Neumann Vintage U87 Clone : Build Thread.

[gary o]

http://microphonemod.wix.com/microphonemods#!capsules/c1z0e

Anyone using these guys capsules, I not seen them mentioned on here before but maybe I missed that sorry if I have

 

[kante1603]

Haven't seen them before either,thanks for sharing!

Udo.

 

[micaddict]

Yeah, thanks.

Italy based, it seems.

Relatively pricey, I'd say.

 

[Pip]

Stepped away from this thread for a while.  Just saw the posts about the AMI transformer wiring mis labeling.  AWESOME!!!!!  Mic level is SOOOO much better now, (dont have to crank the hell out of the pre to get a usable level)

I am noticing something new now though.  After being on for a while, the mic starts to get a crackle, almost like when a tube is going on a tube mic.  I cleaned the connections around the capsule wires, theres no residue or flux or anything there.  Any thoughts on what it could be (im guessing i could never hear it before i flipped the trafo). 
And could the fet bias have anything to do with it?

Check it out:

http://groupdiy.com/index.php?topic=48030.msg694109#msg694109

 

[gary o]

Yeah, thanks.

Italy based, it seems.

Relatively pricey, I'd say.

Yeah theGP K67 330 euros not far off the price of the real thing ....

I see lately venders selling capsules claiming to be like classic capsules  then they bring out a twice the price premium version.... its like saying the cheaper one we claimed to be like a classic totally wasnt like the classic we said it was....

Thats not to say that there are some good capsules out there for good prices & its great to have info here about the classic capsules about sizes materials diaphram thickness and so on

 

[micaddict]

Yup, the more info about what's available and where, the better. 

 

[OPR]

http://microphonemod.wix.com/microphonemods#!capsules/c1z0e

Anyone using these guys capsules, I not seen them mentioned on here before but maybe I missed that sorry if I have

Looks like the usual suspects at a higher price point!  ???

 

[Mickey Free]

Hello all, just finished my build and I'm really excited. The mic works, but there are some issues. My output is quite low, and there seems to be some noise in the signal, but that may just be the result of cranking my UA Apollo pre up to 50db to get enough gain, but my gut says it's not.

Also the pattern, pad and LC switches don't seem to really be working.

I read on here that low output is common, but i'm not sure if it has to do with the transformer wiring, as some have suggested, or the fet biasing, which seemed fine when I did it.

I also read that the trimmer screw touching the body sleeve may cause a hum issue.

Any thought? I'm a newbie and know very little still about trouble shooting. best place to start?

Thanks,
Mickey

 

[kante1603]

Hello Mickey,

first you should tell us what your configuration is,so which mic body,which transformer and which capsule.Also some clear inside pics from both sides might help.
Do you really have hum issues or does the mic pic up rf noise too?

Best regards,

Udo.

 

[Mickey Free]

Hi Udo, thanks for the reply.

My Mic Body is the more recent Behringer B2 Pro, My Capsule is the Peluso U87 Cap, and the Transformer is the Peluso T-87

The noise sounded like, well, noise...not quite like hum, more just like a noisy amp or something. It was subtle until you gained the pre up enough to use the mic. Not too familiar with the sound of RF. I will say this: when I had the mic in hand while powered on, there seemed to be less noise when I pushed the head basket down onto the body to have full contact (the head basket was somewhat lose from the body). Maybe it is hum, but just higher frequency than I am used to hearing? Thanks so much for your input.

I believe you helped me a month or two back with questions I had about the pattern switch pcb in the original mic, which I used but scraped all the traces (except ground traces) and then wired directly from switch contact points to the boards. I also of course wired the ground contact screw that attaches to that pcb directly to the ground pin on the xlr. If need be I can take pics of the switch pcb but that would be a bit of trouble and I'll wait till it's absolutely necessary. I'll admit the wiring got pretty tight in here. Anyways here are some pics of the inside of the mic:

 

[Mickey Free]

And the other side:

 

[kante1603]

Hello Mickey,

that looks like a bit of work now since there seem to be multiple issues you have.
From a first sight on your pics it seems like the fet is reversed or soldered in wrong.To confirm please send us a pic of it taken more from the side so we can see the fet´s leads.
The cap C5 on top looks burnt on one edge,you might have touched it with the solder tip.Swap it out.
I must say that your build is......ehhhheemmmmmmm.....not the cleanest I have seen,sorry.
Some solder joints don´t look too proper,wire isolations burnt etc.
For the noise issue,yes,sounds like a bad grounding amongst the metal parts (seems like it is rf noise btw.)
So if I were you I´d start to correct the cap and fet things first.
To get a working basic condition lift the wires from the switches (on pcb side) and isolate them with some tape for the moment.
With all these connections open the mic will now be in just cardioid mode meaning only the front capsule should work.
For testing you must assemble the mic body completely,it works as a Faraday cage,otherwise you´ll pick up lots of noise again.
And what is that black stuff at the transformer connections on the pcb?Not service-friendly at all.Try to get rid of it if possible,we might have to take a look at those connections too because I´m not familiar with this transformer wiring.
We can do dcr measurements on them later in case the mic level is still too low,maybe wires are swapped.

O.K.,that´s it for now,keep us posted and if possible send that before mentioned pic.

Good luck,

Udo.

Editic attached of what issues are visible atm.

 

[Mickey Free]

Thanks Udo!

Well, I never thought my soldering skills would be a source of embarrassment, but here we are  ;D!
Honestly it's good to here what's not up to standard so I can improve. I'm not on my computer right now so I'll have to wait to upload some more pics. But for now...

1. The black stuff is that liquid electrical tape stuff. Some of the shielding was melted away on the solder points to the transformer wiring do I thought that might help. Maybe not a great idea?

2. The Fet- I was worried about it being backwards as well, and originally I had it the other way, but I became confused when I looked at the diagram for this Fet, and then looked at the schematic Dany provided. It seemed to indicate that the drain and source were supposed to go to sources opposite of what was normal, where the flat side of the Fet faces toward the ground pin. I'm sure I must have been wrong, but I took it to an electronics repairman friend and after studying the schematic he said "hmmm, I think you're right." but we were both confused. When I get back to my computer I will send the part of the schematic I am referencing.

3. I will follow your steps to check the pattern set up, and when I do that I can take pics of the pattern pcb.

4. The extra ground wire you asked about is my ground wire FROM the capsule pattern pcb ground screw. I thought this would be an ok point to ground. Is that wrong? I was under the impression that all ground points in a circuit are shared or the same?

Ok I'll provide pics ASAP. Thanks again!!!

Best,
Mickey

 

[kante1603]

Thanks Udo!

Well, I never thought my soldering skills would be a source of embarrassment, but here we are  ;D!
Honestly it's good to here what's not up to standard so I can improve. I'm not on my computer right now so I'll have to wait to upload some more pics. But for now...

Don´t worry,we all were starters and did things wrong,no biggie.....

1. The black stuff is that liquid electrical tape stuff. Some of the shielding was melted away on the solder points to the transformer wiring do I thought that might help. Maybe not a great idea?

[/quote]
Not for service.
For preparing stranded wire just get some isolation off,twist the wires and give them some tinning.
Burnt isolations indicate a solder tip being too hot or-most of times-soldered way too long.

2. The Fet- I was worried about it being backwards as well, and originally I had it the other way, but I became confused when I looked at the diagram for this Fet, and then looked at the schematic Dany provided. It seemed to indicate that the drain and source were supposed to go to sources opposite of what was normal, where the flat side of the Fet faces toward the ground pin. I'm sure I must have been wrong, but I took it to an electronics repairman friend and after studying the schematic he said "hmmm, I think you're right." but we were both confused. When I get back to my computer I will send the part of the schematic I am referencing.

Best to check back the info on the fet,you can easily find it in the internet.Just type  in the name of the fet,it should be a 2N3819.You´ll get info and a drawing of the pins indicating which number is which function then.
If the correct fet is in then it looks like you and your friend are wrong,just follow the silk screen and where the flat side points to.It was never wrong in any of the revisions.
By soldering and desoldering you might have a faulty one now anyway,best to check this first,maybe your friend can do transistor testing?

3. I will follow your steps to check the pattern set up, and when I do that I can take pics of the pattern pcb.

As said we must bring the mic to a solid status first,so just lift the wires from the pcb for now to "force" it to cardioid mode.
This is the same condition as when the pattern switch is in middle position,so open(!) condition.

4. The extra ground wire you asked about is my ground wire FROM the capsule pattern pcb ground screw. I thought this would be an ok point to ground. Is that wrong? I was under the impression that all ground points in a circuit are shared or the same?

You´re right of course,I just asked what it is and what it´s for.When you said the mic is touch-sensitive by pressing the head basket down then it is definetely not grounded well,promised.

Ok I'll provide pics ASAP. Thanks again!!!

Best,
Mickey

You´re welcome Mickey.
Btw.,where are you located?If in the EU or close to germany I´d happily send you a fresh new fet(Fairchild 2N3819) if you want.In case you´re in the usa then maybe one of you other guys monitoring us  ;D could help Mickey (pretty close to christmas,isn´t it?).

Best,

Udo.

 

[gary o]

Not wanting to cause further confusion  re the FET but I came across different pin out versions of the 2N3819 other guys here were telling me they found some too .....so I guess check with the vendor where you get your FET for the correct pin out .... Udos kind xmas prezzy offer is good idea as he will know pin out for sure.

While I was making my homebrew U87s I used IC socket chopped into single sockets while I messed around with different FETs tho I soldered onto the gate... but reduces the risk of frying, crock clips worked good to heat sink the leads too, another chap here somewhere puts his components in the chiller of the fridge before soldereing ha I think thats great idea.

 

[kante1603]

Not wanting to cause further confusion  re the FET but I came across different pin out versions of the 2N3819 other guys here were telling me they found some too .....so I guess check with the vendor where you get your FET for the correct pin out .... Udos kind xmas prezzy offer is good idea as he will know pin out for sure.

While I was making my homebrew U87s I used IC socket chopped into single sockets while I messed around with different FETs tho I soldered onto the gate... but reduces the risk of frying, crock clips worked good to heat sink the leads too, another chap here somewhere puts his components in the chiller of the fridge before soldereing ha I think thats great idea.

@gary o

I did the same in one of my builds with chopped ic sockets,just soldered to the turret pin.Very useful for swapping them.Keeping soldering times short  and joints neat never damaged them.
If there are different pin versions existing we should point it out here somewhere,in my case I never came across any.I have more than a hundret,bought from different sources and manufacturers.
Best is to always check parts before soldering them,at least I do it this way.For transistors I have a small and cheap and simple checker,it shows what type is under test (so npn,pnp etc.),pin functions on several types (so pin number and corresponding gate,source,drain) and some more.
You can find them as kits everywhere.No precision stuff but cheap and functional.
"Cool" idea with the fridge,hahaha..... .

Hopefully Mickey's friend can test them.

Thanks for posting!

Best,

Udo.

 

[Mickey Free]

Not wanting to cause further confusion  re the FET but I came across different pin out versions of the 2N3819 other guys here were telling me they found some too .....so I guess check with the vendor where you get your FET for the correct pin out .... Udos kind xmas prezzy offer is good idea as he will know pin out for sure.

Thanks Gary, this is EXACTLY my confusion. I am using a Central Semiconductor 2N3819. Here is the pin layout:

https://drive.google.com/file/d/0B_VgtX4-ecrpaHIyZ1FSVV9zRDg/edit?usp=sharing

Now, according to the pin layout of this part, the drain pin is pin 1, meaning to it would face opposite Dany's instruction photo here:

https://drive.google.com/file/d/0B_VgtX4-ecrpbFphRHZndHI2R0E/edit?usp=sharing

And looking at the schematic, the source pin should lead to C8 and and R11:

https://drive.google.com/file/d/0B_VgtX4-ecrpb1BWQ2VXNGpHODA/edit?usp=sharing

so that is why I installed it "reversed" from the earlier pics. Maybe i'm just stupid, and this is all very new to me, but that seemed right.

Udo, I am in the US actually. I have a few extra fets I ordered just in case, so I may have to swap one of those if this one is fried. I will also follow your steps on the capsule test and report back. Let me know what you guys think about the fet. If the capsule works ok in cardioid, i will have to disassemble the headbasket and get pictures of the switch pcb. Not looking forward to that  ;D

Thanks SOOOO much guys!

 

[kante1603]

Hi Mickey,

can´t open the files in the links you posted,don´t want to sign up there.

Anyway,found this some minutes ago:

http://datasheet.octopart.com/2N3819-Central-Semiconductor-datasheet-88825.pdf

Bottom of page,but doesn´t say if this is top or bottom view.So it still could be reversed.Normally pins are shown in dotted circles or squares when seen from top,and then.........

As said best to test them prior to soldering.
Don´t forget to check the idss and the fet must be biased again if a new one goes in (you´ll have to disconnect the capsule for it!).

Keep us posted,that´s quite interesting now,

best,

Udo.

 

[Mickey Free]

Hi Mickey,

can´t open the files in the links you posted,don´t want to sign up there.

Sorry Udo, I fixed the links so all can view them now!

 

[kante1603]

Hi Mickey,

can´t open the files in the links you posted,don´t want to sign up there.

Sorry Udo, I fixed the links so all can view them now!

Thank you Mickey,

the second pic shows just how the fet is "normally" in,the third is the schemo we all know and have studied???
Link number one is from the same source as what I've found.
So still the question is top or bottom view.....

Best,

Udo.

Edit:If your friend is not having a transistor tester you can identify it yourself by trying a google search like this
http://www.zen22142.zen.co.uk/ronj/cpt.html
Sometimes it is even printed on the fet like "cbe".
Lots of ways leading to rome  ;D