Here are the schematics for the Atari 2600 Jr. They were used when I designed and built Bankzilla, so I'm fairly certain
they are good. Note that the RF modulator is not shown (I doubt it would ever be needed anyways). "IF out" on the last
image is the signal that runs to the modulator. It is baseband video with the sound carrier riding on top. Also, note that the
cart connector is not shown. It simply sits on the data bus (D0-D7), the address bus (A0-A12) and power (+5V/GND).
This is the power supply. Nothing special here.
Pretty standard crystal oscillator.
The controllers and console switches. Note: only one controller channel is shown.
The 6532 RIOT.
Composite video generator circuitry.
Oscillator for the sound carrier.