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Author Topic: AKG D20B Connector  (Read 2820 times)

Offline Basil Mühlemann

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AKG D20B Connector
« on: October 22, 2016, 01:40:10 pm »
Hi folks
I was recently offered (!) 2 AKG D20B microphones in great condition. Unfortunately i don't have the cables for them. These mics have a special female connector, which according to Hinton Instruments was a proprietary connector by AKG called 3S17B which seems to be made from unobtanium. 

At first I thought I might be able to change the insert for a large Tuchel, but the thread is slightly smaller (M24?) so the Tuchel won't screw on.

Does anyone have an idea how to get these mics to work? If i knew how to disassemble the connector i might be able to replace it by an XLR?

Also the plastic frame around the grille has broken, what might be the best way to repair that?

Thanks in advance for any suggestions.

Offline klaus

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Re: AKG D20B Connector
« Reply #1 on: October 22, 2016, 02:15:27 pm »
A couple of pictures would enlighten us all.
Klaus Heyne
German Masterworks®
www.GermanMasterworks.com

Offline Basil Mühlemann

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Re: AKG D20B Connector
« Reply #2 on: October 22, 2016, 03:19:24 pm »
I tried to attach some pictures but it says they failed the security test?

Anyways here are some links:


Offline Timjag

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Re: AKG D20B Connector
« Reply #3 on: October 23, 2016, 11:26:12 am »
Broken plastic frame you can glue but it can be a sign that it's been dropped which is a bit of a killer for D20/12s. Flea microphones have a six pin version on the psu end of their C12 cable - I'm not sure if the make it or if it's sourced but maybe they can help, they've always been good at responding to emails.



« Last Edit: October 23, 2016, 11:28:59 am by Timjag »

Offline Timjag

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Re: AKG D20B Connector
« Reply #4 on: October 23, 2016, 12:18:40 pm »
Actually, it's not an amphenol 91-mc3f is it?



It which case the amphenol 91-mc3M is it's mate




Very similar to a tuchell - but not!

Offline Basil Mühlemann

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Re: AKG D20B Connector
« Reply #5 on: October 23, 2016, 01:18:12 pm »
Thanks for the replies so far. No its not an Amphenol 91-mc3f. The slots are rectangular like the tuchels. Its not the same as the Flea cable either, since the female connector has an outer thread. Isn't the Flea cable a regular Tuchel?

I very much doubt that the mics have been dropped. I hooked them up with just some cable stuck into the slots, and they sound nice, with no noise or other obvious signs that the mics have been mishandled. I got them from a store owner who never managed to sell them, and they where stored in a warehouse which gets pretty hot in the summer so maybe the metal grille dilated and snapped the plastic off. 

As far as gluing them, I'd like to avoid gluing the plastic to the grille, in the event I need to get to the capsule for any repairs in the future. I imagine that the 4 little holes on the bottom of the plastic frame are holes for the screws that hold the grille in place, correct? They are filled with something that looks like wax, is that to seal the resonant chamber or something?
« Last Edit: October 23, 2016, 01:20:12 pm by Basil Mühlemann »

Offline Timjag

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Re: AKG D20B Connector
« Reply #6 on: October 23, 2016, 02:13:43 pm »
I think the actual housing/grille is the same as the D12. Someone in the know once  told me the D12s were made from the capsules that didn't match up to testing - the particularly poor ones were rebranded as "realistic" brand high impedance vocal mics for RadioShack. So you could always search for a defective D12 and canablise it for parts, they've show  up on eBay  from time to time - I actually have one that died - I'm not prepaired to give up on it just yet. Not till I give it a thorough autopsy.

Not sure what the wax is but it could be the case - yes that's where the screws are on the D12. When you remove them the front and back grille will be removable then you can glue the snapped plastic back together with superglue and let it set providing you're careful you'll be ok I've done this on many a D12.

Offline Kai

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Re: AKG D20B Connector
« Reply #7 on: October 23, 2016, 06:16:36 pm »
Don't use Superglue, but 2 component epoxy glue.
I could repair my D12 this way.
It sticks to this type of plastic.
For the connnector:
It would be best to glue in a shortened XLR housing.
« Last Edit: October 23, 2016, 06:22:07 pm by Kai »

Offline Basil Mühlemann

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Re: AKG D20B Connector
« Reply #8 on: October 23, 2016, 07:02:06 pm »
Thanks for the hint about 2 component epoxy, i'll use that. When you say glue in a xlr connector, you mean in the place of the existing one? That would be my preferred method, but i haven't found out yet how to get the old one out. There is a small screw at the rear of the connector (inside the housing that houses the connector and the output transformer), but when i unscrewed that nothing came loose. If I can remove the existing connector, including that threaded outer barrel, I might be able to fit in something like this:

Offline Kai

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Re: AKG D20B Connector
« Reply #9 on: October 24, 2016, 04:34:25 am »
I haven't found out yet how to get the old one out.
You couldn't leave the original as it is and glue a shortened Switchcraft XLR (the one with the screw where the pin insert goes in from the front) into the inside of the connector tube.
Stick some fitting pins into the existing connector for contact.
Pin arrangement makes it possible to solder them directly to the XLR pins.
First stick the pins into the existing connector, solder them to the XLR insert using short hardwires to cross connections 1+3 (2 goes straight over 2), then glue the XLR housing into the tube, using the XLR insert for alignment.
Else use some short litz wire.
This way it can be reversed to original if anybody likes to do that.
« Last Edit: October 24, 2016, 05:08:39 am by Kai »

Offline Basil Mühlemann

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Re: AKG D20B Connector
« Reply #10 on: October 24, 2016, 05:10:49 am »
Well the current insert is flush with the end of the tube, so it won't be possible to insert anything in the tube without getting the current insert out. But thanks for the suggestion anyway. Or did I misunderstand something?

Offline Timjag

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Re: AKG D20B Connector
« Reply #11 on: October 24, 2016, 06:50:55 am »
Basil,

Have you tried
http://www.drefahlaudio.com/mic/1_cab.html

for connectors before you butcher the mic - having the original connector and a replacement cable. I'm sure one with turn up on ebay soon.

Offline Timjag

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Re: AKG D20B Connector
« Reply #12 on: October 24, 2016, 07:05:27 am »
Guess what!? How frustrating is that?!


http://www.ebay.com/itm/50s-60s-VINTAGE-AKG-TUCHEL-FEMALE-CABLE-3-PIN-/232122158411?hash=item360b8f0d4b:g:inkAAOSw5ZBWM-DM

you now have to find the other direction! It will happen - trust me ;-)

Offline Timjag

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Re: AKG D20B Connector
« Reply #13 on: October 24, 2016, 07:08:29 am »

Offline Kai

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Re: AKG D20B Connector
« Reply #14 on: October 24, 2016, 09:54:02 am »
Well the current insert is flush with the end of the tube, so it won't be possible to insert anything in the tube without getting the current insert out.
A shortened XLR plug might fit into the gap between housing and insert.
Of coarse the whole thing will stick out some cm.

Offline panman

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Re: AKG D20B Connector
« Reply #15 on: October 24, 2016, 10:20:19 am »
You need to remove the top of the casing and looking inside you see, that the connector is threaded and a ring with slots on both sides tightens it on place. Loosen that ring and you can remove the connector. You need to desolder the wires of course. Sounds easy, but it ain`t. The copper wires are frail and snap most likely.

The bass roll-off coils are made of particularly soft copper and tend to break and then you need to replace the coils. Then just find a fitting XLR with a proper thread.

The plastic frame is just one of those lousy "improvements" done to save expenses I guess. It just tends to brake and no glueing would hold forever. A thick layer of epoxy is likely to hold, but how does it look like. I have had best results soldering with similar plastic and sinking in three metal pins to strengthen the joint. Afterwards I try to make it look as original as I can. Not easy though, but with a lot of practice....

Lots of stories around about the D12, D20 capsules. I have never found any proof of any significant difference in the quality. In the fifties mostly(always some exceptions)D12 and D20 used the same capsules, but then coming to the sixties the D20 and D25 had the whitish "paper"-diaphragm, whereas D12 had a transparent diaphragm and that in many variations too.

Always variations too many to even start with, but the basic sound-properties remained within tight enough limits. One important detail is, that D20 and D25 always had 60-ohms capsule. D12 had either 60 or 200 ohms. To alter the output-impedance a transformer was used or not.

Did not mean to fill the thread, so I leave it at that.


.
« Last Edit: October 24, 2016, 11:17:59 am by klaus »
Esa Tervala

Offline Basil Mühlemann

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Re: AKG D20B Connector
« Reply #16 on: October 24, 2016, 12:40:35 pm »
Wow I guess the collectors have now discovered vintage connectors as their new playing fields  :(
Thank you for finding these offers on ebay but fitting an xlr will be more practical and a lot cheaper. This ain't butchering the mic in my view, even though it might lessen the resale value. I plan to use these mics, not exposing them in a museum. And btw it would still be possible to restore it to its original condition by refitting the old connector.

Panman, many thanks, that was exactly the information I needed!

Offline Kai

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Re: AKG D20B Connector
« Reply #17 on: October 24, 2016, 01:01:13 pm »
The plastic ... no glueing would hold forever ... best results soldering with similar plastic and sinking in three metal pins to strengthen the joint. Afterwards I try to make it look as original as I can. Not easy though, but with a lot of practice....
I've restored a lot of broken plastic parts using this method, but:
Do it from the inside and cool the outside by using a dripping wet piece of cloth, while melting the plastic.
This way the visible parts will not deform.
You need a temperature controlled soldering iron with a broad flat tip, at a temperature of about 260 °C.
Melting in some metal parts is necessary to strengthen the joint.
Very small screws are best, or even pieces of paperclips work well if you raw their surface and / or bend the ends into little hooks.
« Last Edit: October 24, 2016, 01:04:07 pm by Kai »

Offline Basil Mühlemann

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Re: AKG D20B Connector
« Reply #18 on: October 24, 2016, 01:22:32 pm »
Great idea doing it from the inside, Kai. Thanks!

Offline panman

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Re: AKG D20B Connector
« Reply #19 on: October 24, 2016, 03:54:36 pm »
Do it from the inside and cool the outside by using a dripping wet piece of cloth, while melting the plastic.
This way the visible parts will not deform.

I don`t see how this would work in this case. To make it hold you need to melt both sides. Any crack left on the surface is a weakness and breaks again from there.
Or did you mean while melting the other side, cool the outside and yet do both sides?
Esa Tervala

Offline Kai

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Re: AKG D20B Connector
« Reply #20 on: October 24, 2016, 07:35:20 pm »
You just do the inside.
The metal inlays prevent it from breaking again.
I did that very often, it works.
This way you preserve the looks of the visible parts.

Offline panman

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Re: AKG D20B Connector
« Reply #21 on: October 25, 2016, 07:24:22 am »
Ok, am going to try that next time :).
Esa Tervala