I fucked up ‍♂️
Last night I forgot to turn off phantom power before plugging out my interface (Audient Id24)
I had an Se Electronics Se7 plugged in (SDC)

This morning I went to use it and it was dead. It picks up a sort of noise when I touch it, and if I tighten and move the cable around sometimes it picks up an acoustic signal. It makes clicks and pops as if it were catching on and latching off from the 48v, and a low hum. I'll take it to a tech asap.

Is there any way for me to diagnose it though? I opened it up and everything looked fine and properly soldered. Any help is much appreciated

 

Hi @Manolo P, welcome to the club, you're not alone in this, you should know that!

Spoiler: Source: Grok KI

Yeah man, that’s the classic “phantom power while unplugging” killer for small-diaphragm condensers. The SE7 is a pretty budget-friendly SDC, but it’s transformerless and has no protection diodes on the output (most cheap SDCs don’t), so when you yanked the cable with 48 V still on, you basically sent a huge voltage spike straight into the FET and/or the output capacitors. That’s almost always what dies first.

The symptoms you’re describing are 100% textbook for a blown FET or a fried output capacitor:

• Picks up noise when you touch the body or move the cable → the FET gate is floating or partially damaged (acts like an antenna)
• Intermittent signal when wiggling the cable → cold/broken solder joint created by the surge, or a capacitor that’s shorting/open
• Clicks and pops like it’s “latching” on 48 V → the capsule polarizing voltage circuit is damaged (usually a resistor or zener in there gets cooked)
• Low hum → DC leakage somewhere

You already opened it and nothing looks burned or obviously broken — that’s actually normal. These parts die without visible damage.

Quick home diagnostics you can do right now (no fancy gear needed):

1. Test with a known-good cable on a different preamp/channel that definitely has phantom OFF first, then flip phantom on. If it’s still doing the same thing, it’s not your interface or cable.
2. Try a different mic (even a dynamic) on that same channel/cable of the ID24 with phantom on → rules out the interface being the problem now.
3. If you have a multimeter:
   • Measure DC voltage between pin 1 and pin 2 (and pin 1 and pin 3) with phantom on and nothing plugged in → should be ~48 V on both.
   • Then plug the dead SE7 in and measure again. If it drops to almost 0 V, something inside is shorting the phantom supply (very common when the output caps or FET die).

Realistically, 9 times out of 10 when an SE7 (or any budget SDC) gets hit like this, the FET is toast and sometimes one or both of the electrolytic caps in the output. Repair cost at a tech is usually €80–120, and a brand-new SE7 is only ~$99/£89. So most people just replace it. SE Electronics will sometimes repair under warranty if you’re polite and it’s recent, but “user fried it with phantom” is almost never covered.

If you really want to attempt a DIY fix (it’s actually not that hard on the SE7), the usual culprits are:

• Q1 (the FET) – almost always dead
• C7 and C8 (the two big electrolytic caps on the output) – one or both shorted or open

People have documented fixing exactly this on Gearspace and Reddit. You can buy replacement 2SK170 or LSK389 FETs for a few bucks and swap it in 20 minutes if you have a decent soldering iron.

But yeah… lesson learned the hard way — always kill phantom (or just power down the interface) before unplugging/plugging condensers. Sorry bro, been there with an expensive Neumann once. Feels bad.

 

You won't see a broken transistor/diode with bare eyes.

In this kind of mic is not only the quite simple electronics for the electret capsujle but it needs to bring the current down from +48V to 5 or 10 Volt by a transformer / transistors and a rectifier... These are some of parts that can be damaged.
If you're lucky, it's just a broken Zener diode in the rectifier (if you hear very low level sound (AC) from the mic), and if you can get to it, you could replace it. But that will be most likely SMD tech in a mic of this size. Very tiny parts, hard to solder.

 

Last edited: Nov 30, 2025 at 6:23 PM

Too bad you fried your mic! Fortunately (in a funny way) it'll be less expensive to buy a new one than to repair it.

 

Yes, unfortunately. Nothing gets repaired anymore. Peace to it's ashes

 

Any chance it might be a faulty cable? If it picks up noise when you touch it, cables would be my first place to look, also check if any internal wiring is touching the casing for some reason.

Also, have you tested the same setup with a differnet mic?

 

Take it to someone who knows electronic (radio amateur, guitar pedal builder, retired TV tech ...).
A simple voltage check can be enough to find a 1 dollar component to change.

But before anything else , always cross test :
Use another mic with the same cable / audio card.
And test your mic on another cable / audio card.

 

If it is the mic and not the cable or audio card, at least around me it's over 100 bucks an hour minimum.

 

I was speaking about "friendly" electronic repair
Cross check and tell us

 

The "SE Electronics SE7" currently costs €108 new at Thomann!

SE --> Support & service --> https://seelectronics.com/contact/support-service/

If you would please fill out our Support Request form, we will be able to recommend an authorized sE service center near you. However, you may be responsible for covering all or some of the repair costs if your products’ warranty has expired.

 

How about buying the insurance for it? And then… I’m not experienced in insuring musical instruments but once it saved my ass with a laptop damaged by the authorised service.
You need a proof of purchase and it must be insured in a certain period of time since a purchase was made. Good luck!

PS. Check also the contents insurance

 

Last edited: Nov 30, 2025 at 10:19 PM