MXL V63M how to open the case

[Rick H]

My V63M after 22 years has become noisy. I suspect bad caps. I live in Honduras and ordering a kit of parts is very expensive to ship here but I can buy parts locally. My first question is: How do I open the mic case to expose the circuit board?

 

[Khron]

My V63M after 22 years has become noisy. I suspect bad caps.

What sort of noise? And why caps?

And as in 99% of cases, you unscrew the bottom bell.

 

[rock soderstrom]

Welcome Rick,

My V63M after 22 years has become noisy. I suspect bad caps. I live in Honduras and ordering a kit of parts is very expensive to ship here but I can buy parts locally. My first question is: How do I open the mic case to expose the circuit board?

Yes, describe the noises (or record them) so that we can help you better. I suspect that your microphone has problems in the high impedance area or in the microphone capsule itself due to moisture (and dust?).

 

[Rick H]

First I must learn how to open the mic. I have instructions for that now. I suspect capacitors only by hunch. With 20 years old electronics caps are the first thing to look at. While I have the mic apart I will look for dust, clean up the circuit board, look at solder joints. I am well experienced with electronics repairs but this is the first microphone I have serviced.
The noise is a low level continuous noise, but random pops which make the microphone unusable. When I leave the mic powered for several hours the pops decrease in rate and volume (as if electrolytics are re-forming). The pops are the bigger issue.
I now have the mic disassembled.

 

[Rick H]

At first visual inspection, the insides are very clean, like brand new. No visible dust.

 

[rock soderstrom]

The noise is a low level continuous noise, but random pops which make the microphone unusable. When I leave the mic powered for several hours the pops decrease in rate and volume (as if electrolytics are re-forming). The pops are the bigger issue.

the symptoms you describe match my diagnosis very well, this is not an unknown problem that you describe. I suggest you replace the capsule with another (working capsule) or install a ca. 60pF capacitor as a “dummy capsule”. If the problem is then gone, you know what is going on. An intensive cleaning of the high impedance area with 99% alcohol would also not be wrong, the impurities / moisture are usually not visible to the eye.

Sometimes it also helps to place the microphone in a dry, warm place for a some days...

 

[rock soderstrom]

I am well experienced with electronics repairs but this is the first microphone I have serviced.

The situation in condenser mics is indeed somewhat special due to the extremely high impedances (1G!). Even the slightest contamination lead to the problems you mentioned.

 

[Rick H]

the symptoms you describe match my diagnosis very well, this is not an unknown problem that you describe. I suggest you replace the capsule with another (working capsule) or install a ca. 60pF capacitor as a “dummy capsule”. If the problem is then gone, you know what is going on. An intensive cleaning of the high impedance area with 99% alcohol would also not be wrong, the impurities / moisture are usually not visible to the eye.

Sometimes it also helps to place the microphone in a dry, warm place for a some days...

Thanks for the tip. I cleaned the cartridge and exposed side of the PCB in the area of the preamp. The pops have gone away, There is some low level noise left even with the cartridge replaces with a 68 pF cap. The mic is now in a warm place overnight. I will leave it there another day.