One of the most common reasons technicians look for the datasheet is to identify the pinout. Hybrid ICs like the STK412530 usually come in a Single In-line Package (SIP) with staggered leads.
Measure the voltage at the output pins (before the relay). If you see high DC voltage (close to the rail voltage), the IC is blown. stk412530 datasheet
The STK412-530 has several protection features, including: One of the most common reasons technicians look
Power amplifier IC (audio power amplifier, hybrid SIP). stk412530 datasheet