AKG C414 EB problem

[balluda]

Hi, I´m having trouble with my C414 EB, it has very low output but passes sound. I´ve opened it up and checked the voltages on the DC converter card and I´m way off. Where it should be -60v , +60v , -20v I have -11v, +11v, -0,1v. I´ve got 9v at the zenerdiod like it is supposed to.

Does anyone know what voltage should be sent to the DC converter card, Voltage between the red and black wires? So I can try to locate where my problem is, if it´s the dc-converter card or something earlier in the circuit.

I read in som other thread that it could be the output transformer that´s broken, the phantom power  goes thru the transformer.
Please help!
Greetings from Stockholm.
/Jonas

 

[Pip]

I think a high impedance meter is required to read the output voltages of the DCtoDC converter as the impedance is super high in that circuit and your meter may be giving you wrong readings as its input impedance is way to low to not effect the reading. I had this problem when restoring a Sony C37 FET. It sounds like your converter may be working though.

It could be the output transformer yes I have had that happen on my 421 and that was what was going on.

Is the capsule ok? Are you seeing the phantom power to the mic properly?

There is a fabulous repair person here in Nashville area for AKG mics. Contact me if you want their name and info.

 

[Moby]

Hi, I´m having trouble with my C414 EB, it has very low output but passes sound. I´ve opened it up and checked the voltages on the DC converter card and I´m way off. Where it should be -60v , +60v , -20v I have -11v, +11v, -0,1v. I´ve got 9v at the zenerdiod like it is supposed to.

Does anyone know what voltage should be sent to the DC converter card, Voltage between the red and black wires? So I can try to locate where my problem is, if it´s the dc-converter card or something earlier in the circuit.

I read in som other thread that it could be the output transformer that´s broken, the phantom power  goes thru the transformer.
Please help!
Greetings from Stockholm.
/Jonas

You can check the dc resistance of the transformers primary windings. Try to disconnect output capacitor (C7/33uf) and measure it. Also, If C7 it's too leaky then the primary is broken

 

[balluda]

Thanks for your reply, there is something fishy going on cause when I measure where phantom connects to transformer I only get 10v between black(ground) and white or red(where i suppose i would be 48v)?

I´ve checked my phantom power and even connected an akg phantom supply that gives 49v when I measure before connecting to the microphone.

 

[Moby]

Thanks for your reply, there is something fishy going on cause when I measure where phantom connects to transformer I only get 10v between black(ground) and white or red(where i suppose i would be 48v)?

I´ve checked my phantom power and even connected an akg phantom supply that gives 49v when I measure before connecting to the microphone.

you are measuring that on open XLR? Please check the schemo. Center tap of the transformers sec goes to DC/DC thru 8k2 + 330e then to zener 9.1v

 

[balluda]

Hi, can I send 48v direct to the DC converter board and check if the DC converter card is ok?

 

[Sorr]

Back in the 1990's I had a similar fault. Turns out  it was the BAY45 diodes.