I am trying to rescue old (but important) files from a Power Mac 7600 and an accompanying ZIP drive, neither of which have USB ports, so I only have serial and SCSI ports to work with. The Power Mac has a faulty power button and a very old OS that does not seem to support connecting to the internet. Is there a SCSI to USB adapter that will work for this application, or a way to tap into the hard drive and retrieve the files? Or is there some way to use the Ethernet port to get onto the web or Cloud?
I have not done this myself, but quick googling shows AppleTalk is available on System 7, so find some USB-to-serial adapter and another computer where you can run something that's AppleTalk compatible.– dirktJul 2, 2022 at 19:38
USB-SCSI adapters were made, but they weren't manufactured in great numbers, the controller ICs are now out of production, and, at least for the one featured on Adrian's Digital Basement, didn't support running off standard USB Mass Storage device drivers when connected to hard drives.
I can suggest four options, based on what you've described:
If you have a way to get new software onto the old mac: searching for something like "Classic MacOS TCP/IP" will pull up various articles on getting vintage macs and modern machines to talk to each other over Ethernet.
If you don't have a way to get new software onto the old mac, but your new computer runs a POSIX OS like modern macOS or Linux: Plug the Ethernet port on the old mac into your regular network or, using a crossover cable, into a USB-Ethernet adapter plugged into a modern PC running Linux or MacOS. (If your USB Ethernet adapter is a gigabit device, Auto-MDIX is mandatory in the spec, so any kind of cable should do.)
Then Install netatalk and configure it to present your new machine as a legacy AppleTalk-over-Ethernet file server you can interact with using the support built into MacOS by the time macs came with Ethernet ports.
If you can justify the cost of a hard drive replacement device meant for keeping retro hardware alive: Buy something like a SCSI2SD which allows you to install an SD card into an old machine as a hard drive, install it in the old mac alongside the existing drive, then do one of the following:
Boot off the original drive and copy your files onto the SD card... essentially retrofitting an SD card reader onto your vintage machine, similar to how I use passive CompactFlash-to-PCMCIA adapters as removable storage in my pre-USB vintage laptops.
Boot off the SCSI2SD, which has been loaded with a newer version of MacOS with updated network support.
If you really want something that plugs into USB or SATA: Buy an IDE/PATA Zip drive on eBay that doesn't have The Click of Death. Install it in your modern PC using either a PATA-to-USB adapter that supports ATAPI or a PATA-to-SATA adapter.
Copy the existing files off the Zip disks, then put them back into the old mac and copy the files from the hard drive onto them for transfer.
(I'm reluctant to recommend this one since I lost some of my childhood files to a Zip drive going bad and I've since learned that Iomega hardware was cheaply made in general.)
For any of the non-network solutions, you may need software on your other machine to read HFS+ partitions if the old mac doesn't have DOS file exchange support installed and your new machine isn't a mac, but that's easier. (Linux comes with HFS+ support and Apple released HFS+ drivers for use with Boot Camp, not to mention multiple standalone tools for both Windows and Linux.)