Neumann Vintage U87 Clone : Build Thread.

[kante1603]

@adeptusmajor:

Fet is biased,but the T13s didn't show up!  .... ???.... :.... ;D ;D ;D

Udo.

 

[geekmacdaddy]

Thought I would throw this out there...as I was perusing the Aurycle site, I looked at the A570T as possible donor instead of the A460 kit for one reason, the polar pattern selector. Same price as the kit. http://www.aurycle.com/aurycle-a570t-large-diaphragm-multi-pattern-condenser-microphone.html.

Geek

 

[berkleystudios]

no filter though. not a major issue but still doesnt have all three selectors on it

 

[xqtion]

Hmm... tried swapping XLR 1 and 2. No luck. I'm still getting 10.5mV instead of 10.5V.

By the way which pin is pin 1 on the potentiometer ? Is the pin closest to the screw pin 1 ?

Around what voltage should the drain measure without any resistor on R11 ?

 

[poctop]

Hmm... tried swapping XLR 1 and 2. No luck. I'm still getting 10.5mV instead of 10.5V.

By the way which pin is pin 1 on the potentiometer ? Is the pin closest to the screw pin 1 ?

Yes,

Around what voltage should the drain measure without any resistor on R11 ?

Yes The pin 1 is the closest to Screw, 
What do you measure in between the  2.2K  resistor, and on top oF Zener diode, this are the basic Supply Voltage to start with.
Hope this Helps, 
Dan,

 

[poctop]

2 More Little friend looking to mate transformer and capsule  ;D
Still Waiting to try T13 and BV11 

All Original : C7, C8, C10 Tantalum - C6, C1, C3, C15, C4, Polystyrene,  I have been able to get some 10pf polyS from a Radio Guy just in town  ;D,

Dan,

 

[xqtion]

Yes The pin 1 is the closest to Screw, 
What do you measure in between the  2.2K  resistor, and on top oF Zener diode, this are the basic Supply Voltage to start with.
Hope this Helps, 
Dan,
[/quote]

Between R18 and Zener, I get 40.6V.
And between R19 and Zener, I get 41.5V.

Any ideas what might be wrong ? Thanks!!

 

[kante1603]

no filter though. not a major issue but still doesnt have all three selectors on it

Exactly what I think,having all 3 is a must-have for me.

Udo("notoric experienced U87 user")

 

[kante1603]

2 More Little friend looking to mate transformer and capsule  ;D
Still Waiting to try T13 and BV11 

All Original : C7, C8, C10 Tantalum - C6, C1, C3, C15, C4, Polystyrene,  I have been able to get some 10pf polyS from a Radio Guy just in town  ;D,


Dan,

Cool Dan,

So you will be able to compare between the 10pf mica and styrene soundwise...

Have fun,

Udo.

 

[xqtion]

I've found something weird.

When I measure R18 and R19, I get 1.1k when it should be 2.2k.

Can this have something to do with my symptoms ?

 

[Hank Dussen]

Anyone knows where to buy these small toggle switches that they use for these mics?

 

[poctop]

I've found something weird.

When I measure R18 and R19, I get 1.1k when it should be 2.2k.

Can this have something to do with my symptoms ?

you are measuring the 2.2K in parralelle that is why you have 1.1K ,  you should get about 48V at pin 2 and pin 3 from the front end ,  and you should have around 24V or a bit less when you measure the Side of the Zener diode that is facing R16 150K, is your Zener diode oriented properly the black stripe must be facing R16 as well,  check you capacitor polarity. and double check for solder bridge or cold solder.
you really need to take the schematic for reference and go from there, most of the voltage are labeled on the originial schematic,

Hope this helps,

Dan, 

 

[xqtion]

I've found the problem.

The numbers on the PCB for XLR threw me off. I had literally connected 1 to 1, 2 to 2  and 3 to 3 of the XLR to the PCB.
But of course pin 1 of the XLR should of have connected to 3 ground and 2 to 1 hot and 3 to 2 cold. Duh...

Now I'm getting about 46.2V between zener and R18.

I'm running into one biasing problem though. The highest I can get the drain volt is 7.43V.
And potentiometer resistance is measuring about 26.5k.

Please help?

 

[poctop]

I've found the problem.

The numbers on the PCB for XLR threw me off. I had literally connected 1 to 1, 2 to 2  and 3 to 3 of the XLR to the PCB.
But of course pin 1 of the XLR should of have connected to 3 ground and 2 to 1 hot and 3 to 2 cold. Duh...

Now I'm getting about 46.2V between zener and R18.

I'm running into one biasing problem though. The highest I can get the drain volt is 7.43V.
And potentiometer resistance is measuring about 26.5k.

Please help?

Do you have your capsule disconnected ? did you use the middle pin of the pot and the one closest to the screw pin 1

 

[xqtion]

Yes pin 1 and the middle pin which is 2.

Also nothing connected to FC and RC.

 

[poctop]

Yes pin 1 and the middle pin which is 2.

Also nothing connected to FC and RC.

have you measured the top of Zener in regards to GND, to see if you have the 24V ish there ,
so red probe on black stripe and the other one on the other side,

 

[xqtion]

Yes I'm getting 23.22V on the zener.

Thanks for your help~ Any more ideas?

 

[poctop]

Yes I'm getting 23.22V on the zener.

Thanks for your help~ Any more ideas?

Note sure what happened with your connection as some point but if i remember well if R11 is out you shoulb be able to get the full load arround 20V on the right side of R11 , i would consider replacing the FET then try , it seems that your FET is loaded? ,
Hope this helps,

Dan,

 

[kante1603]

Anyone knows where to buy these small toggle switches that they use for these mics?

Hi Hank,

Looking at my B2 switches under a magnifying glas I can't see the brand,only that they are specified at 1,5A.
Doing a search for (sub-)miniature toggle switches it seems to be Salecom types.
Remember the pattern switch is a 3 position SPDT with center off,the others are normal SPDT.
Found this one here:

http://www.banzaimusic.com/Salecom-SKS08LP-Subminiature.html

There are some more to look at on their site.Since you are from belgium that could be a way to go,but I bet these are standard toggles.

Hope to have helped,

Udo.

Edit:They are exactly the ones!The specs ("20mA/20V") stated at the site are bu*****t,must be a typo.When zooming in there it looks identical to the B2 switches.Dimensions meet them precisely!Great,now I`ve even found spare parts!Please see attached pic:

 

[kante1603]

Here comes another one:

Height restriction problem for trim pot (R11) solved.Found this one here:

http://www.reichelt.de/Spindeltrimmer/962-20-20K/index.html?;ACTION=3;LA=444;GROUP=B23;GROUPID=3130;ARTICLE=3642;START=0;SORT=artnr;OFFSET=16;SID=13T1Hrb38AAAIAAA9EfA82e8ea4ec628ed638b45641452a29f413

Specs are 20KOhms,20 turns, just 6,4mm high.It´s longer than the one in the bom but does fit since there´s enough space to the front of pcb.
There´s a pdf on the site where more details can be found.

Please see attached file (sorry for the blurry pics,can´t do it better at the moment).

Cheers,

Udo.

Addenduman gave me a hint that reversing the pot makes it way easier to reach the screw-DO IT!Works perfect!