If your Commodore C64 displays a black screen or strange characters then the problem could be the failure of the PLA U17 (MOS/CSG 906114-01)
But remember that most of the time the problem depends on the PLA but to be sure a test with the "DEAD TEST" cartridge should always be verified, because other components cause black screen / strange characters (RAM,SN74LS257,ecc)
I have made even this DEAD TEST CARD (check my Store)
TESTED and Guarantees 100% compatibility and operation with the following ASSY MOTHERBOARDS
- KU-14194