pad that damps coil impact with the floating tray.
It rots and coats the 4 or 6 springs in tiny particles of goop.
Net result is next to no reverb.

Rubbing alcohol should remove it although you'll still have that finish pitting
underneath. If alcohol doesn't do it, try naptha.

** Yep, naptha or else acetone is the cure.

Damn hard to successfully apply all along and inside a long coil spring.


.... Phil

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On Saturday, May 14, 2022 at 1:02:00 AM UTC+2, Scott Dorsey wrote:

Angus Kerr <angus...@gmail.com> wrote:

Anyhow, after a long hiatus, my home studio is back up and running since th= >e new generation of my family have found music...

I opened up my Oktava MC012's - 1 body, 3 capsules, a metal mount and a -10= >db pad in a plastic case, and to my horror, not only has the foam deteriora= >ted to a sticky mucky mess, but it has adhered to the paintwork of the micr= >ophones and reacted with it to cause pitting to the satin nickel finish. This is the same urethane breakdown process that causes sticky shed on tapes and speaker surrounds to fall apart!

Rubbing alcohol should remove it although you'll still have that finish pitting
underneath. If alcohol doesn't do it, try naptha. Don't get it into the vents!
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Thanks Scott

I've got most of it off with Isopropyl alcohol, but the sticky much is awful. Not only does it stick, but it also seems to react with the paint... Unfortunately, the pitting is permanent, and some of the screenprinting (i.e. the polar pattern marking) also gets messed up by the muck.

It really is a pity..
Surprisingly, the mics work fine (mostly - one dead hypercardioid capsule)

Question is though, what can I use to replace the foam (that will not turn to glue)?

Felt?

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