saint gillis

Sennheiser MD441 lost frequencies
« on: September 15, 2019, 07:26:05 PM »
Hi I'm trying to fix this microphone.
Here's the schematic :

  Here's my problem, sometimes it sounds like a huge high pass filter, very thin voice, no low end, like those old cheap telephones.
  And then 1 hour later, it sounds good again. And then another day, big high pass filter again. I try to find a logic, to move the components inside the circuit to see if it changes something, but I can find any logic routine...
  I was suspecting the 100n capacitor, in fact I've changed them all, but it didn't help.
  Any idea?


saint gillis

Re: Sennheiser MD441 lost frequencies
« Reply #1 on: September 15, 2019, 07:28:40 PM »
I must say, when we change the switch position during the issue, the problem persists, so it couldn't be this 100n cap anyway...

Khron

Re: Sennheiser MD441 lost frequencies
« Reply #2 on: September 15, 2019, 09:02:16 PM »
Khron's Cave - Electronics - Audio - Teardowns - Mods - Repairs - Projects - Music - Rants - Shenanigans

saint gillis

Re: Sennheiser MD441 lost frequencies
« Reply #3 on: September 16, 2019, 12:15:51 AM »
Yes, so groupdiy is now the place to be to get the schematic. And BTW the cap the guy is talking about is 0.33µ, not 33µ. But the thread didn't help for my specific problem...

abbey road d enfer

Re: Sennheiser MD441 lost frequencies
« Reply #4 on: September 16, 2019, 01:49:23 AM »
I assume you might've already come across this?

https://www.gearslutz.com/board/geekslutz-forum/607724-md441-repair-help.html
Ah! Gearslutz! I can't believe how this guy is pontificating about not using phantom power on a dynamic mic without an isolation xfmr.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

pucho812

Re: Sennheiser MD441 lost frequencies
« Reply #5 on: September 16, 2019, 01:18:07 PM »
Ah! Gearslutz! I can't believe how this guy is pontificating about not using phantom power on a dynamic mic without an isolation xfmr.

from the first post of the slutz thread.
Quote
Saw an 'As-Is' non-working MD441 on ebay for too low of a price to stay away heh

Sure enough it showed up dead, no audio at the XLR, dc resistance between pins 2 and 3 showed open.

it sounds like he is surprised that it showed up dead, I guess non working as is means something else? ;D
You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is.

gyraf

Re: Sennheiser MD441 lost frequencies
« Reply #6 on: September 17, 2019, 03:06:16 AM »
..actually, "no dc resistance" is a good sign, as it points towards xlr wires broken off, not capsule discontinuity (because lowcut electronicas also shows up as dc resistance path)..

On the other hand, loosing low-end intermittently could be a bad sign, if it comes from contamination of the magnetic gap or coil assembly getting stuck/loose..
..note to self: don't let Harman run your company..

abbey road d enfer

Re: Sennheiser MD441 lost frequencies
« Reply #7 on: September 17, 2019, 03:11:53 AM »
from the first post of the slutz thread.
What do you mean? You know a properly designed balanced dynamic mic can't be harmed by phantom...?
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

saint gillis

Re: Sennheiser MD441 lost frequencies
« Reply #8 on: November 08, 2019, 04:29:54 AM »
So it looks like the problem was that the roll-off switch was dirty and was making some unwanted capacitance between the tracks. I've cleaned it and it solved the issue.
But now there is another problem, the mic works fine with a soft voice, but is distorting  with loud signals like a snare drum for instance, is that a capsule problem?

 

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