MD 421 HN switch trouble

[sr1200]

Wanted to know if anyone had any clue what the deal was with the HN version of the 421. The '5' way switch is not stepped on mine, and is kind of just like a pot, but its not even that. Theres what looks like a carbon element drum suspended between two copper blades with a lock nut on top (that the screw for the body connects to). The part that spins has a small plastic arm connected to it that fits into a notch on the selector switch. The switch does nothing. Anyone have any insight into this? The grease that was in there allowing the element to move was well broken down and felt like old petroleum jelly. I added a touch of new vasoline which made the mechanism move more freely. Wondering if it has to do with the way the internals are wired. Theres no circuit board in mine, just two leads going into the transformer, and 3 leads coming out of the transformer. The blades of this weird mechanism are connected to what seems like the input (2 lead) side of the transformer. I've long lost the serial number plate for mine, but it was well under 1000 if that makes a difference.

 

[sr1200]

Just did some NON vocal tests with something that has a little more bandwidth frequency wise. The knob IS doing something but its not a bass roll off really, its more like a volume knob. Very odd. It just kind of rolls off about 5db or so. Tone doesnt really change much.

 

[dmp]

Does it have the 'M' and 'S' on it? Stood for Music / speech, and would be intended to be a HPF (not working in your case)
Pics like this for the 421HN still show the 'M' & 'S'
I have one at home I could look at tonight. Never had it apart and wouldn't mind a disabled M / S switch at all. Why does the mic sound thin? Oh, someone turned the M S knob.

 

[panman]

Just did some NON vocal tests with something that has a little more bandwidth frequency wise. The knob IS doing something but its not a bass roll off really, its more like a volume knob. Very odd. It just kind of rolls off about 5db or so. Tone doesnt really change much.

The very old MD421s indeed had no steps in the M-S switch, but they did work the same. To test properly make sure you have it wired Low-Z(N). That is done wiring the connector in a certain way, that I need to check from my files. Does it have the full bass and proper sound in general when in the "M"-position? If not, then the MS-switch cannot do much and the problem is most likely a coil-rub or something else diaphragm related.

 

[sr1200]

The very old MD421s indeed had no steps in the M-S switch, but they did work the same. To test properly make sure you have it wired Low-Z(N). That is done wiring the connector in a certain way, that I need to check from my files. Does it have the full bass and proper sound in general when in the "M"-position? If not, then the MS-switch cannot do much and the problem is most likely a coil-rub or something else diaphragm related.

Thanks for the reply. It definitely seems to be "working" but I think you're right with the coil rub. Unfortuntely, i dont think i could even get into the body of this one, as it looks like whomever owned it before me used some kind of weird glue between the body and the metal housing. It almost doesnt look like the body can come off the housing as they seem to be REALLY intertwined... much more than the the N and U are. The inside of that cavity looks completely different.

 

[sr1200]

Does it have the 'M' and 'S' on it? Stood for Music / speech, and would be intended to be a HPF (not working in your case)
Pics like this for the 421HN still show the 'M' & 'S'
I have one at home I could look at tonight. Never had it apart and wouldn't mind a disabled M / S switch at all. Why does the mic sound thin? Oh, someone turned the M S knob.

yeah its there, its just a lot different than im used to. There may be an issue with the capsule not getting that low octave. Hope it can be salvaged.

 

[panman]

Thanks for the reply. It definitely seems to be "working" but I think you're right with the coil rub. Unfortuntely, i dont think i could even get into the body of this one, as it looks like whomever owned it before me used some kind of weird glue between the body and the metal housing. It almost doesnt look like the body can come off the housing as they seem to be REALLY intertwined... much more than the the N and U are. The inside of that cavity looks completely different.

If there is glue, then that is tough to take the capsule off. Depending on the glue, it might need some heavy solvent, but that would likely melt the plastic housing. Normally there is no glue, but you just remove the MS-switch unit and get access to the retaining-nut and remove it. Then just pull off the capsule assembly. I take it you done that already?
All that comes after that is better to be left for an expert to do, if you want a fully working mic. I is easy to do unrepairable damage, if you don`t have experience repairing these mics. But you might as well start to get your experience now and even if you fail, you`ll end up having learned something, that may help you next time.
Oh, and make sure to test with the mic wired low-Z first before doing anything else!

 

[sr1200]

 

[sr1200]

So what makes this odd to me is the glob of what feels like putty at the bottom where the wires come in. The housing and metal looks fused unlike the U and N ive worked on before. Usually the nut comes off and the body just takes a little tug and its good to go. This doesnt budge.

 

[panman]

So, there is no retaing-nut?

 

[sr1200]

 

[sr1200]

So, there is no retaing-nut?

There was i removed it already. Slightly larger than im uses to. Nut almost looks hand made.

 

[sr1200]

You can see in the last image how the body and the metal are just perfectly met where that screw comes into the barrel. Theres NO gap at all anywhere the body and plastic meet.

 

[sr1200]

The goo by the cable inlet feels like silly putty.

 

[panman]

You can see in the last image how the body and the metal are just perfectly met where that screw comes into the barrel. Theres NO gap at all anywhere the body and plastic meet.

Sorry, but I don`t understand what you mean. There should be no gap in the back there. So where is the glue? What I see is just normal. That rear is normally sealed with silicon.

 

[sr1200]

I got it!! Had to tap the screw directly with a really light hammer. There was rubber cement holding it together.

 

[sr1200]

Guess thats the end of this mic. The little coil up top is busted. Looks like someone tried to use crazy glue on it or something.

 

[sr1200]

 

[dmp]

Bummer
Looks like the body is in good shape anyway, if you ever need it. I love md421s but the body & mic clip are such crap. All three of mine are barely hanging together.

 

[panman]

The humbucking coil looks ugly, but is not broken. Otherwise you would not have gotten any signal out of the mic. That piece of cloth in the middle does not belong there. The top peace can then be glued back.