I've had some experience doing light restoration to 3 of them. The auto-reverse deck is quite rugged overall actually but the motor has no speed adjustment at all & the head is prone to electromagnetic interference without a ferrous collar around the deck motor if you replace the motor with a mabuchi or whatever. The bottom deck will sometimes fail in the play position with transport in the up or Play position which in turn leaves the rubber of the pinch roller resting against the capstan pin. This leaves a dent in the roller which will need replacing if that happens. The silver face sometimes comes unglued from the cabinet & the bottom right knob for the mic mixing is different from the rest in its position so you cannot substitute any other knob. Weird but true.
There are I believe 13 0r 14 different connections that have to be unplugged before you can remove the guts from the cabinet & no way of servicing either deck without removal of the chassis/guts. just a heads up before you dive in. You must be organized & able to effectively mark connections accurately as many connectors can fit more than one location. I number them with a marker & painters tape during disassembly to keep everything straight.
Finally, when adjusting azimuth(head alignment) on deck 2(top auto-reverse), it will quickly come out of alignment after a few cycles back & forth in play direction unless you use some loc-tite or mild glue to secure the adjuster screw of the playback head.
Good luck. I love mine & really fell in love with this beast. It really is pretty much everything a great boom-box needs to have, including the VUs, Big bright power LEDs & giant shiny bumper bars...
Oh, & the power output is unreal!! I put my volume on 2 & my ears bleed, lol!