Sennheiser MKH416T repair

[Jonnie m]

PM me your address, i'll send you one.
I'm planning on selling them, populated, in the future. These are protos.
I've used them in a few of my mics.
Don't have much spare time at the mo...

Thanks MrClunk - how do I send a PM? cheers

 

[The Documentary Sound Guy]

I made an attempt at opening up the capsule over the holidays. I was unsuccessful; the capsule is very tightly sealed, and all I succeeded in doing was deforming the capsule in the vise trying to keep it steady as I cranked on it. Here's what it looks like now:

So, next step: Try to find a replacement capsule on eBay. It should be a much easier repair if I can find a working capsule! I've made an offer on one, will post updates here whether I have success or not.

 

[thespecificocean]

Hi everyone! I am attempting to disassemble a MKH 435T and I'm really struggling. I've got the set screw removed as well as the snap ring inside of the XLR jack. However, the outer tube refuses to come off the body. What am I missing here?

 

[The Documentary Sound Guy]

I haven't worked with a 435T, so you might be better off starting your own thread for that one. If it's like the 416T, what you described should be enough, and I would be inclined to guess they parts have corroded together, but you'd be better off confirming by finding a schematic or repair manual.

 

[The Documentary Sound Guy]

Also, I wonder if you are pulling on the wrong part? Again, talking about the 416T, not the 435T, but my mic doesn't come apart *through* the XLR jack; there's no reason to remove the snap ring. Rather, there's a seam in the barrel, and that is where it separates. Again, you should look at a schematic to be sure.

 

[Voyager10]

If it's like the other MKH's the pin is all you need to remove, and the chassis will "just" slide out backwards from the tube, like this:


Obviously that's not working for you, so a couple of possibilities:

• There's a felt ring at the capsule end, to keep the chassis centred in the tube, which could have got itself stuck to the tube.
• The tube might be dented or slightly bent, and it's pinching the chassis which stops it moving.

Once the pin is removed the chassis should rotate in the tube, so you may be able to loosen it by twisting before trying to pull. (Maybe plug a sacrificial XLR in, so you can grip it with pliers without damaging the mic itself?)

 

[thespecificocean]

If it's like the other MKH's the pin is all you need to remove, and the chassis will "just" slide out backwards from the tube, like this:
View attachment 122385

Obviously that's not working for you, so a couple of possibilities:

• There's a felt ring at the capsule end, to keep the chassis centred in the tube, which could have got itself stuck to the tube.
• The tube might be dented or slightly bent, and it's pinching the chassis which stops it moving.

Once the pin is removed the chassis should rotate in the tube, so you may be able to loosen it by twisting before trying to pull. (Maybe plug a sacrificial XLR in, so you can grip it with pliers without damaging the mic itself?)

Sorry for the late reply but it doesn't seem like I was getting notifications for this thread. Anyway, I did finally get it apart. I confirmed the procedure with Sennheiser, and they told me that very often it's the felt/plastic ring which solidifies or gets gummy to jam it up. That was indeed the case. What ended up working was clamping the XLR end to get more of a grip, and then simply pulling as hard as I could with a little bit of a turn. It eventually broke free, and I got it off. Whew!

As for the XLR connection, I believe that may have been part of the original issue since when I took out the snap ring, the portion of the connector with the pins essentially fell out with the wires attached. To that point, I now don't have a good reference for how it should be connected, and I don't fully understand the schematic as the pin numbers and the graphic don't match. Would you be able to take a photo of your 416T and/or advise how the connection should be made?

Many thanks!

 

[Voyager10]

Happy to oblige, it'll be a day or two as I'm away at the moment.

It's best to be sure about the wiring, as getting pins 2 and 3 swapped will likely fry the transistors in the mic, on the T power ones.

 

[Voyager10]

Here's a pic:


XLR pin 1 connects to the case but is floating from pins 2 and 3. Red / XLR pin 2 is T-Power +ve, and Blue / XLR pin 3 is T-Power -ve.

The schematics (https://groupdiy.com/threads/sennheiser.45159/) are originally in German, so rt = Rot = Red, bl = Blau = Blue, sch = Schwarz = Black.

 

[thespecificocean]

Here's a pic:
View attachment 122843

XLR pin 1 connects to the case but is floating from pins 2 and 3. Red / XLR pin 2 is T-Power +ve, and Blue / XLR pin 3 is T-Power -ve.

The schematics (https://groupdiy.com/threads/sennheiser.45159/) are originally in German, so rt = Rot = Red, bl = Blau = Blue, sch = Schwarz = Black.

Amazing! Thank you!

 

[thespecificocean]

Well I got it all back together and did some simple checks but no dice. I'm unfortunately at my limit of technical knowledge so I'll have to look around for somewhere/someone to repair it if possible. I did order another mic that is reported to be working "sometimes" so looking into that one might give me some insights. Thanks for all the tips folks!

 

[Whoops]

Do you guys know if a MKH416-T modified to work with 48V has the same specs as the MKH416 P48 version in terms of noise floor and headroom?

from the top of my mind as MKH416 P48 is powered by 48V instead of 12V, I would think it has better noise floor and headroom, am I wrong?

 

[Voyager10]

@thespecificocean (love the name) - do you have a digital multimeter and the ability to measure voltages on the board while it is powered? If so it is certainly worth checking a few DC voltages, which would give clues as to whether it is the capsule or something in the circuit. There are some posts earlier in this thread which give voltages, say if you need more information.

The service manuals are here: https://groupdiy.com/threads/sennheiser.45159/ which show the circuit layout.

 

[thespecificocean]

@thespecificocean (love the name) - do you have a digital multimeter and the ability to measure voltages on the board while it is powered? If so it is certainly worth checking a few DC voltages, which would give clues as to whether it is the capsule or something in the circuit. There are some posts earlier in this thread which give voltages, say if you need more information.

The service manuals are here: https://groupdiy.com/threads/sennheiser.45159/ which show the circuit layout.

Haha thanks! Just now getting back to this as I wanted to wait... for another 435T to compare to (Plus I always like having pairs of mics for stereo use.) Anyway, someone else had a semi-functional mic on eBay so I picked it up for relatively cheap. Has a high noise floor and getting some thumps and crackles. I tried getting the capsule off or loosened to try making a better ground connection but haven't been able to budge it. Regardless, testing the voltage between the two test points shows 5mv and it responds to adjustments on L2.

Now onto the original non-working mic. Testing the same way leads to ~3mv but does not respond at all to L2 adjustments.

Does this mean my capsule is toast? Anything else to check at the moment?

Edit - I noticed that it looked like a connection from L2 was missing so I reconnected it. Now the test results in 0mv.

 

[Voyager10]

You've posted two photos showing ~500mV and ~320mV - what were those? Those voltages are typical of a disconnected or broken capsule.

If you're seeing 0mV between A and B but it doesn't change when you adjust L2, that's suggesting a circuit problem (like the oscillator's not running or something is shorted). The first thing to check here is the voltage across C9 (i.e between the two rails which run down the sides of most of the PCB). Should be about 7V - if it's a lot higher, probably something is disconnected/open circuit. If it's lower, maybe there's a short.

 

[Tubetec]

There are minor differences between the older 416T and 416P48 capsule and associated parts , the modern capsule is interchangeable with modification of the equalisation components on the older T powered version , there is a section in the MKH service documents about this ,
My guess is both mics perform substantially the same .

Below is the schematic for the convertor board Mr Clunk kindly sent me ,
I have the parts ,but didnt put it together yet ,
I might just assemble it into an XLR barrel jack rather than trying to fit the pcb into the mic body ,
My 416T is the XLR version .

 

[Grim Reaper]

There are minor differences between the older 416T and 416P48 capsule and associated parts , the modern capsule is interchangeable with modification of the equalisation components on the older T powered version , there is a section in the MKH service documents about this ,
My guess is both mics perform substantially the same .

Below is the schematic for the convertor board Mr Clunk kindly sent me ,
I have the parts ,but didnt put it together yet ,
I might just assemble it into an XLR barrel jack rather than trying to fit the pcb into the mic body ,
My 416T is the XLR version .
View attachment 123757

Did you convert your 416T to 48V phantom?

 

[Somkereki]

I just read the comments. For many years, I repaired theater sound equipment. The most common such noise fault was caused by tantalum capacitors. If it was completely silent, I checked the quartz crystal (8MHz). Tantalum capacitors are easy to test, touch them for a few seconds with a soldering iron set to a not too hot temperature. (I use the Weller WSD-81 type, it can be adjusted between 50 and 450 Celsius) In such cases, I set it to 150 - 200 Celsius.

 

[Somkereki]

Két dolog:

Ami a recsegést és dübörgést illeti... az én 816T-m rosszabb volt, mint a hangmintád, és kiderült, hogy a kapszula rosszul csatlakozik a házhoz. Ez meglepő volt, mivel a kapszula nagyon szorosnak tűnt, és annyira fém-fém érintkezés, hogy ez tűnik a legjobb elektromos csatlakozásnak az egységben. A további megfeszítésnek nulla volt a hatása. Mégis érzékeny volt a kapszulát érő oldalirányú nyomásra. Ennek ellenőrzésére külön rövidre zártam a kapszulát az alvázhoz, és a recsegés eltűnt. Ennek "megjavításához" szerény mennyiségű Deoxit D100-at tettem egy vattapamacsra, és a kapszula és a ház közötti varrás kerülete mentén megdolgoztam, remélve, hogy a folyadék egy apró nyoma beszivároghat a kapillárisok hatására. Sikerült. Aztán a Deoxit nyomán próbáltam tovább húzni, de nem mozdult el érezhetően, de gyanítom, hogy mikroszkopikusan megcsúszott. Most már semmiképpen nem tudom recsegni. A probléma megszűnt. Csak sejtem, hogy az öntött fémváz és a megmunkált fémkapszula különbözik egymástól, és az évtizedek során elegendő páratartalom került be a kapszula-váz csatlakozás csavarmenetei mentén ahhoz, hogy félvezetőt hozzon létre.

Ami a sziszegést illeti... mivel táplálod a mikrofont? Ha a P48-at T12-vé alakítja egyetlen 12 V-os zener-diódával (ahogyan az a neten található népszerű áramkörökben megtalálható), akkor az Ön által birtokolt beépített zajinjektor lehet. Egy bizonyos feszültség (6,3V?) feletti zener-dióda láthatóan lavina üzemmódban beszorul, és proli hangforrást képez. Jobb lenne, ha négy 3V-os zener lenne sorba kapcsolva. Ezt lehetne szűréssel megszelídíteni, de nem? Nem valószínű, hogy 1000 uF-os elektrolit van egy olcsó P48-12T kereskedelemben gyártott hordóadapterben. Valószínűleg túl alacsony értékű sapka van, és ennek megfelelő impedanciája túl magas, ami eredendően hibás, mivel az adapter beszerzésének elsődleges oka a megfizethető, alacsony zajszintű régi Sennheiserek használata.

Próbaként ellenőrizze, hogy megjelenik-e a sziszegés, amikor egyszerűen csatlakoztatja a hálózati adaptert az audioláncba anélkül, hogy mikrofont csatlakoztatna. Nemrég rendeltem egy Sennheiser 12TP48 hordós adaptert az Adoramától, és amit kaptam, az egy olcsóbb PSC egység (a PSC matricával), amiről kiderült, hogy nem más, mint egy hatalmas zajforrás. Jókedvűen kicserélték ("rossz árut szállítottak"), de a csereegység még a PSC matricával is megegyezett. A nem ellenőrzött pletyka szerint a Sennheiser USA anélkül szállított PSC egységeket, hogy még átcímkézték volna őket (ez arra utal, hogy ez nem az Adorama hibája volt).

A sziszegésre az eBay-en 40 dollárért talált Sennheiser BP-2 volt a megoldásom, ami két 9V-os elemmel működik. Nem néztem meg az áramkörét, és nem is mértem, de a nevetségesen hangos sziszegés eltűnt a BP-2 becserélése után.

Ahogy írod, a Zener diódák valóban lavina üzemmódban működnek a nagyobb feszültségen. Jó minőségű RC (multi-stage) szükséges.