Altec Birdcage (639A) microphone dynamic capsule replacement

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dmp

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I have this Altec Birdcage mic that had no sound from the dynamic capsule (ribbon is working great).
The thin wires from the capsule had lost connection - trying to repair it they just kept breaking and it is shot.
I'm wondering if anyone has ideas on a replacement for the dynamic capsule?

It needs to be omni to work (the mic puts the dynamic in combination with the ribbon to get cardiod)
And the dimensions are about 34mm diameter with an allowed depth of about 20mm
 

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mjrippe

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I think it is the same element as the 633 "Saltshaker", please correct me if I am wrong, so maybe find one of those?
 

dmp

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Good to know, but those sell for quite a bit now. $400+! I would love to find a beat up 633 or 639 to use for parts but I think I might be waiting a long time.
I was just looking at a EV 635A and I might be able to get that capsule to fit.
I wish I knew of a new production mic with a decent large diaphragm capsule.
 

mjrippe

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Someone might be asking $400+ but they *sell* for considerably less.
Actually I have an Altec 660 which might work as well. It is on loan to a friend, but I don't think they use it much. If you're interested I can get it back and measure it.
 

dmp

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Actually I have an Altec 660 which might work as well. It is on loan to a friend, but I don't think they use it much. If you're interested I can get it back and measure it.
I would be interested - let me know. I never heard of the 660 but they do look similar.
I did see somewhere that the older versions (western electric) had aluminum diaphragms while the Altec labelled mics had mylar. The 639 had mylar.
 

dmp

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Here's a few pics as I started taking it apart. A transformer, an inductor, a resistor (620 ohm), a capacitor (0.12 microF)
I'm working on tracing a schematic as I've been unable to find one.
The only sketch I've seen does not show all these components. It does look original.
Piston style ribbon.
 

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mjrippe

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Interesting, looking at your earlier photo the diaphragm is silver while I recall my birdcages having the metallic blue diaphragm. Perhaps they changed over time. Anyhow, I'll see about getting that 660 back and let you know.
 

dmp

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I recall my birdcages having the metallic blue diaphragm
Interesting. This is the only one I've looked at. Now that I really look at it, I think it is metallic, not mylar.
 

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dmp

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I traced out a schematic. Haven't seen one anywhere online. The 4 wires for transformer taps come up through the base metal that seals off the dynamic chamber and were connected, then sealed in goop. Probably to connect on assembly to get the right ribbon/dynamic mix. The switching doesn't make sense to me for 'D' and 'C'?
 

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mjrippe

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Is it possible that you have R and D backwards? The three settings should be C (Combined or Cardioid) with both elements attached, D (Dynamic) only, and R (Ribbon) only.

I got my 660A back and pulled it apart. The dynamic element is bluish-silver and measures 17.5mm deep and 36mm in diameter. As mentioned by Preservation Sound (altec – Page 2 – Preservation Sound), the output is very treble-heavy. Perhaps this blends well with the darker ribbon?

In any case, it is not a special mic on it's own and mine is cosmetically rough so I would be willing to sell you the capsule to get your birdcage up and running again.
 

dmp

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That would be great. The element I pulled out measures the same so I think that is the right element. I'll send send you a PM

You might be right about the labeling.
 

mjrippe

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Here is a photo of the 660 taken apart. I re-assembled it for shipping ;)
 

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