Neumann Vintage U87 Clone : Build Thread.

[Matt55]

I though them photos would just show up on the fourm like other photos but it seems they do not. They are still viewable on dropbox but means an extra click.

When you say FD can I ask what you mean?

Thank you,

  Matt

 

[Krumlee]

Hi Matt,
Thanks for the pics. I can't see anything obviously wrong. Your construction is definitely neat and tidy. Did you inspect all the solder joints really carefully? A couple of the joints under C1 & C17 look like they could use a little more solder, though it's hard to tell just looking at pics. Get a hand magnifier and a really good light and look at every one very carefully. Even the best people occasionally make a bad joint. Remake any that you're not 100% sure of.

When you've done that, measure and post your dc voltages (Zener, R14, Fet (drain and source) and capsule (measure it at FBK))

 

[tskguy]

do you mind posting some pics of how the capsule is wired??

 

[Matt55]

Hey Eric and Krumlee,

Again thanks for the patience and help I am a bit useless when it comes to solving problems like this.

So I took the voltage measurements and they are as follows;

Zener: Right  23.1v
            : Left    0v

R14:  21.1v

Fet: Drain    11.6v
      : Source  3.0v

Capsule: FBK -  33.0v (Measured the same in all modes, Cardiod, Omni and Fig8)

Now what was funny was that RBK measured only 6v in Cariod and then 6v in Omni, but 0.2v in Fig 8. Does that sound right, I would have thought in Fig 8 both sides of the capsule would be getting the same power??


Eric;

With regards to capsule wiring, the front Diagphram wire goes to FD, the front Backplate wire goes to FBK. The same for the rear capsule connections. I attached the wires for the backplates using the mouting pisitions in the saddle using the screws you provided to hold the capsule in place which is what I though you said I should do in the email, I may have mis-interpreted this though... The wires are 100% making full continuity with the correct backplate and there is no cross talk. I wired up my U47FET exactly the same way.

I have just finished my U47FET and it seems to work (no noise just pure signal). I am doing a vocal test with it in a bit and will let you know my thoughts

Thanks for the continued help guys

Regards,

  Matt

 

[poctop]

Capsule: FBK -  33.0v (Measured the same in all modes, Cardiod, Omni and Fig8)

Now what was funny was that RBK measured only 6v in Cariod and then 6v in Omni, but 0.2v in Fig 8. Does that sound right, I would have thought in Fig 8 both sides of the capsule would be getting the same power??

you cannot measure polarisation Voltage direclty this way , the High impedance will thorw your meter off ,.
what you have to do to assess logical polarisation is to measure the voltage before the High imedance Resistor ,
Best,
Dan,

 

[Matt55]

Hi Dany,

Ok, I didnt know that. Maybe you can suggest where I should be measuring instead?

I guess the measurements I gave above are in accordance with the schematic and what they should be reading?

Regards,

  Matt

 

[Krumlee]

Matt,
You'll only see the capsule voltages shown on the schematic if you use a special type of meter. But you're seeing enough to polarise the front of the capsule.

The next thing I'd test would be to see if you can get some audio through the mic.
- Unsolder the FD capsule wire from the pcb
- Get an audio signal from somewhere eg the headphone output of an mp3 player, or anything else with simple headphone jack out. Improvise a cable to connect it to the mic as follows:  Connect the headphone jack 'sleeve' to the mic ground, and the 'tip' to point FD on the pcb
- Power the mic up with phantom power and monitor the output. You should hear the input signal clear and undisorted (as long as the input's not too loud). And probably some mains hum too, but don't worry about that.
- If you can't hear any signal, then try applying the input (tip connection) directly to the fet gate.

If you can hear the audio when it's applied to FD then it may be a capsule wiring problem. It would be useful if you could post a couple pics with the headbasket removed.

I'm going away at the weekend for about two weeks, and I'll be out of internet range. Hopefully someone else can jump in and offer assistance if I'm not around. But don't distract Dan if he's working on those capsules 

 

[Matt55]

Hey Guys,

Still no luck with my D-U87 mic.

I haven't tried to disconnect the capsule wiring yet because I thought that maybe I have wired it up incorrectly as per a few comments on here so I have uploaded some pictures of how I have it currently wired;

Note; I Installed the capsule wearing gloves, and only removed it from its box to install it. I then put the basket on and used a clear plastic component bag around the headbasket secured with tape to prevent any dust or anything getting in there.

Picutres;


https://www.dropbox.com/s/ic7fr3do9m33tps/Pic%206.JPG?dl=0

https://www.dropbox.com/s/pzw7nham6zffwff/Pic%207.JPG?dl=0

https://www.dropbox.com/s/bbh38zmt3edhx79/Pic%208.JPG?dl=0

Again apologies for the drop box links but I cant seem to work out how to upload pics directly...


So when I looked back at the pictures I noticed that there is a small spec of dust/dirt on the front side of the capsule. Not sure if this affects anything? Is this safe to remove or just leave it?

The main thing I noticed was the wire that looks to have been crimped/kinked in its box by the edge of the capsule... I decided to measure the DC Resistance of the two diagphram leads from the screw to FD and RD on the board. The (FD) with the kinked wire measured 5.8 Ohms resistance while the back diagphram (RD) connector measures 1.0 Ohm resistance. Not sure if that has anything to do with it?

If my wiring looks ok I will look to remove the capsule connections and do as Krumlee mentioned above!

Thanks for the help

Regards,

  Matt

 

[tskguy]

So the capsule looks to be wired correctly at the capsule... I don't see the wires at the board but I assume its correct there.  And I cant imagine the crimped wire would cause an issue.. You could trim the wire at the crimp and add a extension but that may be worse??  And just to be sure.. The red wire is going to the FD connection and the blue wire screwed in to the back plate of the same side is going to the FBK. Your older post confirms that as well.. So I would move forward removing the capsule and trying the other troubleshooting measures,

Eric

 

[Matt55]

Hi Eric,

Thanks for having a look!! I thought I understood your email about wiring it up and was pretty sure I had done it correctly.

The wire from the Front Diagphram goes to FD on the board. . (RED)
The wire from the backplate closest to the Front Diagphram goes to FBK on the board. . (BLUE)

The wire from the Rear Diagphram goes to RD on the board. (RED)
The wire from the backplate closest to the Front Diagphram goes to RBK on the board. . (BLUE)

I'll continue with the other tests Krumlee out-lined and report back.

I hope I can figure it out soon

Regards,

Matt

 

[Arkenberg]

Alright guys I might have a hard question to answer for you. I built my microphones and they work. The have good sound volume and good tone, now here is the kicker, there seems to be a lot of random static every once and awhile and popping  and cackling at about the same time. It is very random but it continual comes and goes. I figured it was the FET so I changed it and then I resoldiered everything. Also all voltage seems correct at diode and other places. But still the same thing is happening. So I am not sure what to do next besides starting over which would suck.
So if anyone has any idea what is happening please let me know.
Thanks guys.

 

[Arkenberg]

Oh also the mic pops loudly when switching patterns.

 

[fsalter]

"Oh also the mic pops loudly when switching patterns"...That is normal for the U87

 

[Arkenberg]

"Oh also the mic pops loudly when switching patterns"...That is normal for the U87

Thanks I did not know that, must have missed that in the read. But any idea on the random popping that i am having? It seems to cycle and I can't seem to pin point it.

 

[Matt55]

Hi Arkenberg,

Im not sure if you have read my posts above but maybe we are having the same problem. I just get like constant noise and crackling through the mic.

I tested every resistor and the FET and all my voltages appear fine, biased up fine also. The capsule is also wired correctly.

In my build its either a cold solder (which seems unlikely) or a busted component, most probably one of the capcitors but its hard to check because my DMM wont measure capacitance.

Just to ask, are you using the Styrenes from dany? Just wondering maybe they are bad? I cant test them currently as I have nothing to measure them.

Thanks,

  Matt

 

[Arkenberg]

Hi Arkenberg,

Im not sure if you have read my posts above but maybe we are having the same problem. I just get like constant noise and crackling through the mic.

I tested every resistor and the FET and all my voltages appear fine, biased up fine also. The capsule is also wired correctly.

In my build its either a cold solder (which seems unlikely) or a busted component, most probably one of the capcitors but its hard to check because my DMM wont measure capacitance.

Just to ask, are you using the Styrenes from dany? Just wondering maybe they are bad? I cant test them currently as I have nothing to measure them.

Thanks,

  Matt

Matt
I am using the styrenes from Dany.  I built two microphones and one worked great and the other one just was popping. Then I grabbed a bad cable and shorted the good mic. I fixed that by replacing the L1/L2 but now it pops as well.
It might be the caps but I also have no way to test them. I guess I can replace one by one. I guess I might also have to order more of dany's styrenes to troubleshoot.
Thanks for the Info
Jonathon

 

[Matt55]

Hey Guys,

So I haven't got any further with my D-U87 build.  Still producing only noise no signal. It seems everythings in the correct place and capsule wired properly and my voltages seem ok.

I thought the next step is to try and test some of the capacitors in the circuit as I tested the resistors before installing.

Now I have seen that masuring capacitance is one test but also measuring ESR is another. I have seen Electrolytics measured for ESR but no-where can I find information on measuring tantalums, polystyrenes and film capacitors.

So my question is can tantalums, polystyrenes and film capacitors be measure for ESR like Electrolititcs. If so I have a few DIY projects so it would be worth me getting an IN-Circuit ESR meter and a Capacitance meter for pre circuit installation.

If someone out there could advise me that would be awesome!!

Thanks for your time,

  Matt

 

[fazeka]

Hi,

Got my mic working a while ago but recently went to use it on a session.

Tried to kick in the pad and got no output... Tried it with different patterns, with the low-cut in and out. No dice: pad doesn't work.

I was going to dig into the schematic and check it out but wondering if anyone has any ideas or has encountered this before?

Thanks,
Chris

 

[fazeka]

Hi all,

Update: I fixed the problem with the pad, the wiring from the front backplate went to the wrong pin (note: this particular mic using the older DM-U87 v1.0 PCB). 

Now, I do have a problem with 2 out of 3 mics I have built where the fig 8 is not working right. Seems like this thread shows that the figure 8 issue is not totally uncommon. Typical problem where the fig 8 results in a muffled rear relative to the front and the fig 8 pattern about 10-12dB down relative to the known working mic's fig 8 output. I believe it is with the backplates not being isolated.

On the one mic I have where the fig 8 works great, there is no continuity between the backplates. I measured the resistance between this mic's backplates at 1.99M ohms.

On the one mic with fig 8 problems, my DMM measures continuity between backplates (Fluke 73III: single beep) and I measure 242 ohms between the backplates.

The other mic with fig 8 problems (note: my DMM does not beep), I measure 4.37k ohms between the backplates.

So I guess anything in the single digit kiloohm range and lower is still considered low resistance and thus continuity?!?

I am working with the capsule vendor to see what can be done about this.

Anyone else have this issue with the backplates and the above figure 8 problem with their capsules?

Thanks,
Chris

 

[Pip]

Hi Arkenberg,

Im not sure if you have read my posts above but maybe we are having the same problem. I just get like constant noise and crackling through the mic.

I tested every resistor and the FET and all my voltages appear fine, biased up fine also. The capsule is also wired correctly.

In my build its either a cold solder (which seems unlikely) or a busted component, most probably one of the capcitors but its hard to check because my DMM wont measure capacitance.

Just to ask, are you using the Styrenes from dany? Just wondering maybe they are bad? I cant test them currently as I have nothing to measure them.

Thanks,

  Matt

Matt
I am using the styrenes from Dany.  I built two microphones and one worked great and the other one just was popping. Then I grabbed a bad cable and shorted the good mic. I fixed that by replacing the L1/L2 but now it pops as well.
It might be the caps but I also have no way to test them. I guess I can replace one by one. I guess I might also have to order more of dany's styrenes to troubleshoot.
Thanks for the Info
Jonathon

Yes check all caps that is a likely source especially if you went with the Polystyrene caps as they hate heat and solvents so you have to be really careful when soldering and cleaning. I dont think an ESR meter is all that helpful with DIY but an LDC meter is invaluable. Lastly how closely matched are you R18 and R19 as these need to be really close, like 3 decimal places close. Read Chungers build thread again as it is really spot on.