mc wrote:
I am installing a new low voltage outdoor lighting system. There are 5
x 20w spot fixtures and one Malibu Lighting 200W transformer.

After installing the 5 lights, I laid out the 12-2 supply. The
furthest lights (2 on one post = 40w) are about 70' from the
transformer, and I hooked them up first.

With only those 2 lights attached, the transformer is cycling on/off
every 20-30 seconds.

The transformer, fixtures, lamps, cable, and connections are all new.
I took pains with the connections.

What am I missing? Please help.

I don't know anything about transformers cycling on/off, but I did help
a friend (as ignorant of electricity as I am) shop for parts for her
Malibu lights. Seems like 50' was longest run that would work - can the
length of cable be the issue?