EA6700 in Bridge Mode, How to change password

Question

Evening all....another frustrating day trying to use my highly limited network skills.
Have an EA6700 in bridge mode to extend wireless signal to my gym (read garage with a rowing machine in it!) .... main router is an EA9600. Both units working fine but when I set up the EA6700 Bridge, I left the default password setup instead of making the password the same as the EA9600.
So if I understand right, EA9600 has dhcp on and is 192.168.1.1.....EA6700 Bridge has 192.168.1.138 (this is the IP I read from the device page of the EA9600. I switched dchp off and optioned bridge mode. 
I cannot get to the admin page of the EA6700 to change the password. If I put 192.168.1.138 in the google box it comes back with nothing. As I say, this IP comes from the device page of the EA6900.
Anyone point me in the right direction to get to the configuration page of the EA6700 Bridge to change the password to the same as the main EA9600 please? It sounds simple but many hours later :-( .... the perils of an amateur hour trying do tech things.
Just to note, devices in the garage (Sonos box, Panasonic TV, very old Sony laptop) are all hard wired to the EA6700 and work fine for music and video....the reason for the wireless is to connect to a Chromecast in the back of the TV. Also works great I just can't change anything.
Many thanks for any help you can give me .... think I'm close to answer but as normal missing key componets of knowledge

Answer 1

...ouch feared you might say that.
So essentially if you elect to go with bridge mode can you access the configuration pages ...if you have the IP number.
Now as it goes I also have an EA6500 which I'm trying to do the same thing on....e.g bridge mode access point for Chromecast and music bits. So I could try that without spoiling (in the first instance) what I already have working.
I have a proceedure for setting the unit into bridge mode (in fact I'm fairly sure one of you network hero's ...Furry Nutz / BigDave pointed me towards some time back) .... but everytime I do it......10 second reset / 30 second power off / re-power up.....it still refuses to find 192.168.1.1
If I swap out the main EA9600 router and put the EA6500 in place, I can get the dchp switched down, the IP address changed and bridge mode set. But If I just connect it to a laptop and reset/poweron/off, the laptop network dialog box just keeps going through a re-boot sequence. I tried a second laptop in case there was something odd on mine....same thing.
Any ideas why the EA6500 won't play well directly connected to the laptop RJ45?
Thanks for the support as always guys