Sennheiser MD421 Strange Noise
Old 26th March 2013
  #1
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Sennheiser MD421 Strange Noise

Old 26th March 2013
  #2
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Sounds like you did something wrong with the ground wire (shield).
Shield has to go to pin 1 of the XLR connector (assuming the connector IS an XLR...)
Old 26th March 2013
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Quote:
Originally Posted by Studerfreak View Post
Sounds like you did something wrong with the ground wire (shield).
Shield has to go to pin 1 of the XLR connector (assuming the connector IS an XLR...)
OK, so how do I determine which wire is the shield?
I read something about using a multimeter and look for 200 Ohms resistance between two wires to determine hot and cold, so the remaining wire must be the shield/ground?

Regards
leoguiders
Old 27th March 2013
  #4
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I checked the connector and measured the 200 Ohms resistance between Pin 1 and Pin 2 on the bad mic, so this seems to be the problem. On the working Mic the resistance is measured between Pin 2 and Pin 3.
Should be correct if i swap Pin 1 and Pin 3.
Is there any easy way to determine which Pin is Signal + and which is Signal - ?
Old 27th March 2013
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Quote:
Originally Posted by leoguiders View Post
I checked the connector and measured the 200 Ohms resistance between Pin 1 and Pin 2 on the bad mic, so this seems to be the problem. On the working Mic the resistance is measured between Pin 2 and Pin 3.
Should be correct if i swap Pin 1 and Pin 3.
Yes, that sounds right.

Quote:
Is there any easy way to determine which Pin is Signal + and which is Signal - ?
If you had the proper test equipment you could determine it empirically. However it would probably be easier to trace the wires from inside the microphone. Aren't the wires the same colors in both microphones?

Search Google for other discussions of 421 wiring. For example, in this very forum...
sennheiser md441 bad soldering repair?
Old 27th March 2013
  #6
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Quote:
Originally Posted by Richard Crowley View Post
Aren't the wires the same colors in both microphones?
Sadly no, they seem to be from different production years or they have been serviced at some point in time.

Quote:
Originally Posted by Richard Crowley View Post
Search Google for other discussions of 421 wiring. For example, in this very forum...
sennheiser md441 bad soldering repair?
I already did an extensive google search and I found several threads with different pin connections.

Has swapping + and - the same effect as a phase invert button? Or, in other words, when recording with these mics, can I fix it when mixing the tracks?

Thanks for your help
leoguiders
Old 27th March 2013
  #7
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Quote:
Originally Posted by leoguiders View Post
I checked the connector and measured the 200 Ohms resistance between Pin 1 and Pin 2 on the bad mic, so this seems to be the problem. On the working Mic the resistance is measured between Pin 2 and Pin 3.
Should be correct if i swap Pin 1 and Pin 3.
Is there any easy way to determine which Pin is Signal + and which is Signal - ?
Hi,
Put both mics in front of a speaker that is playing a steady tone. Match the levels of the mics and sum them together. If the signal increases, the polarity of the mics is correct. If it cancels, it's reversed. This is not something to fix in the mix every time you use these mics.
Best,
Ike
Old 27th March 2013
  #8
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Checked with my own MD421's:

There is a red wire, a blue wire and a black wire.
The black wire is the ground and goes to pin 1 of the XLR
The red wire goes to pin 3, and the blue wire goes to pin 2 of the XLR.

Sennheiser must have used different wire colors, as my other MD421 has a green wire instead of a blue wire.
In that MD421 black to pin 1
Red to pin 3
Green to pin 2

Checking the phase of the two microphones indeed is the easiest way to do with the "Ike Zimbel method".
Before changing the internal wiring of the microphone, doublecheck with another microphone.
Saves you from reversing the phase of the wrong microphone....
Quote
1
Old 27th March 2013
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Thank you so much, this was a great help!
Old 27th March 2013
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Quote:
Originally Posted by leoguiders View Post
Thank you so much, this was a great help!
Does that mean that your "noisy" MD421 is working correctly and quiet now and is in phase with your other MD421 ?
Old 30th March 2013
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Yes, it's usable now. I did not have the time to check for phase issues yet but since the red wire is connected to pin 3 in both mics I suppose they should be correct.
Old 1 Week Ago
  #12
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sorry for open an old thread again, but i have also problems with an old md421 (with bass roll off).

a friend of mine gave me one because he's not a musician and he had anyway no cable for it. but when i tried it out, it was not working, i opened it and found one cable not wired, is this normal?



https://www.dropbox.com/s/d8humdchhxrxo18/421.JPG?dl=0
Old 1 Week Ago
  #13
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Looking to the photograph it seems that the top left-hand is missing a wire.
You may see that the wire is broken off the top left pin.
Carefully cut and strip the now loose red wire and solder that to the top left connector pin.
You may clean that connector pin first so that you have a clean solder joint.

Take care !

As far as I know the RED wire goes to pin 3 and is the "- side".
The BLUE wire goes to pin 2 and is the "+ side".
The BLACK wire is the screen and goes to pin 1
(Assuming the mic connector is XLR as you did not show that on the photograph).

All of this also already could have been read when reading this thread from the start......

Last edited by Studerfreak; 1 Week Ago at 09:36 PM.. Reason: addition
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