Adding my old Asus RT-68U as a repeater problem

[Webfanatic]

Hi

I just got a new RT-87U to replace my RT-68U as my main router. So, i disconnected the RT-68U and set the RT-87U and set everything up and it went fine.

However, now i want to use the RT-AC68U as a repeater but everytime i connect it to the network to try to set it up, the network sees it suddenly as my "main" router and then the 87U becomes disabled. The 192.168.1.1 IP address is then put on the old 68U.

How do i set this up properly? Ive tried to reset the 68U router but this doesnt help.

I just want the 87U to have the 192.168.1.1 IP address and acting as my main router....and the 68U as a repeater with a different IP address (doesnt matter what it is)

Thanks in advance.