Polarity of RFZ console inputs/outputs

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dukeofearl

Well-known member
Joined
Jan 7, 2016
Messages
77
I have a 1980s RFZ MP-4084 console from the DDR. I'm in the process of replacing some of the din, trennklinke and tuchel connectors, and I'm having a difficult time determining the correct polarity. Someone already installed XLRs for the mic inputs, but I'm not sure they did it correctly, because it was done differently in different sections.

The console is in three sections, the main unit (8 channels plus master etc) and two additional 8-channel units. Pin 2 from the mic input xlr goes to different pins on the mic preamp modules (KV80) in the different sections. The line outputs are mixed up as well.

Perhaps someone here could help determine the answer to the input polarity by looking at this part of the schematic? If you look on the left, AB5 and AB3 are the two input pins on the preamp module. Currently, some of the mic inputs are wired pin2 to AB5, and some are pin2 to AB3. Or maybe it doesn't matter as long as the input and output on each channel are matching?
 

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Here's the full schematic for the KV80 preamp module.
 

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Checking polarity is pretty straightforward. Use a two channel scope. Put channel one on your input signal. Put channel two on your output signal. Send 1K to the desk. First check your test setup, you should have two sine waves with matching polarity. Then the same when you test a path. Reverse wiring as appropriate.
Dont have a two channel scope? Then maybe you are not equipped for the task.
 
Hello,

AB5 -> a -> + of signal or in phase
AB3 -> b -> -  of signal or out of phase.

Best regards!

jokeramik
 
That´s not OK.
Why?
In this multi-pin connector, only every 2nd pin was occupied to achieve a better SNR.
It is important to count all.
It is important to also count the unoccupied positions.

Best regards!

IMG_5527.jpg
 
Last edited:
That´s not OK.
Why?
In this multi-pin connector, only every 2nd pin was occupied to achieve a better SNR.
It is important to count all.
It is important to also count the unoccupied positions.

Best regards!

View attachment 125439
Yesterday I was spent an hour to figure this out, look how pins AB2 and AB3 goes to the gain switch and also connected to pins 1 and 5 at the mini Tuchel connector (mic input).
None of the Tuchel pins are not connected to AB5 on the card.
AB5 on the card connected via a wire to points 8 and 9 on the schematic.
Untitled-2.jpg
 
You don´t understand what I mean. Look at the schematic. 0 Volts at Pin AB 13 and Pin AB 29. Pin 29 is the last pin of this multiconector. So it is important that you count the used and unused places of the multiconnector.
The way you count it now, the phase changes and the amplifier works out of phase.
HOT is AB 5. It goes via some Resistors and switch S1 to soldering point 10. This is the beginning of primary winding of the transformer. This the yellow wire of the transformer.
COLD is AB 3. This is the red wire of the transformer.


Best regards!
 
Last edited:
You don´t understand what I mean. Look at the schematic. 0 Volts at Pin 13 and Pin 29. Pin 29 is the last pin of this multiconector. So it is important that you count the used and unused places of the multiconnector.
The way you count it now, the phase changes and the amplifier works out of phase.
HOT is AB 5. It goes via some Resistors and switch S1 to soldering point 10. This is the beginning of primary winding of the transformer. This the yellow wire of the transformer.
COLD is AB 3. This is the red wire of the transformer.


Best regards!
It still doesn't make sense to me.
I took another look at the schematic.
Point 8 on the PCB connected to pins AB5 of the connector and it's also marked on the schematic as input 2, unbalanced, while AB2 is connected to S1 the same way as AB3.
So if you trace the PCB leads you'll see that AB2 is connected to S1 and sending the HOT signal to point 10 (primary of the input transformer) and AB3 taking the COLD signal to S1 and to point 13 (the other end of the primary winding).
Also the mini Tuchel connector of the mic input 1 (on the back side of the console at the bottom row) is connected to pins AB2 and AB3 and not to pin AB5.
And when you look at the connector wiring diagram on the schematic you can see that AB2 and AB3 are connected with the same balanced cable with hot, cold and 0V while AB5 is an unbalanced connection AB4 0V and signal at AB5.
 
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