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Re: Re: SASS - MKH110 modification

Subject: Re: Re: SASS - MKH110 modification
From: Dan Dugan <>
Date: Fri, 11 Oct 2002 14:30:16 -0700
>I used a 4.7 uF mylar on it tonight. One on each mic. That got the
>current draw, but not the oscillation. I have a spare mic, so
>experimented with that and exchanging with one mic seemed to get it all.
>However, I then went out and recorded both with and without the MP2, and
>all recordings still have a whine at 1.73 kHz. And it's in both channels.

May be a residue of the RF in the mike beating against some clock 
(computer or dc-dc converter) in the recorder. It happens with just 
one equipment combination? Is phantom on in the MP-2? Phantom 
supplies sometimes have dc-dc converter residue in them.

>BTW, with that value cap I'm getting more low end than I know what to do
>with. I'm picking up the gas turbine power plant 3 miles away as a
>steady rumble.

Sometimes you get what you ask for...the 110 is designed for infrasound.

>I'm assuming the output transistors must still be good, otherwise I'd
>not get signal. That leaves me hunting through a whole bunch of tiny
>caps, a few resistors, and the two coils at the output end of the
>circuit board. Though it would seem the coils being bad would also stop
>the signal. The caps all seem rated at least 15 volts. It's a exercise
>in reading tiny print. The resistors are very tiny, so low wattage. I
>think they will be my first suspects. Sure wish I had a circuit diagram,
>may have to sit and make one. Only thing in common between the two mics
>is the battery, I split them off immediately. I suppose I should try
>running a 2nd battery and see if that helps.

After more experiments to discover what combinations do or don't make 
the whine, Sennheiser service should be helpful.

-Dan Dugan


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