Condensor Microphone Repair/Wire Layout

[reddragon105]

I have an Audio Technica ATR6550 condensor microphone that I got with a second hand camcorder about a year ago. I haven't actually used the mic in this time, but went to use it the other day and found that it doesn't work! Not able to return it at this stage, and being pretty good at fixing things, I opened it up to take a look.

I could see right away that there was a loose wire, but the inside was such a mess that I couldn't tell where it was supposed to go - the section behind the battery compartment, where the cable goes into the bottom of the mic, was full of black plastic, which I can only assume was hot glue poured in there.

So I pulled everything out of there, including a short black wire which I found embedded in the glue, cleaned it all up, and now I'm ready to put it back together - only I don't know where anything goes! I've repaired a couple of mics before, only they had XLR connectors. This one has a 3.5mm jack attached via a cable.

Here's a photo of what I've got -



Inside the mic itself are two wires, black and white, coming from the circuit board, running through the battery compartment.
There's the wire with the 3.5mm jack on one end. The end shown in the right of the photo goes into the bottom section of the mic. There's also a small piece of metal clamped around the end of the wire with a screw hole in it - it screws down onto the screw hole you can see in the end of the mic.
Then there's the spring for the negative end of the battery and a short black wire that was stuck in the glue behind it.

Does anyone have any idea where everything should go? What needs to go onto the battery spring, what needs to attach to the 3.5mm cable and what should be grounded? Or if anyone has a similar mic, would you mind taking the battery cover off and taking some pictures of the wires inside?

 

[cowboybob]

The black wire goes to the spring (battery negative termnal) as well as the black wire in the cable with the metal "retainer" clip on the end..

The white wire should go to the white wire in the same cable as above.

You'll have to carefully strip back the jacket of the cable to expose the white and black wires mentioned above.

Use shrink tubing to insulate the wires you repair.

 

[reddragon105]

Ah, I almost said 'But there's only one wire in the 3.5mm cable - it's wrapped around a plastic core', but now that I've looked closely I can see that the plastic core is actually another wire. So in this case would the inner wire be 'white' and the outer one 'black'?

 

[cowboybob]

The outer lead might be a silvery (or gray) wire "mesh" that acts as a shield and is generally the ground (or negative) connection (think the black wire). The inner, insulated (and probably white) wire is the "signal" lead.

Can't really tell from the picture, but ordinarily mike leads are arranged in thus fashion.

 

[reddragon105]

They're both copper in colour, but that could be the case.

Here's a photo, now that I've chopped a bit of the wire off and stripped it. There's a cross section of the end of the wire, and then the insides laid out with the outer wire in the foreground and the inner wire (with a bit stripped off the end) behind it -

 

[cowboybob]

OK.

Standard coaxial microphone cable.

The exterior round, braided cable is (as a rule) the ground lead (black wire in microphone case) and the central, core lead is for the microphone signal (the white wire).

Be sure to insulate the two from each other. Easiest done by "snaking" the inner core, with its insulation, out a lower, widened part of the outer braided wire.

Kind of tricky, but it can be done by removing the outer insulation only back about 1", pushing back on the braided part to "ballon" it out a little and snaking the inner part through the balloned part.

 

[reddragon105]

Thank you very much for your help! Microphone is now working, and working well, for the first time since I got it.
The main wire didn't give me too much trouble - after I stripped the outer part, the inner core was mostly already sticking out of it, so from there it was pretty easy going. Hopefully my soldering is good enough for it to last!