I determined that the Sharp Twin Famicom was working with regular cartridges. Great. I loaded a disk into the drive, however, and I can hear the Famicom disk go round and round, as if not busted.

Here is the first look:

Next, I systematically disassembled the internals of the Sharp Twin Famicom. Not surprisingly, I found dirt, cobwebs, insect larvae, dead insects, crumbs, and dust.

Here is the Sharp Twin Famicom in its primitive and dirty form:
 

So, I first concentrated on the Famicom disk. As I suspected, the disk belt snapped and turned into a sticky, rubbery paste, which is a pain to clean but must be done. This can be accomplished with a small slotted screw driver to scrap the belt off the wheel and motor. Next, use some alcohol to clean the remaining residue.

Here is the Famicom drive. Notice in the lower left-hand corner that the belt is snapped. The belt will need to be replaced:

Next, proceeded to identify the drive controller chip. If the drive contains the IC7201 drive controller, this drive can be used to read/write disks with Disk System copy programs; otherwise, it will contain the IC3206 which is an evil chip that prevents copying of Disk System disks.

Here are the results (sorry it is blurry):
 

In case you cannot see it, it's an IC3206. Bummer!

After some cleaning of the power board and the CPU, the Sharp Twin Famicom is starting to be restored to its former glory.

Here is the cleaned audio-video-power board. The solder connections look great:

Here is the the CPU. I got rid of the cobwebs and dead bugs:
 

After cleaning and even more cleaning, I reassembled the Sharp Twin Famicom minus the disk drive. Look how shiny and clean it is:
 

So what is next? I have to replace the drive belt. I have an extra one in my workbench shop. This will take a some time and effort to fix -- not difficult but tedious.