On Dec 19, 3:58*pm, Sjouke Burry s@b wrote:
klem kedidelhopper wrote in news:5637a840-
:









I have a job to run about 35 speakers including cameras and security
through *a building. The building is a sprawling 200 year old Behemoth
of a place that I don't want to try to fish wire through. The building
was part of a now defunct college and as luck would have it almost
every room is home run wired back to a closet with at least 4 CAT5
wires. This closet seems like a good place to install our equipment
and so we plan to run the alarm system as well as the cameras off
these CAT 5's. In addition there will be a background music system.
The music will be very soft and so I would like to go with 70V lines
with speakers tapped at .25 to .50 W each. The runs would be no more
than say 100 to 125 feet and so I don't think that the 24 gauge wire
should be a problem with each CAT5 cable handling one or even two
speakers apiece. So anyhow that's the job and I'd appreciate any
comments on that but my other question is this: I have boxes of
unidentified line to voice transformers. I don't know if they're 70 or
25 volt units. Is there an easy way to determine this? I don't have an
impedance bridge. Thanks, Lenny

Try to find the saturation voltage of the trannies.
Put a variable 50(or 60) hz voltage on one, measuring the
current.
When that current suddenly starts to increase, you are over
the saturation voltage.
Subtract about 30 % to grade the trannie.

So then assuming the UUT is in fact an unknown 70V transformer, I
might have the supply cranked up to almost 100V before I see this
increase in current? Can I feed this transformer off my bench variac?
Will this current increase be a sudden or very gradual increase? Lenny