Time Machine no longer working

Somehow this seems to have solved the issue.

The puzzle remains......we don't know whether it was the backup file that was corrupted, or the hard drive is starting to act up due to age.

I'm overly cautious, though, and won't trust it completely

Good strategy.

Unfortunately, all the normal steps to try to get backups going again have failed. Frankly, I doubt that erasing the Time Capsule disk will solve the issue, but there is really nothing else left to try at this point.

If you decide to erase the Time Capsule disk.......

Open AirPort Utility and click on the Time Capsule to select it

Click Edit in the smaller window that appears

Click the Disks tab at the top of the next window

Click Erase Disk

Select the Zero Out Data option on the next window

Click Erase

The process will take some time.....6-8 hours or so. The Time Capsule indicator light will blink amber during this process. You can watch the progress by opening AirPort Utility.

When the process is done, make sure that "Data" is selected as the backup destination and try to run a backup.

A 4th Generation Time Capsule is at least 9 years old and as much as 11+ depending on when the product was placed into service. The average useful life of this model was about 5-6 years, so you have had remarkably good luck with the product.

But, even if it were operating "normally", both the power supply and hard drive are overdue to fail, so you would not want to keep any data on the Time Capsule hard drive that you cannot afford to lose......unless.....you are also backing up to another hard drive.

"Preparing" is a tough one. If you stop the process, it has to start all over again from the beginning, so you wind up i n what might be an endless loop. Our normal advice is to let "Preparing" run until the backup completes.....or.....until you see an error message appear on the screen.

The other option would be to erase the Time Capsule hard drive and try to start over again with a new backup. Unfortunately, there are no guarantees that this will solve or help the issue at hand due to the age of the Time Capsule.

Let us know what you decide.

I would let "Preparing" run until a backup completes......or.....until you see an error message. If an error message appears, post back with the exact text of the message please.

If you decide to erase the Time Capsule disk, you would not use Disk Utility for this. Post back for more instructions if you want to erase the Time Capsule disk, since Disk Utility would only be used for a drive that is connected directly to your Mac via USB or Thunderbolt connection. The Time Capsule is a "network drive", so it requires a different approach for erasure and reformatting.

Can I just connect another external hard drive to my router and set it up in Time Machine for automatic backups?

Yes, if your hard drive is a NAS (Network Attached Storage) device that connects to your router using an Ethernet cable connection.

Possibly, if your external drive is a USB drive and your router has a USB port that will support Time Machine backups. Unfortunately, there are very few routers will do this. Synology is one, and some of the upper end Asus routers will as well.

I receive an error message that says it can't find the backup disk

Unfortunately, erasing the disk is probably not going to help your Mac find the disk on the Time Capsule, so the first task is to get your Mac connecting to the Time Capsule disk.

The disk on the Time Capsule is named "Data" by default.....unless you have manually changed the name of the device.

Click on the Time Machine "clock" icon at the top of the Mac's screen

Click on Open Time Machine Preferences

Click on Select Disk

Look to see if Data appears as disk

If yes, click it to select it, then click Use Disk

Power off the Time Capsule

Restart your Mac

Power the Time Capsule back up again

Time Machine can now find the Data backup disk and run a backup

I only use the Airport Extreme Time Capsule for storage (these backups) and as a hub to connect a couple of things

Time Machine cannot run unless it can find the backup disk on the Time Capsule, no matter whether the Time Capsule is used as a router or a simple storage device.