I have 2 time capsules in my network. I bought a new one because the old one's router died, but network and backups were ok. I started using new TM to backup data. I now need a file off old TM how do I access to old time machine to restore that f

Reset the old TC to factory.. no files are lost doing that.

Factory reset universal

Power off the TC.. ie pull the power cord or power off at the wall.. wait 10sec.. hold in the reset button.. be gentle.. power on again still holding in reset.. and keep holding it in for another 10sec. You may need some help as it is hard to both hold in reset and apply power. It will show success by rapidly blinking the front led. Release the reset.. and wait a couple of min for the TC to reset and come back with factory settings. If the front LED doesn’t blink rapidly you missed it and simply try again. The reset is fairly fragile in these.. press it so you feel it just click and no more.. I have seen people bend the lever or even break it. I use a toothpick as tool.

N.B. None of your files on the hard disk of the TC are deleted.. this simply clears out the router settings of the TC.

Then plug the old TC into the new TC by ethernet.

Go to the computer and use airport utility to setup the old TC..it should be set to bridge and you can turn off the wireless.

Then you can open the old TM backup. The method was to right click on the TM backup icon and select Browse other TM disk.

In Yosemite method is here.

OS X Yosemite: Use multiple backup disks