s2udio

Re: AKG D12 repair attempt...
« Reply #40 on: June 28, 2009, 05:13:13 AM »
OKwill get working on posting them in the next couple of days
(Bit busy at the mo) !
On the end of a Rural Twisted Pair.


clintrubber

Re: AKG D12 repair attempt...
« Reply #41 on: June 29, 2009, 07:08:03 AM »
big thanks to keef for going where no man has gone before.

Nice for sure, but let's also not forget Roddy, IIRC he originally posted 'the mighty trick' with the signal-generator here.

Cheers,

  Peter

SSLtech

Re: AKG D12 repair attempt...
« Reply #42 on: June 29, 2009, 09:48:04 AM »
Oh, I must redirect any gratitude entirely towards Roddy. He-da-man.

Keith
"A waist is a terrible thing to mind"
Quote from: PRR
Ah, but that was 1999; we don't party like that any more.

s2udio

Re: AKG D12 repair attempt...
« Reply #43 on: June 29, 2009, 12:33:43 PM »
Hot of the press !
AKG D12E strip

Click on the pics for large zoom images.........

I have not included pics of the housing stripdown ,just the capsule (Bass chamber removed)
You will need good eyes, or a magnifier,  and most important....Patience
Here we go..............
Mark a line down the side of the capsule,...i used the two mounting holes on one side as a guide, and put a line on the top cover ,to aid orientation on reassembly.

Carefully loosen the six screws at 60deg intervals.
Remove the two screws with wire clamps attached.
NOTE......Be careful with the screwdriver at all stages as the magnet will pull it into the centre of the capsule !!
Gently Bend the sleeved lead-in wire up.....(the thin diaphram wire enters the sleeve at the bottom)
You can now remove the sleeves .....mine was free to lift off,revealing the solder joint
Remove the remaining four screws and ...........gently break any seal (if not loosened already) .......
by very gentle leavering of the cover on one side and then the other
Slowly remove the capsule cover.......mine seperated between the first and second gaskets,which left the fine wires pinned down..
another one may not.....at all stages........Be Carefull !.....Slowly does it !





You can now see the diaphram and gaskets.............one which I left attached to the cover.
There are four gaskets......two above and two below the diaphram .
The Moisture damage (Oxide) is now evident,and by gently pushing on the diaphram ..it stuck ..due to the oxide dust and dirt in the gap !
I marked the gaskets and capsule with a line to align with the body mark made earlier.
Gently remove the second gasket to free the thin diaphram wires.



Get the iron hot and re tin the joints with a small solder application, I used an extra drop of SML flux at this point to keep it clean .
While keeping the solder at melting point GENTLY tease the fine wire to the top of the lead in wire ...
I used a small plastic tiewrap end along with the iron to stroke the fine wire to the tip and finally to freedom !
Repeat for the other side





I found the best way to lift off The Diaphram ,was to delicately pinch each wire end between thumb and forefinger (two hands) and slowly lift / tease it to a safe haven !
A Deep Breath (easily blown away)
The Diaphram can now be lifted to safety .......................!!



Internals in order of dissasembly (R to L)
 


The two lower gaskets (which i numbered for reference). The bottom one was stuck firmly to the body...
Which had to be removed to facilitate cleaning of the oxide deposits from the surface.



Pull back the lead in wires from the entry holes (secured out of harms way by a tiewrap round the body).
You can see the corrosion, the oxide comes off in a white dust............



Ready for a clean !

Cleaned the oxide and rust away with a piece of scotchbrite followed by fine emery,

The all important diaphram gap was scraped with a scraper cut and shaped  from a lighting gell sheet .

Scape round and round till your wrist hurts !

Finished the gap and top with a stiff bristle (bristles cut short) paint brush.
Then a good blow out with a compessed air blower..................no damage was sustained during this process and it also cleans the small  holes that lead to the acoustic chamber

Most important......keep away from iron particles....and then
Place the body in a clean plastic bag to keep it CLEAN !!........... until ready for reassembly.





At this point I also cleaned all the other mic parts,suspension,etc......the grills were also blasted with comp air as a lot of the fibers on the inside were loose and free....
Brutal but the result was a very good proportion remained intact ....

Reassembly Time .........

Fit the fourth (or last removed) and third gaskets,using the guide marks made earlier
Using the Diaphram lift,method...... refit the diaphram........using the align mark...







To align the bottom gaskets/diaphram I delicately teased the wires into the positions as to exit the gasket near the
lead in wire holes..........when happy that diaphram looks central....... and wires are in position,
drop on the second and first gaskets
A very light touch (use small piece of thin flat plastic)  to the dome should reveal silky smooth movement.

Fit the Capsule top and fit four of the screws,(not the clamp bracket ones) tighten to pull down the top....(check the position of those wires !)
then release the tension so as to leave the top slightly loose.




Reinstate the lead- in wires and (the tricky bit) tease the diaphram wires onto the lead-ins, leaving a small bit of slack.

NOTE the diaphram wires must run up parallel with the lead-in wire,so as not to break them when replacing the sleeve and clamping .





Resolder and check for continuity ....210 ohms in my case.

Next Test and align as per Roddys procedure ( carefull with the exposed wire ends)
When its singing happily,and the screws are tensioned to feel.........tight ......but not to tight !!

Slip  the sleeves over the wire ends,......gently bend them over  (watch the diaphram wires.!!) and........
Replace the clamps and screws, tightening as per the first four





Retest with a sweep on the sig gen ...(small errors can be corrected at this stage,if all tested good the first time
 
Reassemble the mic complete and Hey Presto a full working D12 with...."Deep, stentorian bass!" quote Keef





Many thanks to Roddy for his posting of the sig sweep method ... and Keith for bringing the subject up for scrutiny

ps i will probably be editing this ...... as and when i notice anything that i might have missed ,

Hope this is of help to a few ageing D12's
« Last Edit: July 17, 2009, 06:38:39 PM by s2udio »
On the end of a Rural Twisted Pair.

SSLtech

Re: AKG D12 repair attempt...
« Reply #44 on: June 29, 2009, 02:59:44 PM »
I am humbled by the work of others.

This write-up is a work of magnificent stature! Thanks s2udio!

-Keith
"A waist is a terrible thing to mind"
Quote from: PRR
Ah, but that was 1999; we don't party like that any more.

s2udio

Re: AKG D12 repair attempt...
« Reply #45 on: June 29, 2009, 03:27:17 PM »
Thanks Keith
Glad to have a chance to contribute to this Nirvana of audio hardware information !  ;)

Regards
Paul
« Last Edit: June 29, 2009, 03:42:05 PM by s2udio »
On the end of a Rural Twisted Pair.

clintrubber

Re: AKG D12 repair attempt...
« Reply #46 on: June 29, 2009, 04:27:56 PM »
Thanks all, nice  :)

KarlH

Re: AKG D12 repair attempt...
« Reply #47 on: July 09, 2009, 12:08:30 PM »
A HUGE THANK YOU and many cases of virtual beer to Roddy, Keith and especially to Paul for the step by step tutorial!!

Due to the amount of rust and crud, I had to tear it down a la Paul (...the next time, I will not ignore the magnifying glass suggestion....) but, after a few hours and a few tense moments, I've got a proper D12!

Now to see about the 10 euro D19 from the boot sale.....

Thanks guys,

Karl

s2udio

Re: AKG D12 repair attempt...
« Reply #48 on: July 17, 2009, 06:45:51 PM »
Good to hear Karl....congrats on the repair   ;)
I just love these mics.....after my first drum session 35 yrs ago... ohh that bass drum !!

On the end of a Rural Twisted Pair.

clintrubber

Re: AKG D12 repair attempt...
« Reply #49 on: October 22, 2009, 10:40:34 AM »

Think I've found the reason why so many of these mics have the broken surround.

I mean, D12E came with a SA31-clip, which didn't gave a snug fit. So I eBayed
a SA30, as also indicated in an older D12E-doc, but &*%^$, thAts a tight fit !  :o

Can well imagine not all broken surrounds are because of dropping, but also being caused
by squeezing the mic in that tiny '30... 

My -E is still fine though, but it's certainly something I hope to keep in mind.

FWIW...


Bye,

  Peter


PS
Why nobody makes new surrounds for the D12(E) is beyond me,
a decent living could me made out of this I expect.


OneRoomStudios

Re: AKG D12 repair attempt...
« Reply #50 on: October 24, 2009, 01:22:34 AM »
Two (dumb) questions:

1. Where are you guys hooking the signal generator to the capsule? Before or after the windings?

2. Are all of you using <200Ω output impedance generators? My generator has a 600Ω output impedance so I may have to borrow one from somewhere...

s2udio

Re: AKG D12 repair attempt...
« Reply #51 on: October 24, 2009, 05:53:34 AM »
Just hook it up to the output leads of the mic........ green/blue
The output impedance dont really matter...as long as you can get it to
oscilate......I used the headphone output of my laptop with software sig gen
Just start with the output gain very low at 1khz ,and increase untill it gently sings
Then sweep from 50 to -5k listening for any nastys...
« Last Edit: October 24, 2009, 06:00:29 AM by s2udio »
On the end of a Rural Twisted Pair.

craigmorris74

Re: AKG D12 repair attempt...
« Reply #52 on: November 01, 2009, 04:03:50 PM »
Is there any chance of recovering lost bass if the diapragm has a small hole and dents?
Thanks,
Craig

Jeremy.Starseed

    Currently Sweden, oftentimes San Francisco
  • Posts: 87
Re: AKG D12 repair attempt...
« Reply #53 on: November 01, 2009, 05:21:22 PM »
Hi. I have a D12 which has two knobs on the back. Do any of you know what these do?

Mic seems to be in fair condition...but I will probably have to give it the Prodigy treatment after reading this great thread.

So, the knobs...filter, impedance...pattern select...what could it be they're meant to do?

Mothership Mastering

" You won't believe how good you sound! "

Where is that AKG D12 Disassembly/cleaning tutorial??
« Reply #54 on: November 02, 2009, 06:52:52 PM »
I saw a very detailed step by step method to take apart and clean a D12 with pics here somewhere and can't find it.  Can someone reply with the link?  Thanks, Nathan

clintrubber

Re: Where is that AKG D12 Disassembly/cleaning tutorial??
« Reply #55 on: November 02, 2009, 07:00:12 PM »
I saw a very detailed step by step method to take apart and clean a D12 with pics here somewhere and can't find it.  Can someone reply with the link?  Thanks, Nathan

Where did you search  ??? ::)

MagnetoSound

Re: AKG D12 repair attempt...
« Reply #56 on: November 03, 2009, 04:06:21 AM »

You mean the one from s2udio just a few posts up from here?
Dan

I don't think people realize what an embarrassment of riches this place is   -  Paul Gold

clintrubber

Re: AKG D12 repair attempt...
« Reply #57 on: November 03, 2009, 06:45:42 AM »

You mean the one from s2udio just a few posts up from here?


I merged the new topic asking for this thread with this thread, saved our friend a search for 'AKG + D12 + repair'.

All fine...

Re: AKG D12 repair attempt...
« Reply #58 on: November 03, 2009, 06:47:44 PM »
Yay! Success!  After I get all the flocking off the inside and the rust off the grills - is there a paint or clearcoat I could apply that will not clog the mesh to keep it from rusting again?   

Vik

Re: AKG D12 repair attempt... Further advice needed
« Reply #59 on: March 21, 2010, 12:10:17 PM »
Hi all!

Hot of the press !
AKG D12E strip
...
Hope this is of help to a few ageing D12's
Congratulations and a huge "thankyou" for creating THE best online resource on D12 repairs on the net! It certainly improved my D12, and without this thread, I would not have known where to even start with it.

I still have a question though. I'm not sure if I should be happy with the sound I'm getting now. I have reseated the diaphragm already, but when I A/B the D12 with a D112 on a bass cabinet at low volume, the D112 has *lots* more bass, making the D12 sound kind of midrangey in comparison. I've put up a sample here:

http://www.avatarzenekar.hu/files/d12_left_d112_right.mp3 

Is this how it's supposed to sound, or is there still something wrong with it?


About the mic:

It's an Echolette D12 and it appears to have been used as a vocal mic and has definitely has been dropped or whacked against something at some point in its life. The bass reflex chamber got loose and had been soldered back on. One edge of the grille is dented. The front of the grille was in a disgusting state (I soaked it in warm soapy water and eventually got the gunk out, as well as most of the fine cloth that came out with it). There is something is loose inside the capsule that rattles when I turn the mic around and the rattle gets picked up by the mic. It sounds as if a tiny piece of solder was rattling around inside. It's definitely not in the bass reflex chamber as the sound persisted when I removed the chamber and the diaphragm. I can live with it if I have to, but it would be nice to know what it is.

The bass reflex chamber does appear to have small piece of paper inside it, visible through the hole when the transformer is removed (is this normal?). It is not blocked though, I could blow through it.

I removed the diaphragm, carefully lifting it off against the tiny wires and I ran a magnetised screwdriver and some compressed air over the magnet surface to make sure there were no rust particles left in there. I reseated the diaphragm and did the sine sweep between 50 - 5000Hz. The diaphragm gives an even tone that fades in volume to just barely audible at 100Hz and below. There may be very minimal buzz at around 200Hz or thereabouts, but that could even be 'normal' for the small diaphragm.

Is it normal to have paper in the bass chamber? Any idea what could be loose inside the capsule and how to open that part up?

Thanks in advance.

Cheers,
Vik



 

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