Flying Shark Repair Logs
Source: Flying Shark (Sky Shark) - Taito 1987 (repair log)
The part of the board handling sprites is in a corner with 2148 type RAMs (55ns!). 3 of them have been "beheaded", probably due to poor storage. I installed brand new ones @ A27, A28 and B27. This fixed the sprites issue:
Concerning sound, I replaced all electrochemical type capacitors but that didn't changed anything (but it can't harm, original ones were 29 years old!). Then I "listened" to the signal at the output of the pre-amp: it was clear. So I simply replaced the audio amp (MB3770) and sound was restored.