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connections to an AKG 411 capsule?

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connections to an AKG 411 capsule?

Postby chrispie » Mon Nov 26, 2012 10:41 am

Ooops! The cello player tripped over her pickup lead and it completely pulled out of the sealed enclosure, leaving only the blobs of solder behind and no way of identifying which of the two wires went where.
http://www.akg.com/site/products/powerslave,id,272,pid,272,nodeid,2,_language,EN.html
According to the service manual it is non-repairable but I'm not giving up without a try.
The problem is in deciding which of the two wires to attach where, as the identifying sleeves came out with the wires. Does it matter which way round they go?
I got inside (had to use a small saw!).
There is a very simple PCB with two connections to the capsule, one red and one white.
Opposite these there are two more connection points, from where the cable was torn.
The only component is a 'thing' between the two sides, as if on the crossbar of a capital H.
The cable in has a 'screen' that I'm 'sure' wasn't connected to the PCB, and a blue wire and a red wire.
Am I safe to assume that the red wire connects opposite the red wire from the capsule and the blue wire connects opposite the white wire of the capsule?
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Re: connections to an AKG 411 capsule?

Postby chrispie » Wed Nov 28, 2012 9:24 pm

What, nobody?
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Re: connections to an AKG 411 capsule?

Postby Hugh Robjohns » Thu Nov 29, 2012 11:03 am

I'm not entirely clear whether the cable has pulled out of the mic capsule or the power adapter XLR. However, the service documentation shows the wiring and refers to cable colours and solder contact points here:

http://www.akg.com/mediendatenbank2/psfile/datei/53/C4114055d1f49698a.pdf

Yes, it does matter which way round the wires go as the electret capsule needs DC power to drive the internal impedance converter.

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Re: connections to an AKG 411 capsule?

Postby chrispie » Thu Nov 29, 2012 3:40 pm

Thanks for looking Hugh.
Yes, I found that diagram, but it only seems to deal with the plug/power adaptor end. The cable has pulled out of the sealed mic housing, not the plug/power adapter end. Sorry my post wasn't clearer.
What I've got now that I've sawn it open is the two very,very fine wires from the capsule, red and white, attached to the tiny pcb with the capacitor on it, and two attachment points opposite. I'm assuming red to red and blue to white, but may be assuming too much, as I can't find any documents relating to the capsule itself and its connections. I was hoping someone might tell me that capsules are **always** wired to a certain colour code. Or not.
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Re: connections to an AKG 411 capsule?

Postby Hugh Robjohns » Thu Nov 29, 2012 4:20 pm

Clearly, the capsule isn't intended to be servicable, and hence no service information.

If there are only two wires to connect, one will carry the positive supply voltage as well as the audio (probably the red one), and the other will be the return, possibly doubled up with the screen.

If the capacitor is polarised then that will give a good clue where the red wire should go (the +ve end!).

If not, then you'll just have to use trial and error -- it will only work one way!

However, be aware that those fine wires often have carbon fibre strands intertwined to strengthen the cable and that makes them very difficult to solder!

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Re: connections to an AKG 411 capsule?

Postby shufflebeat » Thu Nov 29, 2012 5:33 pm

As you've had the breadknife out already, why not replace that itty bitty cable with something shotrter and more solder-able?
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Re: connections to an AKG 411 capsule?

Postby shufflebeat » Thu Nov 29, 2012 6:33 pm

shufflebeat wrote:As you've had the breadknife out already, why not replace that itty bitty cable with something shotrter and more solder-able?

...er, shorter.
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Re: connections to an AKG 411 capsule?

Postby James Perrett » Fri Nov 30, 2012 5:24 pm

The component on the board is likely to be a FET. Normally, the negative will connect to the pin of the FET that is also connected to the capsule while the positive will connect to the pin that isn't going anywhere else. You'll need a meter to work out which lead is positive and negative although red is normally positive (but don't assume that it is).

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