Soldering and assembling

The 6-channel speaker selector board uses both surface-mounted and through-hole-type components. To minimize soldering difficulties, we recommended soldering all the SMD components initially.

The most recommended soldering orders are listed below:

1. STC15W201S MCU (U2)
2. Both 74HC595 ICs (U3 and U4)
3. ULN2001D ICs (U5, U6, U7 and U8)
4. All SMD resistors and ceramic capacitors
5. Resistor networks (RN1 and RN2)
6. AMS1117-5.0 voltage regulator (U1)
7. Through-hole type Electrolytic capacitors
8. JST connectors (J2, J3 and J4)
9. ISP connector (J12)
10. Relays (RL1 to RL12)
11. Screw terminals