Wow, lots of answers and help - thanks guys!
To answer the questions:
Yes I did try all the channels in the mixer
to check they work. They all had a mic directly plugged in and worked perfectly.
I was using a dynamic mic and also an iPod going through a DI box to create 1 channel of
XLR. Both methods of testing the line had the same results.
signal in the cable as each test was replicated directly into the mixer (bypassing the
patch bay) with satisfactory results.
I don't know if the patch bay was
working previously. The equipment is 4 years old and I've only recently started the job.
The equipment has been rarely used and poorly maintained.
Today I have got
some signal from the iPod/DI box method but need to crank it up too high in order to get
enough volume. This distorts the signal and causes either a hissing sound or a noise
similar to that of an idling jet engine. Even at full volume on the iPod, gain, fader and
padding the level of audio is really too low.
Now, there are 2 patch bays in
the room (both XLR to XLR), the one further away from the mixer has less signal/more
hissing than the one closer. There is consistent behavior within all the lines in the two
different patch bays.
( "patch bay" / "patch panel". Which is correct? I wasn't
sure which to use. )
I do have a signal tester. How would I use it here? Which
points should I test across?
Thanks everyone for your time and assistance.