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SDC mic repair question

1 by RyanZ
I bought this non-functioning AKG perception 170 for cheap, hoping that it would be a simple fix. Am I right in assuming that white crust around the transistor is the culprit? I reached out to AKG to see if they would give me the schematic to see what part that is, but (surprise!) they won't share that info. I cannot read the part because of that crust. I can't find the schematic online in any of my searches. Does anyone have any insight into what transistor could go there?
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Re: SDC mic repair question

3 by RyanZ
Nate Dort wrote: Wed Jun 22, 2022 5:59 am Are you talking about the yellowish-whitish goo near the XLR end, at the top of the photo? That's most-likely just adhesive. I'm not sure what transistor you're referring to.
Yes, exactly. I wasn't sure if that was supposed to be there. It's very crusty like when an old AA battery leaks.Thanks!
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Re: SDC mic repair question

4 by Nate Dort
Transistors don't contain anything that would leak. I also wouldn't expect a transistor to be at that point in the circuit, right near the XLR. The main transistors in this circuit are likely the black blob near the capsule. Probably a matched pair inside a enclosure to thermally couple them. There's also some surface mount semiconductors (transistors and likely ESD protection diodes) in some SOT23 or SOT323 packages.

Basically, without tracing it out, it's hard to say what's going on. Most likely, it's the capsule, or that spring-loaded connection to the capsule. Modern electronics like this, especially semiconductors and ceramic caps, don't just fail for no reason. Capsules see a lot of abuse though.

Re: SDC mic repair question

5 by RyanZ
Nate Dort wrote: Wed Jun 22, 2022 9:29 am Transistors don't contain anything that would leak. I also wouldn't expect a transistor to be at that point in the circuit, right near the XLR. The main transistors in this circuit are likely the black blob near the capsule. Probably a matched pair inside a enclosure to thermally couple them. There's also some surface mount semiconductors (transistors and likely ESD protection diodes) in some SOT23 or SOT323 packages.

Basically, without tracing it out, it's hard to say what's going on. Most likely, it's the capsule, or that spring-loaded connection to the capsule. Modern electronics like this, especially semiconductors and ceramic caps, don't just fail for no reason. Capsules see a lot of abuse though.
Thank you. I really appreciate your response!
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Re: SDC mic repair question

7 by thecr4ne
What is the mic doing/not doing as far as non-functional? XLR and capsule are generally what see the most action and are most likely to have issues. Knowing the symptoms could help diagnose.

That white goo is very likely factory and meant to be there. Here's some guts from a 414 XLS/XL2 with an entire pc board covered with that stuff. I've seen it clear in some but it's still covered in stuff.
Image

Re: SDC mic repair question

9 by Garth
RyanZ wrote: Thu Jun 30, 2022 1:10 am Thanks for everyone's feedback. I think that I am going to take the loss on this thing. I don't see any replacement capsules out there that make financial sense to bother with. I think i will just get myself another Oktava Mk-012.
They're great mics. I could have gotten more expensive SDCs many times over along the way and figured why bother, these do exactly what I want.

Conversely I got a cheap-as-almost-free deal on one of those LDC AKG Perception mics years ago and ditched it almost immediately. It's not the same model as this but it was so bad I wouldn't ever get my hopes up about anything else in that line. Harsh and brittle AF...the usual descriptors associated w/ cheap condensers.
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