sE X1 Repair

M

Moses188

New member
Hi all,

Trying to repair an sE X1 which had both wires from the pcb to the diaphragm pulled off. I managed to solder them back on again but when I switch on phantom power I get a buzz that starts soft then slowly rises to a steady loud signal, not sure if it's a ground loop or not. I recorded the output with me yelling into it and underneath the buzz I can hear a faint signal coming through.

If this rings any bells I'd love to hear your ideas.

Cheers! :listeningmusic:
 
Are you sure its grounded.
Once you removed the basket to solder the diaphragm did you also remove a wire to earth from the basket?
Welcome to the forum.
Did you use low melt solder?
 
I'll try and get a decent photo that doesn't just look like a fuzzy badly lit circuit board :P

There are two leads (red one black one) and the black one solders to a point which is connected directly to pin 1 on the XLR, so unless the basket itself grounds to the bottom through direct contact or the inner bolts it should be grounded.

I just used my regular soft solder, not sure if it's low melt?

Thanks for the welcome ;)
 
Photos:
 

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Do you know for certain that the wires are meant to go there? I can't find a reference pic online.
The red wire kinda looks suspicious soldered right onto a component leg, but who knows? Maybe that's right.

The solder joints don't look the best to be honest. It could be as simple as that.
I'd check the wiring points and reflow that solder.

Was any damage done at the capsule end? It's hard to imagine pulling those wires straight off the board without doing damage at the other end.

Regarding the buzzing, I'm not sure how you're testing the mic, but it'd would need to be reassembled to eliminate any buzz.
The metal grill makes a faraday cage around the capsule and almost certainly grounds through the bolts.
In the pictures your capsule may be grounded, but the cage around it isn't.
 
sE don't release schematics or diagrams to the public, I already checked with the distributer :( Hence the guessing game.

I was reasonably certain that the red wire came off that point. Could be wrong, but as for connecting to component leg, I found that on this page (first pic, click to enlarge) ( recordinghacks .com /microphones/M-Audio/Nova )

I've soldered and unsoldered the points a few times with the same results electrically and sonically each time, so I think the points are good (if ratty looking)

I'll check the diaphragm again.
 
I've actually had signal come through it, so I'd assume that with black as direct ground that red would have to be in the right place or nothing would happen?
 
No it wasn't originally, but when I fit the two pieces together it reduces significantly however still very loud. Could it just be that the internal bolts need to be connected?
 
Right. The top half grounds fully to the bottom half when you put the whole thing back together completely. :facepalm:

Now the noise is completely gone, but signal is the same extremely quiet yelling for it to be audible level.

Still tinkering, thanks heaps for the suggestions so far! :thumbs up:
 
OK, half the battle.
You got some great info there. It's beyond my knowledge so run with that. :p

At least you know the grill has to be bolted down for proper testing now.
 
Yes and thanks HEAPS for the info you lovely people!

I swapped to a dedicated preamp for testing and I'm getting more info/better results. Now I'm hearing my voice (still quietly) with a large amount of white noise. Would there be a normal culprit for that? Not an incorrect solder point leading to the FET transistor/Q2?
 
Red looks like the right place - the end of the 1 gig resistor, and they have used a teflon stand off for good insulation.

Your soldering looks ragged. Sorry to say it but the solder needs to flow well and make a good clean mechanical joint - practice on some scrap wire if you need to.

Then you need to clean off the solder flux from around the teflon insulator using some isopropyl alcohol on a q-tip aka cotton bud. This point of the circuit is very high impedance, which means that their are comparatively few electrons to do the work. Any leakage pathways can reduce the signal and frequency respsonse, so clean off the flux.

Sounds like you got the hum sorted - the grill and body act as a Faraday cage, and shield the mic capsule and amplifier from electromagnetic interference. They should make a good connection to one another, and to pin 1 of the XLR, which will take it right back to the preamp or mixer, and from there to ground.

Hope that helps!
Stewart
Xaudia
 
Haha luckily there are two switches on the bottom part that correspond to markings on the top part. And just to make double super sure now that you mentioned it I checked both sides and it's definitely the right way around going by reduced frequency response on the back side.

The signal I am getting sounds as it should, nice and full frequency, it's just drowned in noise :/
 
Oh and both the noise and signal are still very quiet. Does that stink of bad solder?

I should stop using quick reply sorry for clutter :/
 
Moses188 said:
Could the ratty soldering be causing the white noise?
Click to expand...

Yes. That and dirt or stray flux in the high impedance area can cause noise, and loss of signal through leakage.

Problem could be elsewhere, for example a bad or mis-biased FET.
 
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