Building mame box

Should be OK but would be advisable to use a in-line fuse say 1 Amp max.
the min. guess 500mA being better just for peace of mind should anything
go wrong.

There are a couple of ways to make the connection, using an adapter
lead or an adapter lead with one end chopped off to enable the
connection to your circuit and the other end plugging into a spare lead
from the power unit.

Another way is to use a 'terminal block' we call chocolate blocks these
looks like a nylon block that has two screws to hold each wire - you
simply cut the strip down to the number required.

Or you could use the good ol' crimp terminal to make connection....
whatever method ensure you decide insulate the connections with proper
insulation tape.

Although 20 Amps or so is available the current taken depends upon the
circuit that you are adding 130Ma in your case.

I've seen what 20 Amps can do....!
Busy repairing a TV set, the guy on the next bench just completed a
brand new computer with a Asus mobo, there was this almighty flash and
bang explosion I just avoided knocking the tube neck off, his Stanley
screwdriver was almost in two pieces!!!!!

He ended up a screwdriver less, a load of melted silicon as well as a
pile of soot! Gee, I thought the world was neigh... he was sick as a
parrot!

davy