u87 schematic weird components + zener diode voltage

Hey friends,

I've been looking at the u87 schematic and there's a few parts that I don't really understand what they are.

http://recordinghacks.com/images/mic_extras/neumann/U87-schematic-1972.png

Mostly:

1. what is S1 doing man?? Where is this mystical switch (I always thought the u87 only had 3 switches) and what does it do. I think it has something to do with phantom power though...

2. what is MS1?

3. u87 vs u87p

4. u87 vs u87i. Although this seems to be the difference between a 3 pin XLR and a 7 pin xlr...

5. What's the zener diode voltage?

Lemme know folks!

Dan

Look much more carefull to the schematic, where these parts are placed and look at the photo of u87i from recordinghacks - there you will find your answers

S1 = switching between powering via phantom power, or the (optional) 2x22.5V internal batteries; it's inside the mic body

MS1 = current meter (ammeter)

U87 vs. U87p = check the ***) annotation on the bottom left of the schematic; also http://www.neumann.com/forums/view.php?bn=neumann_archive&key=1000286117&v=f

U87 vs. U87i = indeed, a function of the output connector

aquitania said:

Hey friends,

I've been looking at the u87 schematic and there's a few parts that I don't really understand what they are.

http://recordinghacks.com/images/mic_extras/neumann/U87-schematic-1972.png

Mostly:

1. what is S1 doing man?? Where is this mystical switch (I always thought the u87 only had 3 switches) and what does it do. I think it has something to do with phantom power though...

2. what is MS1?

3. u87 vs u87p

4. u87 vs u87i. Although this seems to be the difference between a 3 pin XLR and a 7 pin xlr...

Lemme know folks!

Dan

Click to expand...

U87P = Phantom powered

U87i = XLR version

U87 = Tuchel connector

M1 is the battery meter for the original U87 that took 22.5V 505 batteries for power but had a switch to use Phantom power.

This mic is not to be confused with the present day U87Ai they are different animals. Do a search of my posts you will find some reading.

Thanks friends,

My questions have been answered!

Another one though:

What's the breakdown voltage of that zener diode? My guess would be 24V based on the name... but that's most likely incorrect.

Also, it's strange they put an ammeter in parallel with a resistor. It would make the 750ohm resistor redundant would it not? An ideal ammeter (and even not so ideal ones)  will act like a zero impedance.

Dan

Ideally yes, but that's one way to alter the measurement range of a meter - it's a current divider.

In a similar manner, a voltage divider would work for a voltmeter. In fact, the more expensive meters have a high-precision resistor divider (or several) inside.

https://www.youtube.com/watch?v=Rxy-VpSDPg4

Khron said:

Ideally yes, but that's one way to alter the measurement range of a meter - it's a current divider.

Click to expand...

Yes, altering measurement range makes sense. Good call.