Neumann Vintage U87 Clone : Build Thread.

[kante1603]

Now i found out that i have some continuity between the primary and secondary winding. Is this normal? my other t13 doesn't have that. Is my transformer bad?

-Leifur

Hi,

is it when trafo is out of circuit?
If so then yes,there should be absolutely no continuity between primary and secondary.
Looks like a bad trafo,sorry.
This explains why you loose the drain voltage because it loads down the circuit.

Heads up,

Udo.

 

[LG]

Thanks Udo for quick replies,

I guess the only thing to do is to contact Michael at Digital Audio Service Hamburg and see if he/they are willing to take it back. Crap.... But still I'm glad i could trace this my self

Is it possible I could have harmed the trafo my self by only shortening the hookup wire and soldering it to the pcb?

-Leifur

 

[kante1603]

Thanks Udo for quick replies,

I guess the only thing to do is to contact Michael at Digital Audio Service Hamburg and see if he/they are willing to take it back. Crap.... But still I'm glad i could trace this my self

Is it possible I could have harmed the trafo my self by only shortening the hookup wire and soldering it to the pcb?

-Leifur

No,that's unlikely.Most of times it is caused by mechanical stress,not by reversing wires.
Michael seems to be nice,he helped me getting mine.Have bought another pair from last week,he told me he has only two left but has more on order.Shipping from TAB Funkenwerk to him doesn't seem to work too good,last time it took ages to get mine.I always do a dcr test when I receive them and report back to Michael.

So hurry up,

best,

Udo.

 

[LG]

The email has left my headquarters.... we'll in a way it's good the i get some troubles, with no flaws you don't get to troubleshooting, and troubleshooting means learning something new for a newbie like me

-L

 

[djvibe]

Would you please post some photos on how you wired the switches on the B2 body with the black plastic. I see a lot of mentions of pictures but I cannot find them. Thanks again!

 

[LG]

Hi djvibe,

On the first page in this thread there is a link to a document made by Udo. It's for the none plastic version but they'r the same. You have to cut the same trace (or just make sure no connection goes to ground). The only way for me to make good connection was to solder the wires directly to the lugs (se photo). I cut some of the plastic away for making some space for the wires, one could as well drill big holes for the wires to go trough.

-Leifur

 

[kante1603]

Nice info Leifur,this B2Pro version was indeed not covered yet I think.
Thanks for sharing!

Udo.

 

[Deepdark]

Concerning the b2 pad and low cut switches, do I have to cut the traces that go to the ground or it must be grounded?

 

[LG]

I guess the switch is supposed to be grounded, just be sure the solder points aren't (where you make contact to the wire). There is only one trace to cut on both types of the pcb. So after you're done check if you have continuity between the solder points and ground, if there's none you've done a good job

-L

 

[djvibe]

Hi djvibe,

On the first page in this thread there is a link to a document made by Udo. It's for the none plastic version but they'r the same. You have to cut the same trace (or just make sure no connection goes to ground). The only way for me to make good connection was to solder the wires directly to the lugs (se photo). I cut some of the plastic away for making some space for the wires, one could as well drill big holes for the wires to go trough.

-Leifur

Thanks for the photos Leifur. The capsule is then still soldered to the pins in the black plastic, correct? And I remove the existing wires from the switch board to the pins, correct? Thanks again for you help on this!

-Vibe

 

[LG]

Thanks for the photos Leifur. The capsule is then still soldered to the pins in the black plastic, correct? And I remove the existing wires from the switch board to the pins, correct? Thanks again for you help on this!

It's actually up to you. I decided to remove it an to use wires in stead. If you go on and remove the bottom plastic thing you could as well cut it up in to thin stripe an use it as a spacer for holding the rail in place (se photo).

-L

 

[phonofranz]

Hello everybody,

first of all: thanks a ton to everyone involved. I'm learning a LOT from this thread.
I took the time to read almost every page and I'm now building my clone in a B2 (non-pro) body. Cinemag 2480/Rk87/original parts, except 10pf cap.

Testing the PCB I had the same impedance-related issues as Deepdark regarding the backplates' pad voltages: cheap DMM reads about 17v instead of 40v. Doubled check. Everything else seems right-ish.
IDSS=7,6. Bias set for symmetrical clip with a JS-plugin scope included in Reaper.

I'm still waiting for the capsule to show at my door (probably stuck in Italian customs atm) to check if the mic is working.

Any pointer/link to the high-impedance measuring buffer Matador cited?
Is it something we could build and use for this kind of projects?

Again: thanks for all the knowledge you're sharing!!!

Franz

 

[Deepdark]

Haha phonofranz, same donor, same capsule, same tranny, same backplate voltage Let me know when you'll try it with the capsule. I think a true RMS DMM could pick up better reading. Question, how do you mount the trany? 

 

[kante1603]

I think a true RMS DMM could pick up better reading.

No,this is about measuring dc in a very high imp. area,not rms for ac or pulsed/modulated dc etc. at a given frequency.

Udo.

 

[Deepdark]

Thanks Udo for the clarification so I guess a scope with high z probe should do the tricks?

 

[kante1603]

Thanks Udo for the clarification so I guess a scope with high z probe should do the tricks?

I'm not sure if the input impedance of a scope-even with a 1:10 or 1:100-probe is high enough.
I guess we must look more to the giga-ohms side to get serious results.
E.g. my scope has just 1M-Ohm on the inputs,that is way too low.

Best,

Udo.

 

[phonofranz]

Haha phonofranz, same donor, same capsule, same tranny, same backplate voltage Let me know when you'll try it with the capsule. I think a true RMS DMM could pick up better reading. Question, how do you mount the trany? 

I drilled a couple holes in pcbs to place them higher and make room for the transformer.
Then I've shaped a metal strip with pliers to hold the transformer in place with zip ties.
Very similar to Chunger's way: http://studio939.blogspot.ca/2012/12/vintage-u87-circuit-clone-microphone.html
except I use some heatshrink to "rubberize" the whole metal strip

 

[LG]

Hi everyone,

Just wanted to share some pictures from my painting session.

all the best, Leifur

 

[kante1603]

Nice copy (the blue one) ;D

Best,

Udo.

 

[LG]

Thanks for the likes guys!

Udo what did you do about the markings? (LC, Pad, pattern) Is there someone who has some nice suggestions other than permanent marker?

-Leifur