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Post by mattbroiler on Sept 26, 2022 14:33:39 GMT -6
I modded an MXL 2001 with an AK67 capsule and transformer from Advanced Audio also swapped some caps and resistors in the process mic sounds much much nicer now and I am happy that it actually works still but there is a persistent busy low level static background noise that my other mics don't have I quick swapped out the input cap but that was not it that would be too easy thinking that I could continue to replace some components one at a time to try to pinpoint the issue but perhaps there is a better way to diagnose? I have a multimeter and schematic but my tech level is very beginner with regards to microphone diagnosis and repair wires and solder connections look good for the most part. I am a bit suspicious of the new transformer because the wires are kind of twisted around to reach their locations but also would rather leave it alone for the same reason.
appreciate any suggestions from the mic savvy crowd here thanks - Matt
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Post by svart on Sept 27, 2022 8:42:40 GMT -6
I modded an MXL 2001 with an AK67 capsule and transformer from Advanced Audio also swapped some caps and resistors in the process mic sounds much much nicer now and I am happy that it actually works still but there is a persistent busy low level static background noise that my other mics don't have I quick swapped out the input cap but that was not it that would be too easy thinking that I could continue to replace some components one at a time to try to pinpoint the issue but perhaps there is a better way to diagnose? I have a multimeter and schematic but my tech level is very beginner with regards to microphone diagnosis and repair wires and solder connections look good for the most part. I am a bit suspicious of the new transformer because the wires are kind of twisted around to reach their locations but also would rather leave it alone for the same reason.
appreciate any suggestions from the mic savvy crowd here thanks - Matt
Did you remove ALL of the flux and rosin from the PCB/wires/pins/etc? Flux on high impedance areas can cause noise like this. |
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Post by mattbroiler on Sept 27, 2022 9:28:04 GMT -6
I definitely cleaned the circuit boards after I was done but it's possible I could have missed something there
Looking again more closely I see one or two suspect connections that need to be redone
Trying to be logical here I am going to stick with the swap one part at a time approach and attempt to isolate that way
will make sure to clean everything thoroughly again before doing any re-testing - thanks for the suggestion
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Post by keymod on Sept 30, 2022 3:08:45 GMT -6
I had a similar problem some time after having a well-known mic person rework a C12 clone for me. It worked and sounded fantastic for a while but, after a period of storage, the noise/static issue appeared when put back into service. I put it in a plastic zip bag along with some Dessicant for a week, then thoroughly cleaned everything with 99% isopropyl alcohol and coated the hi-imp connections with a conformal coating. Did the trick, and sounds better than ever.
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Post by mattbroiler on Nov 10, 2022 4:05:28 GMT -6
thanks for the input guys much appreciated
By this time I have swapped all the parts out and back and tested in between but the noise persists. Eventually came to the same conclusion as above that I need to wrap things back up and then perform a more thorough cleaning of the boards plus do the conformal coating. Will try the dessicant trick as well that is another good idea.
Apart from the background noise issue the mic sounds really nice - hey it actually works!
I did a kit build around the same time - MicParts VP57 linear circuit kit paired with Maiku K47 capsule and that one turned out excellent - very hot nice smooth sound and no background noise
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Post by mattbroiler on Nov 20, 2022 2:21:30 GMT -6
Storing the mic in a bag with dessicant packs and repeated cleaning of the circuit boards with 99% alcohol has mostly cleared up the static noise issue - not perfect there still is some low level underlying rumble but overall the mic is much much quieter than before
Likely will repeat this process to see if things can be further improved on since it is easy to do - thanks again for the advice
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Post by keymod on Nov 20, 2022 7:44:19 GMT -6
Storing the mic in a bag with dessicant packs and repeated cleaning of the circuit boards with 99% alcohol has mostly cleared up the static noise issue - not perfect there still is some low level underlying rumble but overall the mic is much much quieter than before Likely will repeat this process to see if things can be further improved on since it is easy to do - thanks again for the advice Also try using a nonconformal coating |
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Post by mattbroiler on Nov 20, 2022 10:23:04 GMT -6
yes I have conformal coating but not familiar with non conformal?
will look that up and see what it's about
I applied the conformal coating to the high impedance connections after the cleaning process
it's really nasty stuff and I try to handle it quickly and as little as possible
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Post by keymod on Nov 20, 2022 10:56:42 GMT -6
No, you're correct. I typed the wrong thing. It is conformal
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Post by svart on Nov 21, 2022 9:24:45 GMT -6
Not to be contrarian, but I would avoid any kind of coating. The FET gate needs the absolute lowest capacitance it can possibly have and even the smallest amount of coupling through coatings can cause noise or can allow noise to ingress into the system. This is why the FET gate pin is usually suspended in the air to a teflon stand-off where the capsule lead can attach. Using a PCB mounted pin or PCB trace has problems with parasitic inductance and capacitance.
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