anyone familiar with the Fairhild F/22 ?

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Doctor of Teleocity
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Syncron_3.jpg


I have been asked to mod a Fairchild F/22 Microphone ( AKA Syncron AU7A), it is the first commercially available condencer mic circa 63-64',the issues with this unit are that although It is been compared to a Neumann U87 in frequencie responce and in tone ( some what ) its a historical piece of recording equipment, produced before phantom power was available ,and depended on 2X 303448 mercury batteries ( unavailable ), for 42 volts DC, and 2X Mallory TR133 bateries for a separate 8.7 -9 volts DC .
cells1.jpg


I have been asked to mod this to accept a 48 volt Phantom and split the 48 volts to separate 8-9 volts from that, one of the main concerns is the fact that the mic has a screw lock 7 pin amphenol connector and locating the mate for it to could be challenging. then to build an XLR to 7 pin amphenol breakout cable .

I found a circuit diagram for this but am leary as it utilizes a 110K trimmer to dummy down the voltages instead of a 7809 regulater
SyncronAU7A_P48supply.png


I have the pin layout for the amphenol connector to build the adapter cable as well
this is the actual breakout cable for this unit

connect2.jpg


f22_4.jpg


does any one have expirience with this connector or know what it is called ? , I went blind looking for one earlier today starring at every thing in supplier on line catalogs .

I'm still deciding if i will accept this job or not , i dislike doing other peoples mods , they are never satisfied with the results and i dont want to reinvent the wheel .
 

studio

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I would build a breakout box.

One with its own phantom supply and separate 8volt stage with trim pot or regulate as necessary.

What's the 8.7v for?
Impedance?
 

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I would build a breakout box.

One with its own phantom supply and separate 8volt stage with trim pot or regulate as necessary.

What's the 8.7v for?
Impedance?
the circuit I show is small enough to fit in the battery compartment , the 48 volts drives the condensor the 8-9 volts drives the on board amp stage , the breakout cable takes the 7 pin amphenol and turns it into a an XLR ,
Issue here is wtf is this connector , and where do i find one , LOL
I found the site for amphenol canada just now and may fire them off an emails

2 things I need to research or figure out are ;
1)this mic uses a positive ground Jfet and the circuit requires a negative Jfet to work with the phantom power .
2) with this circuit are the other pins on the 7 pin necessary

I have the feeling I would be franken micing this unit as it is like finding the prototype broadcaster and turning it into an SG , but the mercury batteries are not available and were prone to leakage ....huge , I cleaned the inside of this unit extensively
 
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studio

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yeah, bypass those batteries if at all possible.

Connector issues. Yuck!

Just change it out to a RJ45
and be done with it! Lol.

I know, I'm no help.
 

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Doctor of Teleocity
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yeah, bypass those batteries if at all possible.

Connector issues. Yuck!

Just change it out to a RJ45
and be done with it! Lol.

I know, I'm no help.
make sure you sweep up your sunflower seed shells before you go ....LOL
 

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Doctor of Teleocity
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The 8.7 v zener is taking care of the voltage. Regulator seems like overkill if u aren’t drawing much current.
becuse the 110 K trimmer was there it threw me off as the callibration could be a little hinky and also the >10meg on the + 48 volt rail seemed like a veriable as well, the circuit seems simple enough though .

I just located the same mic on reverb with a proper powersupply to power 2 mics and one cable , I emailed this to the owner of this mic incase he was interested . it may save him a ton of greif as well as give him 2 X F/22's
 

Timbresmith1

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becuse the 110 K trimmer was there it threw me off as the callibration could be a little hinky and also the >10meg on the + 48 volt rail seemed like a veriable as well, the circuit seems simple enough though .

I just located the same mic on reverb with a proper powersupply to power 2 mics and one cable , I emailed this to the owner of this mic incase he was interested . it may save him a ton of greif as well as give him 2 X F/22's
Cool. I’m a fan of Fairchild stuff, so I’d be tempted to power through it.
 

Chud

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I have very little to contribute from a technical perspective, but that looks like a pretty cool project. I like the idea of the breakout box that @studio mentioned, but I'd be wary of modifying anything too permanently just due to the historical aspect of the mic, even the connector itself unless it's impossible to source.

***sweeps up his peanut shells from the floor as he exits*** :lol:
 

studio

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I have very little to contribute from a technical perspective, but that looks like a pretty cool project. I like the idea of the breakout box that @studio mentioned, but I'd be wary of modifying anything too permanently just due to the historical aspect of the mic, even the connector itself unless it's impossible to source.

***sweeps up his peanut shells from the floor as he exits*** :lol:
Look dude,
The reason I sit so close to the professors is so I can throw popcorn at them when they turn their back! Shoegazers!
 

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Doctor of Teleocity
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I have very little to contribute from a technical perspective, but that looks like a pretty cool project. I like the idea of the breakout box that @studio mentioned, but I'd be wary of modifying anything too permanently just due to the historical aspect of the mic, even the connector itself unless it's impossible to source.

***sweeps up his peanut shells from the floor as he exits*** :lol:
I have the same feeling , but the circuit is small enough to fit inside the battery compartment and be inocculous,
the terminals for the batteries are all spring loaded and the contacts could be made that are reversable with out issue
here is the actual inside of the mic
P1010005.JPG
P1010004.JPG

that black wire in the first photo is a an impedence jumper changes the mic from 50 to 800 ohms, but you can see there is a lot of room for a circuit board inside

( as he puts his Cheetos bag in the trash can)
 
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