DK and DKjr are similar designs, and as such, the failures and symptoms of these failures are very similar. The main differences between DK and DKjr are in the sound generation hardware for music as well as few differences in the amount of program store and size of the video sprites.

There is much more technical information on my DKJr Tech page, much of which is applicable (or identical to DK).

When the game first powers up, it performs a series of selftest diagnostics to insure the game is operating properly. This kit can also be a useful tool for debugging broken boardsets.