Check the two large connectors are not reversed.

Check the 2 remote logic fuses are good game will not boot if one is blown

Rebuild power supply

Check for a shorted diode on locked coil

Pinside_forum_7524885_3341210 (1) (resized).jpg

Voltages for Logic must be clean the capacitors are 40+ years old time to rebuild the power supply.
The caps need replacing on the sound board also.

In the beginning of Black Knight production run, the transformer was located in the backbox, and the game used power supply board part# D-7999, with a stand-alone General Illumination Relay mounted to the backbox floor. During production, the transformer was moved to the lower cabinet and the G.I. Relay was then mounted on a new power supply board, part# D-8345.

With the driverboard un attached:

The cpu will show a Zero then flash off then back to 0 with Black Knight software pressing the diagnostic button will flash zeroff and back on if the Ram 5101 is faulty it will show a 9

Bench test cpu with driver board removed diagnostic using Black Knight Software:

Cpu boots to Diagnostic flashing zero -off then back on either an 8 or a 0 depending on software revision = game software and 5101 and Mempory protect circuitry ok pressing the diagnostic again will repeat the test: zero off then on.

Pressing the diagnostic button with IC 26 removed = 7
Pressing diagnostic with ic 20 removed = 5
Pressing diagnostic with ic 14 removed = 6

Cmos RAM Memory test:

Pressing diagnostic with 19 removed = 9
Note: a faulty 5101 or memory protect fault 9 will not be seen unless game software is ok

With Roms 26,20,14, removed =5
Diagnostic 5 when IC 20 is removed-faulty (resized).jpgDiagnostic 6 when IC 14 is removed-faulty (resized).jpgDiagnostic 7 when IC26 removed-faulty (resized).jpgDiagnostic 9 when ic19 removed-faulty or mem protect circuit (resized).jpgDiagnostic Pass BK ROMS flashing off to zero zero or 8 (resized).jpgIMG_20230422_132904214 (resized).jpg