Q: how do i manually set my ip4 address on my mac?,

Hi Miles, some device has a Static IP it seems.

Make a New Location, Using network locations in Mac OS X ...

http://support.apple.com/kb/HT2712

Is that Interface dragged to the top of Network>Show:>Network Port Configurations and checked ON?

The Interface that connects to the Internet, needs to be drug to the top of System Preferences>Network>Show:>Network Port Configurations and checked ON.

Then... Try putting these numbers in Network>TCP/IP>DNS Servers, for the Interface you connect with...

208.67.222.222

208.67.220.220

Then Apply.

If need be in Network>TCP/IP>, you can set IPv4 to Manually & enter IPs.

Click on Advanced, choose TCP/IP tab, by IPv4 choose Manually instead of Using DHCP.

Oh, OK, in that OS, click on advanced>TCP/IP>Manually.

But what did you enter for IP & Router IP?

Depends what your Router's IP is, can you check on another device that uses DHCP to find the Router's IP?

The IP & the Router need to have the same first 3 numbers, if the Router is 10.0.0. one then the above would work, but if 10.0.1.1, then you'd need an IP of 10.0.1.15

Well, a couple of thing...

Routers might have a Range of IPs to hand out set.

Routers may be setup to only allow certain MAC hardware addresses to connect, is either possible?

Anyway, 10.0.0.138 is what you want to enter manually for router IP.

I have 2 airport express base stations and a smart tv.

Try using just one and see if that works.

Good idea from Roam to try, but on IPv6, you'd normally turn it off, or possibly leave it on Automatic, except in Europe where it may be needed I hear.