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Re: Humidity (?) problems with a Sennheiser MKH20

Subject: Re: Humidity (?) problems with a Sennheiser MKH20
From: "Magnus Bergsson" icelandnature
Date: Tue Mar 26, 2013 7:27 am ((PDT))
Thanks for your answer David


--
Bestu kve=F0jur / Best regards
*Magn=FAs Bergsson
*Tel: + 354 6162904*
*
http://fieldrecording.net





On Sun, Mar 24, 2013 at 5:26 PM, Avocet <> wrote:

> **
>
>
> Magn=FAs,
>
> I've got the old MKH400 series mics some of which date back to the
> 1070's and they are very robust. Current models are a slight
> improvememnt over what was always good specs but perhaps not quites as
> robust.
>
>
> > Is it mainly capsule or circuit problem?
>
> Condensation or liquid water will always cause problems and if a mic
> gets wet or damp, it is probably unwise to heat it up (as with any
> electronic gear) as that can drive moisture deeper. Let wet gear dry
> slowly in a dry place. I've just written about silica gel and I sue
> woollen cloth which has been freshly ironed or heat dried.
>
> MKH series mics use a lower voltage across the capsule and a high
> frequency bias instead. This has two benefits - less likely to "track"
> across moisture, and a low impedance. Other mic capacitors have a very
> high impedance in the hundred of megohms, so the slightest leak gives
> trouble.
>
> An old trick with screw-in capsules is to wipe silicone grease over
> the insulators.
>
>
> > Does the circuit board have lacquer coat or not?
>
> All PCB's have a coat but for the best protection, the assembled
> circuits should be "tropicalised" over the plugs, components and
> solder joints as well.
>
> I once had a Nagra IV tape recorder swamped by sea water while filming
> open boat whaling in the Azores, and I got the batteries out within
> seconds. I stripped out all the circuit board san washed them in fresh
> water and is worked on until displaced by stereo and digital years
> later.
>
>
> > Are some sealing around capsule and XLR ends?
>
> Not around the capsule as the sound has to get in. This is the weakest
> point as the diaphragm has to be the thinnest possible. Electret
> capsues are the most vulnerable as if any damp diffuses through the
> capsule diaphragm(s), it can dischange the electret and kill the
> capsule.
>
> Plugs are often not waterproof, but are reasonable resistant to
> splashing but not immersion unless they are designed to be immersed..
>
> > Are the switches waterproof?
>
> No, unless they have a gland or sealed rubber cover. If the switch
> contacts get corroded they will give endless trounle.
>
>
> > If using isolate tape over the switches (and probably around XLR
> > too), would it be the key of trouble free recording in wet
> > conditions?
>
> Taping up plugs and switches is a good idea in wet locations but it is
> not foolproof, so take it off as soon as you are dry again.
>
>
> David
>
> David Brinicombe
> North Devon, UK
> Cogito cogito ergo cogito sum - Ambrose Bierce
>
>
>









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