PCB Repair: Killer Instinct 2
Problem
Bad sound.
Diagnosis
The game would occasionally sound two ‘bongs’ on boot, which would normally indicate a U10 sound ROM error. However, these bongs were played at a lower pitch than usual and sometimes the game would emit an ear-piercing screech instead.
I verified ROM U10 out of circuit against the known-good checksum. It looked like somebody had tried to ‘reflow’ the socket pins, scarring the PCB in the process:
As of this time, schematics for Killer Instinct 1/2 are still being hoarded so I traced a out a mini-schematic of the connections between the sound ROMs and the ADSP-2105. A set of three HC541s buffer the data and address signals:
U14 buffers the lower 7 address bits. Examining with the logic analyzer, I found a mismatch between the two sides:
Bit 1 was occasionally low when it should be high. Replacing the chip restored full sound.
Fix
Replace 74HC541 at U14.
