Neumann Vintage U87 Clone : Build Thread.

[useme2305]

no i mean with a drop of isopropyl on a q-tip moving it along the gap between the backplates.

a tiny bit of dust or oil at that place can cause such problems and it can be easily fixed.

 

[Ricardus]

no i mean with a drop of isopropyl on a q-tip moving it along the gap between the backplates.

a tiny bit of dust or oil at that place can cause such problems and it can be easily fixed.

I don't really feel like this would have solved the problem. This was a direct short. No resistance at all between the backplates. I think I just got a bad capsule that somehow made it out of the factory.

 

[Icantthinkofaname]

Are there any recommended transistors to replace 2N3819 since it's only available in multiples of 2,500 with a 5,000 min order?

 

[Ricardus]

Are there any recommended transistors to replace 2N3819 since it's only available in multiples of 2,500 with a 5,000 min order?

I think the NTE312 is a direct replacement and 2N5457 is also good.

But if you are careful you can still find 3819's around. Most on ebay are fake though.

 

[Icantthinkofaname]

I think the NTE312 is a direct replacement and 2N5457 is also good.

But if you are careful you can still find 3819's around. Most on ebay are fake though.

That's why I was looking for an alternative option. Most of the ones on eBay are coming from China, so I'm avoiding them. There were a couple coming from France I was looking at though.

Also anybody know if the switch PCB will fit in the Behringer B2 Pro, or do I need to use the B2's stock switch PCB?

 

[fsalter]

‘There were a couple coming from France I was looking at though‘
Be careful. I bought some om eBay from France recently, and they were fakes.

 

[Ricardus]

A company called RSR Eletronics here in the US has some in stock. I ordered a few and the quality didn't look great, but I contacted them and they stand by them. They say they're testing in spec.

https://www.elexp.com/ProductDetails.aspx?item_no=112N3819&CatId=

Maybe someone here who can test them thoroughly would buy a few and let us know... They're 60 cents each.

 

[Ricardus]

Looks like NTE Parts Direct has some 3819's in stock, also.

https://www.ntepartsdirect.com/ENG/PRODUCT/2N3819

 

[Ricardus]

So I was watching a video on the tube of you last night, and saw this guy doing an Aston Spirit tear down, and I got a great idea. Look at the pic. They put a small piece of felt over the toggle of the switch to cover the larger holes in the mic body. Simple but effective. I went out and grabbed some felt and did this to my D87's. Looks great

 

[Ricardus]

OK, so here's the story with my figure-8 mode not working. I tested the backplates on my capsule and I had a dead short. I was like, "Well this is it!" I talked to John Peluso, and he asked me to send it back so he could have a look at it. So I unmounted it from the capsule mount (I tested it out of circuit but still in the mount because it was just easier) and sent it back. Two days later he gets it, and says there's no continuity between the backplates, and the capsule tests perfectly in spec. So I was thinking to myself I must be crazy. I literally tested the capsule a half a dozen different ways just to be sure, and there was continuity. So I went and tested the capsule in the working 87, and it tested fine. No continuity. Then I remembered something from when I took it out of the capsule mount. The center screw was sitting high, a little proud of the white plastic arc piece, and I just instinctively tightened it down without even thinking. Skip ahead two days later and it occurred to me that had to be the issue. I never tested the capsule AFTER I took it out of the mount. The thing is, the Peluso U87 capsules have a translucent piece of gold tape going all the way around the edge of the capsule. I'm talking about the screw that holds the plastic arc piece to the upright that mounts to the mic body. So at that point I was thinking maybe the top of the philips head screw had some burrs on it from a slipped screwdriver, and maybe they pushed through the tape causing the short.

So cut to today, I get the capsule back, and I mount it in the mount (mind you, I had already tightened the screw down and for extra safety I put a small piece of electrical tape over the screw), put it in the mic and solder the leads to the PCB, and it works fine.

So I called John on the phone to let him know, and he said it also could have been one side of the screw sticking up more, and tightening it into the mount might have caused one plate to shift a tiny bit, and caused an internal short in the capsule. He says the tolerances are that tight.

Well since I had already tightened the screw down, I couldn't test for which one it was, but the screw theory is the only one that seemed to logically satisfy both conditions (that I saw continuity and John didn't).

Anyway, the mic now works great. It's probably 2dB quieter than the other, but John says that's in spec for a U87, even from Neumann.

 

[Ricardus]

The post before wouldn't let me upload a pic. Said there was some sort of security risk. No idea. It was just a JPG. Anyway, this is the screw in the mount I'm talking about that either shorted the backplates, or caused one to shift enough to create an internal short.

Just because OCD I swapped out the FET In the quieter mic and got lucky. Now they sound the same to my ears.

 

[Ricardus]

Hi all

Anybody know where I can find the 3 switch for the U87 Kit ? may be with the PCB ?

Best and thanks

Anode

Right on Dany's order page:

http://www.vintagemicrophonepcbkit.com/orders.html

 

[roger.unc]

Hi - I am trying to perform a non-scope bias on the blue pcb version by getting the drain to 11.5v. With the red probe on the drain and black on common ground, it shows 22.9v and doesn't change regardless of where the trim pot is at. I have verified that the pot is varying between 25k ohms and on down when I adjust it. I have the third leg of the pot closest to the 2n3819 lifted from the pcb. Switches and capsule are not hooked up. Any ideas? Thanks!

 

[TillM]

check without phantom power the resistance from the trim pod.
Just put the black and red probe on the pins of the trimpod and check if you can measure the resistance.
Then turn the trimpod and look if the resistance change.
If not, then replace the trimpod.
Also double and triple check all components.

 

[roger.unc]

Hi TillM - thanks. I checked the trimpot. The resistance changes when turning the screw. Also, the drain on the second mic I built at the same time is also showing 22.8 volts despite the resistance changing on its trimpot when I turn its screw. So, if I have the same issue on both mics built at the same time with the same components, I probably have the same build error somewhere in both mics. 

 

[TillM]

Where did you buy the 2n3819?
Since the are obsolete there a lot of fakes ones especially on ebay.

 

[roger.unc]

Both 2n3819s are from small bear...

Edit: lifting the leg on the trim pot while it is installed on the pcb isn't necessary, despite all of the discussion about generally lifting one of the legs. I understand how these pots work. I just happened to lift the wrong leg - the one closest to the fet. After some rework, the fet drain voltage now responds to the trim pot with the leg soldered closest to the fet and the wiper soldered in the middle.

I originally lifted the leg because I mistakenly thought it was some custom requirement for the pcb - like some of the instructions to solder to pins instead of the pcb. Over and out...

 

[Ricardus]

Both 2n3819s are from small bear...

Do you have any idea what brand those 3819s are? (Or what brand they're supposed to be?)

 

[Ricardus]

I have the third leg of the pot closest to the 2n3819 lifted from the pcb. S Thanks!

Why? I remember soldering all three leads to the PCB.

 

[Ricardus]

I just graded all my FETs with that 9 volt battery method described here somewhere. The NOS Fairchilds had IDSS ranges from 2 to 6. The NTEs went from 5 to 8. So I bagged them all separately and labelled them.