pan60

Re: AKG D12 repair attempt...
« Reply #140 on: November 23, 2012, 01:12:40 PM »
Hey everybody,  anybody with a D12 care to confirm some measurements for me?  As close to .xxx as possible

-OD voice coil
-ID voice coil
-gap width
-confirm if coil leads are dressed 'on top' or 'under' diaphragm?
-awg magnet wire
-material: copper, alum, etc..
-# of turns per layer
-# of layers

Any dead, open coil diaphragms would help if anyone cares to donate.  If they are distorted, dented, rounded flutes, or other than perfect disregard.

LOL
we think to much alike!



Re: AKG D12 repair attempt...
« Reply #141 on: July 06, 2013, 11:34:22 AM »
Hey everybody,  anybody with a D12 care to confirm some measurements for me?  As close to .xxx as possible

-OD voice coil
-ID voice coil
-gap width
-confirm if coil leads are dressed 'on top' or 'under' diaphragm?
-awg magnet wire
-material: copper, alum, etc..
-# of turns per layer
-# of layers

Any dead, open coil diaphragms would help if anyone cares to donate.  If they are distorted, dented, rounded flutes, or other than perfect disregard.

Did you have any success in gathering this info?

dmp

Re: AKG D12 repair attempt...
« Reply #142 on: March 12, 2015, 11:00:42 AM »
Bumping this great thread - my D12e lost the low end a few weeks ago.
Used a signal generator, loosened the 6 screws in the clamping ring, and was able to slightly realign the diaphragm following the advice in this thread.
The mic is back to 100% now.
Thanks group diy

 

Re: AKG D12 repair attempt...
« Reply #143 on: March 09, 2019, 01:04:43 AM »
I have a D12 in need of repair.  I think I could gather the info I need but none of the old pictures in this thread are there anymore.  Can anyone help me out?



OneRoomStudios

Re: AKG D12 repair attempt...
« Reply #145 on: March 29, 2019, 04:08:11 PM »
I did two of these repairs recently. Both were successful - one note though. Don't just concentrate on the low frequencies when tuning the diaphragm placement. I ended having one with plenty of low-end, but missing upper-mids until I re-seat it slightly while listening to 3Khz.

s2udio

Re: AKG D12 repair attempt...
« Reply #146 on: March 30, 2019, 04:30:58 AM »
Wow, thanks OneRoomStudios for putting that link up........I have recently found the original images of the D12 strip on an old Drive. They can be zoomed for greater clarity.
I can zip them up for anyone interested, or if someone wants to host them be my guest.
10 years ago.......... really !!  :o

On the end of a Rural Twisted Pair.

stereokiller

Re: AKG D12 repair attempt...
« Reply #147 on: April 26, 2019, 09:18:23 AM »
I have a D12E which was lying disassembled since some years in a cardbox. So  i decided to try the sweep-signal-procedure. Tried three times, and still very thin. Then somewhere i read a guy who proposed to change position of the shimmer discs, means to take one disc from above the voicecoil and put it underneath the vc. I thougt strange, but gave it a try. So i plugged the mic in, took my headphones and when i grabbed the mic i already knew that something HUGE has happened. I won about 10 db's of gain and such a fat sound, i cannot believe. Now, my M88's and 441's sounds like crap compared to the D12E.
So far for my experience.
P.S. I can not really explain technically, why that happens, if someone has an explanation, i would be curious.

alhe

Re: AKG D12 repair attempt...
« Reply #148 on: April 27, 2019, 11:19:06 AM »
As someone who has repaired several old AKG's, I can confirm that changing the position of the paper shims helps in some cases. I have seen the geometry of the diaphragm change in some cases (it sinks down, pulled under by its own weight). So, moving a shim helps to lift up the voice coil. Not recommended unless something is notably wrong simply because of how fragile the wiring is. Another trick I learned is to clean the diaphragm with a small magnet (an alnico guitar pickup magnet works great) if there are any magnetic particles caught on the diaphragm.
« Last Edit: April 27, 2019, 07:59:50 PM by alhe »

chops

Re: AKG D12 repair attempt...
« Reply #149 on: April 28, 2019, 11:22:29 AM »
As someone who has repaired several old AKG's, I can confirm that changing the position of the paper shims helps in some cases. I have seen the geometry of the diaphragm change in some cases (it sinks down, pulled under by its own weight). So, moving a shim helps to lift up the voice coil. Not recommended unless something is notably wrong simply because of how fragile the wiring is. Another trick I learned is to clean the diaphragm with a small magnet (an alnico guitar pickup magnet works great) if there are any magnetic particles caught on the diaphragm.

Can you die scribe this procedure in more detail?  I’m always worried about getting pulled in by the voice coil magnet and denting/damaging the diaphragm...


alhe

Re: AKG D12 repair attempt...
« Reply #150 on: April 29, 2019, 03:54:35 AM »
I have used to lean the bar magnet against the side of the motor assembly. That way the magnet is anchored and don't slip that easily. Never damaged a diaphragm using this method but there is always a risk in doing so, so be careful.

panman

Re: AKG D12 repair attempt...
« Reply #151 on: May 01, 2019, 08:32:37 PM »
As someone who has repaired several old AKG's, I can confirm that changing the position of the paper shims helps in some cases. I have seen the geometry of the diaphragm change in some cases (it sinks down, pulled under by its own weight). So, moving a shim helps to lift up the voice coil. Not recommended unless something is notably wrong simply because of how fragile the wiring is. Another trick I learned is to clean the diaphragm with a small magnet (an alnico guitar pickup magnet works great) if there are any magnetic particles caught on the diaphragm.

First of all, the diaphragm does not "sink down,pulled under by it`s own weight". It becomes concave because of the iron dust and debris gathering around the dome. Due to the size of the magnet, it has a bigger than normal a pull and attracts the iron particles from the surroundings, but also from the mic itself, because of the corrosion. So the more debris, the more bass is lost and the more deformation is taking place and in the end the voice coil cannot move freely. A jamming voice-coil is the result.
Once that happens, it is a case for an experienced professional.

Now, if there are only a few tiny iron particles around the dome and no deforming has taken place yet, then just cleaning them away might get you the original sound back. Unfortunately, this is most likely not the case. Why? The oldest D12:s are more than 60 years old and even the reissue capsules are 22 years old already. In most cases the iron dust/debris has been gathering on top of the diaphragm for decades and was never cleaned off. And those iron particles are never spread evenly around the dome and so the deforming also never is even.  So, lifting the diaphragm higher does very seldom help. It may give you some bass back, but it won`t sound correct in the mids and highs. It will sound "honky".

Cleaning the iron debris with a magnet is too dangerous. So, that is a no go. The capsule magnet has an enormous pull and would be amplified by the magnet brought close to it. One careless slip and you can say goodbye to the diaphragm. And unfortunately only a perfect diaphragm is going to sound right. A much safer way is to use a very thin and small-tipped screwdriver, that is magnetic, because there would be a weaker pull all in all, but yet enough pull to pick each tiny particle individually away. Even then, you need to be very carefull not to let the screwdriver slip and damage the diaphragm. Actually, that should only be done by a very experienced a person, but I do not wish to discourage anybody. After all, there is no other way of learning, than doing it. After some ten or fifteen spoiled diaphragms and broken coil ends, it tends to give somewhat a better outcome.

There are much more problems, that need to be addressed, if you want to get the sound to specs.  Some of those have been mentioned in the threads here, but too many are not, because earnestly, they can only be performed by an experienced professional(with D12:s!).






12afael

Re: AKG D12 repair attempt...
« Reply #152 on: May 02, 2019, 07:14:13 AM »
I have had success taking iron particles from a mic using masking tape. I´m not saying stick the tape to the diaphragm but lift the particles with a corner of the tape.  Of course it depend of how strong the magnet is. Trying to move those particles with a screwdriver or something that will be attracted is not a good idea.

masking tape is used to clean magnet in speakers before reconing.
heavy metal is the law!!!

panman

Re: AKG D12 repair attempt...
« Reply #153 on: May 02, 2019, 05:33:54 PM »
I have had success taking iron particles from a mic using masking tape. I´m not saying stick the tape to the diaphragm but lift the particles with a corner of the tape.  Of course it depend of how strong the magnet is. Trying to move those particles with a screwdriver or something that will be attracted is not a good idea.

masking tape is used to clean magnet in speakers before reconing.

Sure you can use masking tape or even gaffa. Just, that in most cases it does not work too good for me. The iron dust often is sticking and don`t forget, that there is the magnet pull to overcome.  Now, I use the small-tipped screwdriver method, but if you read what I wrote, it should be clear, that I did not recommend it to anybody else, except a professional, who has lots of experience repairing D12-family mics. Hope its more clear now. Besides, in most cases, cleaning the diaphragm or/and lifting it higher will not bring you the original sound back. Neither will that frequency sweep do that. Much more is needed and that is skills and experience earned with years of hard work and devotion. Trying to repair a D12 is full of traps, that you need to know,
but cannot know doing it the first time. Maybe not even the following few times. So it is easy to destroy your mic beyond repair, but learning by doing is the only way, if that is what you want. Do it by all means, but be realistic about the outcome!




alhe

Re: AKG D12 repair attempt...
« Reply #154 on: May 03, 2019, 05:58:50 AM »
First of all, the diaphragm does not "sink down,pulled under by it`s own weight". It becomes concave because of the iron dust and debris gathering around the dome.

I do not disagree with you. We are essentially saying the same thing.

I think it's wise to not encourage forum members to attempt a potentially unsuccessful repair. Then again, there are not many professional techs with lots of experience on working on these old AKG’s. If you can get in touch with one locally, then great. I am only sharing my experiences as it has helped me in the past, on the assumption that people here might have some experience with working on old dynamics and fine electronics in general. I'll reinstate that it requires great care to work on old AKG’s. I have saved a handful of these if we also count the D19 and the D119, which all uses the same diaphragm.

panman

Re: AKG D12 repair attempt...
« Reply #155 on: May 06, 2019, 05:53:26 AM »
if we also count the D19 and the D119, which all uses the same diaphragm.

A little correction needs to be added here. Yes, D19C, D19E, D24 and D119 use the same transparent diaphragm, but D19B models have a differend diaphragm blue or blueish in color. Just to avoid any confusion, it needs to be added that D12 family mics do not have any of those. Well ok, as it so often is the case(with AKG), there is an exception, if we include the D17 into the D12-family. D17 also has the "same" blue diaphragm as the D19B. "Same" here too is somewhat debatable, but I`ll leave it at that, because this thread is about D12.

jordan s

Re: AKG D12 repair attempt...
« Reply #156 on: May 16, 2019, 11:08:25 PM »
I broke off the brittle leads coming off the diaphragm when I attempted to repair mine. Any way back from that?

panman

Re: AKG D12 repair attempt...
« Reply #157 on: May 17, 2019, 06:08:26 AM »
I broke off the brittle leads coming off the diaphragm when I attempted to repair mine. Any way back from that?

Yes, a very experienced expert in fixing D12:s may still be able to repair it.


 

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