How does one take a Sennheiser MD 421 apart?

Question edited for clarity, full 'make model (what it is)'.
Question moved to a better category.

Definitely worth repairing. You can also get repair kits.

https://www.google.com/search?q=Sennheiser+MD+46+repair

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This would require a special cable to work. The mic is MONOAURAL with BALANCED output and the camera is STEREO input. This means a special cable is needed and you would probably have to make it yourself as I haven't seen one on the market.Pin 2 of the XLR of the mic would go to BOTH the tip and ring of the plug into the camera. Both pins 1 and 3 of the XLR at the mic would tie to the sleeve of the plug to the camera. If you tried an XLR to 1/8 adapter, no audio would be heard other than from the buillt in mic.

Check the cable. It maybe damaged. Check your phantom power. If your going to yell into the mic...Turn the input gain down to avoid initial distortion. Not sure of your recording setup, but everything in the chain input to output is key.
You can probably assume the mic to be damaged if these things dont check out.
I have a MD 421.

Sounds like the membrane hooks on to something at high SPL's. And perhaps especially at low/low-mid frequencies. You most probably need them taken apart and have them examined.
That 5 of 8 has gone bad makes me believe it related to something that weaken with time. Say, foam going dry, tape losing its grip, rubber going stiff.
Could be an easy mechanical fix, but yes, one would have to take them apart and examine them closely.
I would ask for a service quote directly from sennheiser. They are lovely mics, and may well be worth the effort.

No, just the high-pass filter sleeve.
Sorry, Cody J.

download the manuals on the website of your MKE-300

Hi,

It could be a dirty switch, you can find this switch at the back of the 421. You can rotate it several times to clean the contacts a little bit. Otherwise you have to take the 421 apart.

Good luck,
Gerard

Well, it looks like an SKM 100/g2 casing so if that is true, then unscrew the bottom part till you have access to the batteries and there are three star screws you'll need to take out right between the battery compartment and the bottom with the LCD screen. The bottom cover slides down and off. If you need the cartridge out then you unscrew the top of the mic where the actual pickup is and pull the core out through the top. That should be close, but might vary a little bit.

Hi,

First you must loosin the connector.
There's a little shield with the serialnumber you can slide away.
Underneath that you will find the screw to loosin the connector/filter.
If you look inside you will find a bolt, unscrew that one and the element will seperate from the housing.
Thats what I remember after 25 years.

Good luck,
Gerard

There are different frequencies available and being used in each location.

To get a basic idea of which frequencies are available in your area, try this online tool:
http://www.sennheiserusa.com/findfrequency/
or use the literature provided with the Sennheiser gear (usually a useful chart comes with the wireless gear).

Also, remember that your transmitting frequencies need to be spaced apart a minimum of .400 MHz (or 400 kHz).

Frequency selection shouldn't cause feedback problems though. If you select a frequency for a mic that a local TV station is already using to broadcast, it will cause RF Interference (Radio Frequency). You'll probably hear static noises, pops, or since your Sennheiser has a Squelch feature, just drop-outs in audio.

So first consult the available charts to find a set of frequencies that should be available in your area. Then, if one of your mics is experiencing such an issue, try moving it .400 MHz to the nearest unused frequency and see if the RFI goes away. Repeat until the RFI no longer manifests.