Slightly ill MD441

[MicDaddy]

Ha, that's exactly how I have found broken PCBs.  I've found that capacitor is completely broken physically in the ones I've played with.

Send an email to Senn....  request schematic for PCB.  I was lucky enough they just sent me a replacement at no cost.  I'm sure once word gets out about this they may not be so apt to shoot off filter boards for free, but worth a shot.

Very gently push down on the center dome of the diaphragm.  What you need to watch for is good movement, or bounce all around the coil.  If the coil appears to go down/up concentric with the rest of the diaphragm then the diaphragm most likely is going to function. 

You might try hitting the voice coil leads with a very small DC ~.5-1.5VDC.  The diaphragm will jump up or suck down.  If it sucks down, swap the polarity of your DC leads.  Once you get the diaphragm to jump up, look around the edge for any air leak.  If it doesn't get a good bounce, or jump up, you might try to re-flow the solder at the terminals where the voice coil leads terminate.  After this if it still doesn't bounce well, it most likely needs a new coil/diaphragm assembly.  If you can get Senn to send/sale you one let me know so I can stop reversing this design.

That dent very well may be putting stress on the flutes causing the excursion to not be optimal.  What you can try, doesn't always work, is take some masking or other adhesive tape that will not leave residue, and roll it up like you're going to use to put up a poster.  Now pinch it to get an adhesive point, now take this point and carefully press on your dent.  Use the adhesive with a pulling action to try to pull the dent out.  You might also try the blue tacky poster sticky stuff if tape won't grab it.

Do be careful, I've found that the flute area of these diaphragms is almost paper like and very very soft/fragile. 

I'd also try to hit the coil leads with a low level signal from a sine generator.  The element should act like a speaker and reproduce the signal.  If no tone, something is wrong.  If you get tone take the frequency generated to ~30Hz.  You can observe the diaphragm bounce at full excursion up and down and note for any sticking or rubbing.  Even as low as 10Hz will allow for the diaphragm to bounce very slowly, enough to observe the movement very well.

 

[mindlessstudio]

Thanks, will try all of that later on today and get back to you. I actually already tried contaction Sennheiser per mail, but they don't reply. If you've got a contact there would you mind sharing their email address?

The PCB doesn't seem to be terminally wounded though. I think I might be able to fix it with some additional wiring and a bit of clue, as far as I can tell no components have been ruined by the break. Fingers crossed – but I do have a nasty hunch that the coil diaphragm assembly needs to be replaced.

Back later, need to go do some family stuff now

 

[ln76d]

If you want to contact sennheiser service, try to German not your local.
In case of pcb - if you have all of the broken parts, you can fix it.
Just use "super glue", to join them. If the glue will dry, you need to scratch solder mask from broken copper traces.
Then you need to put solder tin on them and join them using bare wire - solid core, not so thick. Some people use for this very thin kynar wires.
You should think about replacing all tantalum capacitors.
In case of diaphragm. First look on solder pads, if there are very thin voice coil leads properly soldered.
In case this little dent, i have few of them on e609/906 diaphragms which they looks very similar.
My method was maybe not so professional but it always works.
Maybe it will sounds stupid - but i've used my mouth to do that
A gently suck with the air  ;D ;D ;D ;D
Sometimes capsules have holes on the back and you can gently blow the air to the inside.
This diaphragm is probably very flexible, so ti should works at the first time.
You should think about replacing all tantalum capacitors.
I hope it's understandable i have no head today to write in foreign language

 

[1elwoodblues]

Using the info in this thread and another similar one from about a year ago gave me the path to repairing my old 441 which fell on the floor some years ago. I sent it to a "pro" but they couldn't fix it. It was as in the "441 Repair Help" Thread from a year ago. The circuit board cracked in the same spot. I was able to repair it & get it back together and it works again! I wasn't planning to pay Sennheiser for a new cartridge assembly, so I figured I'd take a chande and give it a try. Thanks all for the information!

 

[beatnik]

Time for me to revive this thread

I have picked a defective MD441 hoping to restore to its former glory

The mic had a low output and lacked in bass response

By looking at all the info available on the forum I took it apart and did the test by connecting the cable straight to the coil wires

Even this way I still have the same weak sound

I was hoping the problem to be in the filter circuit, but now I guess there is some damage in the capsule

Is there anything I can try to fix it?

 

[beatnik]

Another thing I found is the foam on top of the capsule was very deteriorated and there are a lot of particles all over the place.

I have read that the foam can stuck into the diaphragm and making the mic sound weird

What do you think?

 

[MicDaddy]

I think if you haven't already it's now time to look at the diaphragm.  Careful, the flute area is very soft while the center dome is quite stiff.  Think of like silky tissue paper, this is what the flute area reminds me of.  You might have a lot of debris on the diaphragm limiting it's overall output and sucking up all the low end.

The resonator (black plastic thing on top of the mic head) needs to be removed, careful not to severe lead wires as they lie right underneath.  If the resonator doesn't come off freely, I'd try low low low low stupid low heat, maybe even friction from hand and fast movement as if trying to start a fire with rubbing sticks.  Too high heat and you might cook the diaphragm, but enough direct heat might allow for the resonator to be removed easy enough.  I wouldn't even think about solvents here.

Carefully clean the diaphragm and try again.  Even throw on headphones and listen real time as you clean and you might hear it come back  8)  just keep the volume down cause it's not the most pleasant noises.   

Another thing I found is the foam on top of the capsule was very deteriorated and there are a lot of particles all over the place.

I have read that the foam can stuck into the diaphragm and making the mic sound weird

What do you think?

 

[beatnik]

Thanks for coming to help

I have done one step ahead and as you suggested i took the resonator off and got access to the diaphragm

There wasn't any foam particles on the diaphragm but i cleaned anyway with alcohol and a q tip and i realized it had a layer of paint or something. white color

Now that I've cleaned it is crystal clear.

I have put back the resonator and hook up the mic cable to the coil wires, but I haven't noticed any improvement in sound, still very lo output and no bass

any suggestion on what to do next? i'm completely lost

 

[beatnik]

by the way, i am doing the test by wiring pins 2 and 3 of the xlr cable straight to the two coil wires. can you confirm this is right?

 

[MicDaddy]

Yes you should be able to run the voice coils out to the XLR. 

The layer of paint could possibly have been for dampening, but that's just a guess.  I have seen painted/dampened diaphragms.

It could have an air leak, the coil could be coming apart, there could be a small tear or place near the outer edge of the diaphragm where there's not a good seal.

Sorry I don't have any better leads for you.  Do you get a nice bounce if injecting a lower frequency ~ <10Hz

 

[beatnik]

there could be a small tear or place near the outer edge of the diaphragm where there's not a good seal.

should i try glueing the outer edge of the diaphragm?

Do you get a nice bounce if injecting a lower frequency ~ <10Hz

How i do that?

 

[MicDaddy]

should i try glueing the outer edge of the diaphragm?

Only if you can verify a leak somewhere.

How i do that?

Hook it up like a speaker, positive to pin2 neg to 3.  Don't blast it apply just a small level from a sine generator.

 

[beatnik]

can i use the daw? what level in dbFS?

 

[panman]

Look, before you do anything, try if the diaphragm moves freely! You can do that by pressing carefully the dome down. It should not have any resistance and bounce back easily. That white color should be there and certainly had nothing to do with loosing the bass. Either the  coil is jamming or the diaphragm is damaged or it got loose. Any dent or fold or indention take the bass away. There may also be iron particles around the dome pushing down, because themagnet pulls them. They do not go away with alcohol and tip. Sorry, but your mic will not profit from more repair-attemps by you.  It`s ajob for an expert.

 

[MicDaddy]

can i use the daw? what level in dbFS?

Yes, think low headphone level, whatever that is dBFS.

0dBu should be ok

Any dent or fold or indention take the bass away. There may also be iron particles around the dome pushing down,

 

This is why I like to suggest to pump some low end up the back side.  This way you can still observe full excursion, slow enough to witness the bounce, without having to physically push on in down the diaphragm. 

Though I will use a finger to manually bounce when centering.  On a thinner diaphragm the risk of creating a dent or crease is higher.  The MD 441 diaphragm is not very stiff, it should give pretty easily if you do push on it, just don't press very hard.  More of a tap tap on the dead center than a push, it should bounce right back up if it's ok.  If around any edge of the coil area it's stuck or slow to recover, it probably needs a new coil or re-centered or some other invasive procedure. 

 

[Aref]

Hey all,
This is my first post here, really great place to learn things.
I bought few non-working condition MD441 and could get a sound from two of them with just bypassing the brillance filter.
I detached the coil wires and used another wire from there through suspensions to the bass filter. Do I have to keep the coil (Maybe the hum compensation coil) in the circuit?

How do you clean in/outside of the diaphragm? What about the magnet?
I found a diaphragm in a good shape (far left) and trying to find the best match among these three for it....any idea?

 

[Aref]

Another view..

 

[micaddict]

Welcome! 

 

[Aref]

What kind of glue should I use for that paper around the magnet?

 

[Aref]

Any help?