There were two different types of expansion units for the System 80. This is the early one with the S-100 bus.
The first card connects to the System 80 via a 50 pin interface. It also provides the floppy, parallel and RS232 ports. I particularly like the termination networks that have been added to several of the ICs.
The second card provides 32k of RAM. There was one faulty RAM chip.
The power supply unit is the same as the computer. I reformed the caps with a variac.
There is one spare slot for an additional card but the case is not great for adding additional I/O and there’s no obvious mechanism for adding more memory beyond the current RAM/ROM.