Nady CM 90 doesn't work!

I recently took apart a Nady CM 90( MXL 603s equivalent) that was in perfect working order. I put it back together and, low and behold, it doesn't work! I tested the preamp with a Rode NT1a so, it is not a phantom power issue. Is this common? I read in another forum that someone else had the same issue with a MXL 603s but, now I can not find any info on the subject. Please help! I am getting ready to do the Royer mod on a pair of these mics and want to make sure they are in working order before any mods. Any input would be greatly appreciated, thank you.

Something simple.

Indeed! I though I read somewhere that the spring loaded mechanism that connects the capsule to the electronics is finicky. I'll try something this weekend. Happy holiday weekend to all!

Try Checking the connectivity through the case and ground. Maybe there is a small change ground isn't connected so no flow of phantom... Good idea about checking the spring, they are finicky.

No luck! I'm about ready to throw this damn thing in the garbage. I tried some things this weekend, albeit drunk, and nothing worked. I did happen to find a solder joint that is just about nonexistant from the factory. I'll throw some solder on that and see if it works. But, how could that be the case when it worked perfectly before disassembly. It was taken apart very carefully I might add. I may try alligator clips and wire to see if connectivity IS the problem. Son of a.......

I had an MXL 604 that the springy part disconnect from the PCB. Maybe the tiny hair-like wire that makes the capsule connection broke off. If you touched the FET, static discharge may have taken it out.
If I were in your shoes, I would test the capsule and output jack with the known working mic (unscrew the capsule from the mic body, and try it on the other mic first, so you don't risk breaking the working mic). If those parts work, then move forward with the Royer mod. The mod only needs those original parts in working order to make it function. I hope that helps.

-James-

HellfireStudios said:

I had an MXL 604 that the springy part disconnect from the PCB. Maybe the tiny hair-like wire that makes the capsule connection broke off. If you touched the FET, static discharge may have taken it out.
If I were in your shoes, I would test the capsule and output jack with the known working mic (unscrew the capsule from the mic body, and try it on the other mic first, so you don't risk breaking the working mic). If those parts work, then move forward with the Royer mod. The mod only needs those original parts in working order to make it function. I hope that helps.

-James-

Click to expand...

Thank you much! That indeed helps. I think the tiny wire is intact but, I have not closely inspected capsule connector. I did try another capsule on the mic but, it too did not work.There is a good chance that the FET was affected by static. I'll check those two things more closely. Thank you again as this info has been invaluable.
-Matt-

Try the broken mic's capsule on the working mic's body. If it works, you should be able to do the Royer mod (As long as the XLR connector on the broken mic is functioning properly too). None of the internal components of the original mic are needed for the Royer mod.

Stress less. Build more mics.

-James-

I have tried 3 different capsules on the mic none of which work. The only piece I am really worried about is that white plastic cone that connects the capsule to the mic circuit. I remember reading that its cone shape actually shapes the sound coming out of the back of the capsule. Without it, the mic will sound terrible which makes sense because the stock capsule is cardiod. I do have omni capsules too and I am seriously contemplating hard wiring the capsule to the electronics. Just drill out the centre and feed a wire through. Maybe a quick-connect for easy disassembly. Plus, anything has to be better than that piece of hair they call a wire in the stock version. ???

I may not have made myself clear.

-Take the capsule from the broken mic.

-Attach the broken mic's capsule to the the working microphone (it won't hurt anything).

-Check to see if the aforementioned capsule is in working order.

-If the capsule is working, re-attach it to the broken mic, and begin pulling components off the broken microphone's board to make room for the tube/valve as per the Royer mod instructions.

-Follow the Royer SDC mod instructions from here, and you should have a working mic with no capsule hardwiring required.

FWIW, The springy thing is difficult to break, and it would be very obvious if you did break it, so the chances of this being your culprit is slim. All that is needed is to make sure the parts you intend to use for the Royer mod (mic body, capsule, capsule connector, empty PCB, XLR output connector, and end cap) are working properly. Troubleshooting the other unnecessary components is an exercise in futilty.

-James-

If capsule works,

Probably very well could be the FET. I got some of the same type that are used in the u87's. Sounded really nice in some MXL condensers. Thing about replacing FETs though, you want to be able to rebias them which I kind tricky depending on the circuit.

Or you could just keep switching them out till you find one thats pretty close. Low Noise and can handle loud noises without distortion without rebias.

abechap024 said:

If capsule works,

Probably very well could be the FET. I got some of the same type that are used in the u87's. Sounded really nice in some MXL condensers. Thing about replacing FETs though, you want to be able to rebias them which I kind tricky depending on the circuit.

Or you could just keep switching them out till you find one thats pretty close. Low Noise and can handle loud noises without distortion without rebias.

Click to expand...

The Royer mod he intends to do doesn't require the electronic components originally in the mic.

-James-

Hmm Good point.

Though I should note that the mics I modded sounded pretty sweet once I replaced the caps and FEt and stuff, but anyway royer mods rock and they are good. (I already built a ton of them so I needed some fet mics )

Upon reading your first post (OP) says your getting ready to mod a pair of them? Why cant you just switch the capsule from the non working one to the new one and make sure the capsule is working? Or am I missing something. Like hellfire says, you plan or ripping out the electronics anyway...seems pointless to try and fix something your jsut going to throw out.

The capsules are in working order. I have the original pair of cardiods and a new pair of omni capsules. All four capsules are in working order. Sorry for not being more specific earlier. I was originally worried about the white plastic cone connector thing being broken. It looks difficult to duplicate. Upon closer inspection, it seems there may be an issue with the XLR jack. There is intermittent pops, that's it. So, maybe the FET is burned out. I need to test the FET to see if it is open circuit. You are correct, I am ripping out the electronic but, I did not want to go ahead and gut it not working. What I mean is, I want to mod a know working mic. I would hate to get the whole mod completed and it not work. That would make trouble shooting a real pain. Just trying to cover all bases. Thank you very much guys! You have been a real help.

The good news is that you have to replace the 3-pin XLR with a 5-pin XLR. That means, if the original XLR is faulty, the necessary new one will fix the problem. Since the Royer mod really only uses the electro-mechanical parts of the original mic, it should be easy to verify that the parts you need to complete said mod are in working order.

Take your DMM, and set it to it's ohms/continuity setting. Then, test the springy capsule connector for continuity between the tip where the capsule meets it and the very thin wire protruding from the bottom that connects to the FET. Finally, make sure there is a visible contact between the capsule and the capsule connector when the mic is assembled. If all is well, the Royer modded mic should work (seeing as the XLR is going to be changed as well).

-James-

Thank you much! I will indeed test the connector tonight. I left my DMM at my brother's house last week ( setting the bias on his tube amp). Now that have my DMM back, maybenow I can do some real testing because just visually inspecting this board is driving me crazy!  ;D

The white plastic connector tested good as well as the XLR jack. There seems to be a scratched/cut trace on the PCB. After trying to repair it to no avail, I just went ahead and tested only the components I need for the Royer2 mod. All test good. The other mic tested good also. So, I thank yous for your assistance. Your help has been invaluable.