Sennheiser MD421-N Broken Roll Off Filter - Gearspace.com
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Sennheiser MD421-N Broken Roll Off Filter
Old 22nd January 2009
Here for the gear
🎧 10 years
Sennheiser MD421-N Broken Roll Off Filter

Hi all, first time poster, long time slut.

Just wondering if anyone has had any experience with a broken roll off filter on a 421? Some peanut over-rotated the filter ring on one of mine and now it doesn't stop at either of the "S" or "M" positions.

Does anyone have any experience with repairing the filter? Is it impossible/easy/ludicrous to attempt?

Old 4th June 2009
Gear Nut
root's Avatar
1 Review written
🎧 10 years
I sort of have the same problem in that my switch can over-rotate the switches and it seems that the positions don't really make a difference in sound. I called sennheiser and they told me what to do but I wondered if you have any tips in the self repair job?
Old 6th June 2009 | Show parent
Gear Nut
root's Avatar
1 Review written
🎧 10 years
Yo Do0g, Thanks for the e-mail reply.
I actually have a MD421-U5 but I think the procedure will apply to either model.
This is how I fixed mine:
A call to Sennheiser in Conn. @ 860-434****90 hooked me up w/ a tech rep who told me to take the screw out after sliding the serial# plate off and slide the switch out carefully and spray the hell out of the center whole with contact cleaner.
Because mine also slides all the way around, he also instructed me to unthread the XLR portion and slide off the actual M - - - S switch rearwards to search inside for a 1/4 inch plastic stem that probably got dislodged somehow.
BTW be careful not to lose the tiny ball bearing that's in a recessed hole in the metal barrel.
The plastic stem prevents the barrel from sliding 360 degrees around and was the reason for the switch not making the correct contact. It's the key to the whole mechanism either working or not.
I fixed mine by using tweezers to insert the tiny stem into a tiny hole located on the inside of the switch assembly.
You have to locate the hole by sliding the inside barrel around w/ a small screwdriver in order to line it up w/ ball bearing and the newly inserted stem.
Then slide the outer black switch barrel and its little hole back over the inside barrel, the ball bearing and the stem.
A pain in the ass but it worked and saved me at least a $100 not to mention my MD421 is alive and kickin'.

I hope this helps somebody,
root aka Bob G

p.s. Thanks LOADS to Dave @ Sennheiser for walking me thru this.
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