Does anyone know of an easy method to detect where the break might be
in the cable before I cut the other connector?

I have tried using a tone injector/tracer (for telecoms. cables)
however, as the signal is so strong, it couples onto the cable even if
is just placed nearby.

One method might be to use time-domain reflectometry. Transmit a
fast-rising pulse into one pin on the cable, while monitoring this pin
with a fast oscilloscope which can trigger on the rising edge. See
how long it takes before you see the effect of a reflection from an
open circuit (the voltage at the pin will jump) or a short (the
voltage will drop).

Figure an in-cable transmission rate of somewhere on the very rough
order of a nanosecond per foot. To work out the actual position of
the break, you'll need to know the end-to-end transmission-and-
reflection time (e.g. from one of the wires which still works) as well
as the end-to-break time. Divide the latter by the former, multiply
by the length of the cable, and that'll be where the break is.

P.S. Why are there so many unrelated advertising/religious propaganda
posts on this thread? It seems that it is not being moderated
regularly?

This isn't a moderated newsgroup, and it isn't specific to
radiobanter. It's an unmoderated USENET newsgroup, fed to radiobanter
by a gateway of some sort.

Some of the better USENET providers do filter out / drop the spam
postings, and quite a few individuals deliberately drop postings from
spam-origin sites (and/or from radiobanter itself).

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!