The base contains the electronics, azimuth motors and encoder, and the clutch.

Electronics

Not much to the electronics. The board design is by Tangent. Note
the version number of the main IC (V 15.13) - this is what the
hand controller reports when you select the version number.

The RJ12 jacks seen in the top photo are what all the motors/encoders plug-in to.
From left to right they are: azimuth slew motor and encoder, altitude slew motor
and encoder, azimuth tracking motor, altitude tracking motor.

Motors

The 2-speed DC slewing motor is on the left and drives a 288 tooth-48 pitch
gear. This is the gear used when the telescope speed is set to slew or finder.

The 3-speed DC-Servo tracking motor is on the right and drives a 266 tooth
48 pitch helical/worm gear. This is the gear used when the telescope speed
is set to center, 2x sidereal, or photo.

Encoder

The encoder operates at 8192 counts per 360°, providing a resoultion
of ~ 2.5 arcminutes. With Celestron's Enhanced Encoder Resolution
enabled, the encoder operates at 65536 counts per 360°, providing
a resolution of ~ 19 arcseconds.

Clutch

Getting to the base clutch isn't to difficult. To remove the encoder
you need to loosen a hex set screw (circled in red above).

Once the encoder is removed a large nut and washer needs to be removed.
This will allow the top portion of the base (with the forks and OTA)
to be removed from the lower portion by lifting straight up.

Also of note is the 899 written on the wall of the base. This is the
beginning of the serial number for my U2K. The serial number is also
stamped on top of that wall directly above the nut.

With the top portion of the base removed you will see the clutch with
its 62 oblong rollers. Also visible is the 266-tooth gear (gray disc
surrounding the clutch) with the 288-tooth gear below it. And visible along
the edge of the base are 3 roller bearings. Ever wonder what those 3 silver
circles are on the side of the base? Those are the axles for the roller bearings.