Scheops CMC3--U Problems

[Ritchie Paris]

Somebody have meet a very high drop P48 drop voltage with the CMC3 ? me yes, around 34VDC !

 

[Khron]

And how's that any different from what's specified on the schematic?

https://groupdiy.com/threads/schoeps-cmc5-inductor-values.73321/post-927845
Points 1 and 2, CMC3 should be seeing 8.4v.

 

[Ritchie Paris]

And how's that any different from what's specified on the schematic?

https://groupdiy.com/threads/schoeps-cmc5-inductor-values.73321/post-927845
Points 1 and 2, CMC3 should be seeing 8.4v.

?

 

[Khron]

Ok, where are you seeing / measuring that large voltage drop?

 

[Gus]

https://billthompson.us/bt/schoeps-mic-conversion/
One part you need to think about is the JFET to PNPs coupling cap values
abbey road d enfer had a good post about the coupling cap values if I find it i will link it if someone else does not find it before me.

 

[Ritchie Paris]

Hi Gus, many thanks to you, yes with pleasure, let me know...

The drop voltage I have is between HOT and COLD, but after many calculation it seems to be ok, but strange !!!!

 

[Khron]

The drop voltage I have is between HOT and COLD, but after many calculation it seems to be ok, but strange !!!!

"Hot" and "cold" being the XLR pins 2 and 3? Or... what are the points you're measuring between?

 

[Ritchie Paris]

???? Ground ! PIN 1 ! 1&2 and 1&2.

 

[Khron]

???? Ground ! PIN 1 ! 1&2 and 1&2.

And how's that any different from what's specified on the schematic?

https://groupdiy.com/threads/schoeps-cmc5-inductor-values.73321/post-927845
Points 1 and 2, CMC3 should be seeing 8.4v.

Have you even taken a look at the schematic in the forum post i linked there? If you did, you might have noticed what i was trying to point out there.

In XLR connectors, as per standard, pin 1 is ground (NOT "cold); pin 2 is "hot" / signal positive polarity; pin 3 is "cold" / negative polarity.

In the above-linked schematic, you'll note that in the case of CMC3, you should expect 8.4v between pin 2 (or 3) and 1, or 34v in the case of CMC5 (depending on whether R8 is bypassed with a jumper wire or not).