Checking connections on desk

[Sookie]

Hi all,

An old desk that has been modified a lot has me puzzled about what is actually soldered internally on the connectors and how.
The schematic said some things which turned out to be different.
Since I don't know if I maybe overlook some of the amplifier design possiblities, I'd like to ask you.

I would like to know if there are ways to check for different types of connections on the inputs and outputs.
Balanced, unbalanced, electronically/transformer balanced, maybe Pin3 hot, what are the options?
Without opening it up, can I determine it somehow with a MM and testtone?
I know the TRS an XLR pinout rules, just have knowledge holes about amplifier design.

 

[pucho812]

should be easy to determine if the in's and outs are balanced with a DMM and test tones but as per design of transformer balanced and such either look at a channel or look at the schematic.  But then again the desk was modified so who knows. is it possible to find out the mods?

 

[Sookie]

It's not an easy task to get inside because stuff is in a wired studio unfortunately.
So please tell me how to test it.
Or give me an outcome of a certain possible setup.

eg. Hypothesis transformer balanced:
I should measure continuity between pin 2 and 3. And probably between all transformer in's a certain equal resistance, and between all tx balanced out's another equal resistance for all. (could have been wired with mixed tx's but maybe this helps determining).