Problem with AKG K-340 electrostatic part on left side

Jan 22, 2008 at 1:55 AM Thread Starter Post #1 of 7

DaJerk

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My K340 sounded a bit dull on the left side. So I opened it and unsoldered the left dynamic driver. Guess what: no sound from the electrostatic part
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I downloaded a PDF with the circuit diagram and started to measure. Looks like the transformer is blown. Is this a common failure? And is there an easy way to test the electrostatic capsule?

If not i have to disasemble the right side and replace the capsule with the left one.

Thanks in advance...
 
Jan 22, 2008 at 2:09 AM Post #2 of 7
The transformer being *blown would be kinda unlikely since the dynamic driver would probably be damaged as well.

Look for the ultra-fine wires that come off that transformer and see whether one of them is broken.
 
Jan 22, 2008 at 2:48 AM Post #3 of 7
Hi ericj,

i have checked the wires already. But i dont measure any resistance between two of the cables. There are three of the ultra-fine cables, so i should measure something between each of them. Resoldering did not work. So i guess the transformer is blown up.

The dynamic driver is ok, after desoldering it, the left side was quiet. The sound on my Ipod was ok, not centered, a bit moved to the right, and the instruments were a little dull on the left. I must have killed my K340 20 years ago, my father used them sometimes and didnt noticed it. He gave them back to me 2 days ago.

Is it posible to test the electrostatic driver directly connected to a headamp at low volume?
 
Jan 22, 2008 at 3:19 AM Post #4 of 7
No, the electrostatic driver needs significantly higher voltages. That's why they use the step-up transformer.

You might be able to hook it up directly to a speaker amplifier. Even then it might not make much sound. We don't know what the step-up ratio of the transformer is, but most electrets are driven by hundreds of volts. A headamp or even a low-wattage speaker amp outputs tens of volts at most.
 
Jan 22, 2008 at 4:19 AM Post #5 of 7
Quote:

Originally Posted by ericj /img/forum/go_quote.gif
No, the electrostatic driver needs significantly higher voltages. That's why they use the step-up transformer.

You might be able to hook it up directly to a speaker amplifier. Even then it might not make much sound. We don't know what the step-up ratio of the transformer is, but most electrets are driven by hundreds of volts. A headamp or even a low-wattage speaker amp outputs tens of volts at most.



I hooked up a K340 electret sans transformer to my speaker amp once for some experimental purposes. From a couple feet away I could get annoyingly loud high-freq test tones out of it.

I mentioned it a few months ago, but I came up with an approximately 8:1 step-up ratio on the transformer (plus some attenuation due to the series resistor before it). I think that may have been when I was still using some crappy equipment before I had finished replacing all of my damaged test equipment though, so I should probably check it again now that my kit is back in good order.
 
Jan 22, 2008 at 4:20 AM Post #6 of 7
Ok, so i have to disasemble the other side to test the electrostatic driver. This time i will make some photos to remember the details.

I hope the defect parts are still available and not so expensive. I like the AKG and the threads about modding it. Looks like an internal rewiring job. - The print looks like "made by drunken taiwans".

Thanks for your help.
 

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