AKG C414 XLII problem

[mihailojocic]

Hello good people!

I have problem with my C414 XLII. After plugging in there is a beautiful normal level sound for about 10-30 seconds and after starts to fade. Anything from 10-15 DB down. When goes to fade my attenuation isn't working anymore. I can also hear some kind of humming noise. I saw some similar problems and I do suspect that capacitors are bad, but as I'm not an expert (and I don't have schematic) I would appreciate help. Sending it to AKG isn't option because of a cost. :-/

I tried 2 different preamps, same. I measured phantom power. One is 47,2 other 48,4. I even cleaned membranes and dried out my everything. It was working for 5 minutes and again the same.

Help please!!!

 

[radardoug]

Its more likely to be capsule. Are you singing into it?

 

[mihailojocic]

Speak, sing, trying to record instruments. Every time is the same. I'm not really good with repairs, I know some basic stuff, but it's not going in to my head how it can be capsule. When I start mic it's really working great. Also, if it's capsule how then is possible that attenuation isn't working only when mic go into that "quiet" mode. I'm puzzled.

 

[Whoops]

If you turn it on but don't sing or talk into it, does it do the same or nothing happens?

 

[Whoops]

I also have one of those mics.

The electronic circuit is all SMD, if the problem is in the circuit it's really hard to fix or troubleshoot.
Besides some of the Lytic caps that are bigger the rest of the components are tiny.

If the problem is in the capsule at least it's easy to fix

 

[mihailojocic]

Yes, it's doing the same thing. I can hear difference in sound and when it get quiet also some kind of a humming noise.

 

[mihailojocic]

I also have one of those mics.

The electronic circuit is all SMD, if the problem is in the circuit it's really hard to fix or troubleshoot.
Besides some of the Lytic caps that are bigger the rest of the components are tiny.

If the problem is in the capsule at least it's easy to fix

Yes, you are right, but I'm lucky because one of my friends is capable to solder anything. I JUST need to figure out where to start, what can it be. I saw few similar problems here on forum, but those are different models so I have no idea which capacitors are possible problem.

For me it looks like voltage is dropping, but also have no idea where to check. As I said, I'm not really good with electronics, my knowledge is limited.

 

[Whoops]

Yes, you are right, but I'm lucky because one of my friends is capable to solder anything.\

Soldering and de-soldering in this circuit is really difficult, but maybe even more difficult is troubleshooting  the circuit and find out the fault. Without schematics even harder.

You have potentially one of these problems:

1) Bad contact or bad solder joint (works properly at start up and then when heat builds up drops connection, had that in a lot of gear, it's a possibility)
2) Bad Capsule
3) Bad component, being it Lytic Cap or any other component

I would proceed like this:

- Would try another capsule, don't need to be the same capsule just one that is compatible with this circuit from any other microphone,  and check (2) that way

- Then (1), touch all contacts with the mic working and see if the sound come to normal level. the clean all contacts and maybe re-heat all the solder joints. I do this by putting the pcb in a oven for 10 min at 95 degrees CELSIOUS. But proceed with care this can damage the pcb you have to know what you're doing. Maybe your friend if he has an hot air smd station he probably has a better method

- then (3), Replace all the bigger Lytic caps as those are easier to replace. Replace all of them with care (it has to be your friend), it's called shotgun method. It's inexpensive and easier to do than trying to figure out if any is problematic as that is really hard to do and takes a long time.
Then try the mic.
If the problem still persists probably the problem is another component, like a tantalum cap, transistor or IC, that might be harder, So leave that to the end and report back at this point. Maybe if it come to that it's better to send the mic to AKG for repair

best regards, keep in touch

 

[Whoops]

I have no idea which capacitors are possible problem.

No one knows and probably impossible to know, the problem might not even be any capacitor.
That's why it's better just to replace all of them, after you check the capsule, all the contacts and all the solder joints