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Author Topic: AKG C28a (Rebadged as EMT28) With No Low End  (Read 1624 times)

Offline Timjag

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AKG C28a (Rebadged as EMT28) With No Low End
« on: January 19, 2017, 04:44:26 pm »
Any ideas? It's most definstely not the capsule - ive several of these mics so plenty of CKs of different vintages. Someone has replaced the original 3,2uf filter cap with a 1uf boring ally electro cap, but it looks quite new. All the rest look to be original components - I have a 3,3 wet tant that would fit in there nicely, I've also got a 20uf wet tant that could replace the cathode cap which seems to be original - everything else looks and measures out good. Some one suggested the tranny but that looks to meter about right and I'd assume that it would either work or not I do have a new haufe but I'd rather not replace it

Just wondered if any of you chaps would have any experiences and wisdom  before I take it apart?

« Last Edit: January 23, 2017, 03:40:04 pm by klaus »

Offline klaus

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Re: EMT28 (rebadged C28a) with no low end
« Reply #1 on: January 19, 2017, 05:53:48 pm »
It's probably not the 1µfd vs. the 3.3µfd  value that would cause extreme low end loss. I would look at the polarization cap (C1= 8nf to ground) first, and replace that with a 0.01mfd.
« Last Edit: January 19, 2017, 06:28:44 pm by klaus »
Klaus Heyne
German Masterworks®
www.GermanMasterworks.com

Offline Timjag

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Re: EMT28 (rebadged C28a) with no low end
« Reply #2 on: January 19, 2017, 07:22:49 pm »
Thanks for the quick response klaus, I'll have a look tomorrow and report back - although on the C28a it's a 4.7nf rather than an 8 which is a yellow Philips dog bone on mine - I't makes sense that it could be that maybe even  a solder break? Thanks again

Tim

Offline klaus

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Re: EMT28 (rebadged C28a) with no low end
« Reply #3 on: January 19, 2017, 08:19:08 pm »
AKG's Gesamtschaltung schematic #1525 (http://www.jlmaudio.com/C28A%20circuit.gif) shows an 8nf at that position.
But it does not matter. Anything from 5000pf on up is used in that position by most manufacturers, with Neumann choosing 10nf (= 0.01mdf or 10.000pf).
« Last Edit: January 20, 2017, 07:52:49 am by klaus »
Klaus Heyne
German Masterworks®
www.GermanMasterworks.com

Offline Timjag

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Re: EMT28 (rebadged C28a) with no low end
« Reply #4 on: January 20, 2017, 07:33:10 am »
Thanks klaus,  :)

Offline Timjag

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Re: AKG C28a (Rebadged as EMT28) With No Low End
« Reply #5 on: February 04, 2017, 01:25:01 pm »
Just to report back, the issue turned out to be an open circuit T14 on the high Z side - thought I'd mesured it but on second inspection - luckily I happened to have a T14/1 from the same era at hand. So I now have a fully functional EMT 28 :-)

Don't suppose there is anyone that rewinds T14/1s is there?

Offline klaus

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Re: AKG C28a (Rebadged as EMT28) With No Low End
« Reply #6 on: February 04, 2017, 02:54:13 pm »
Haufe still makes the T14/1 to original specs- as much as this is possible, giving modern materials.
Klaus Heyne
German Masterworks®
www.GermanMasterworks.com

Offline Timjag

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Re: AKG C28a (Rebadged as EMT28) With No Low End
« Reply #7 on: February 04, 2017, 06:30:13 pm »
Well that's strangely reassuring  :)