What's Wrong With My Tascam Portastudio 488 Mkii

This time, we're taking a look at a classic (yet faulty) recording console from the late 90s. This is, of course, the Tascam Portastudio 488 MKII. This is an 8-channel recorder with built in preamp, that records your audio to high performance cassette tape.
This particular unit powers on....sometimes. Its not consistent, nor is it predictable, but it will turn on sometimes, and I need your help to isolate what's going on here. Let me know if you have any troubleshooting steps I should try!