Default IP-Addr: 192.168.0.1
Beware: The access point mode does not exaxtly what you might think it does!
It removes the static ip and switches to DHCP-aquired. However, it does NOT turn off the internal DHCP server! So you cannot have it inside your network for now. You either have to enable DHCP for client and so you can use http://tplinkwifi.net which resolves to its IP-address. (This works because the DHCP server sets the DNS resolver to itself.)
OR you can try guess its IP-address. Leases are in the range from 192.168.0.100 to 192.168.0.254. My client was .100 the first time I connected. I think the router assigned 192.168.0.254 to itself after the settings change.
Oh and the LAN and DHCP settings are unter "Internet" because... ???