Alarm clock with hygro-/thermometer, red, 18x6x7 cm

1. Battery cover
   1. Loosen 2× M2×7 captive screws
   2. Remove the part
2. Battery holder and rear button plate
   1. Remove 5× ST1.7×6 screws
   2. Lift up the part
   3. Insert a long screwdriver e.g. a test pen to push on one of the retaining tabs on the rear plate
   4. Pull upwards on the corner to free it (do not pull too hard to avoid breaking the other tab that is still engaged)
   5. Push on the remaining retaining tab while pulling upwards to free it too (be careful not to re-latch the other tab)
   6. Remove the part
3. Power board
   1. Remove 4× ST1.7×6 screws
   2. Lift up the part and flip it over to the bottom side of the board to free it
   3. The part cannot be removed fully as the wires are soldered on both ends
4. Mid-frame
   1. De-route the power cord from the cord grip
   2. Remove 6× ST1.7×6 screws
   3. Remove the part
5. Main board
   1. Remove 8× ST1.7×6 screws
   2. Lift up the part and free it
   3. The part cannot be removed fully as various wires are soldered on both ends

• U6 is an unmarked IC (SOIC-16N package) and likely an 8-bit MCU running the show
  • Pin 3 ↔ VPP testpoint
  • Pin 4 ↔ CLK testpoint
  • Pin 7 ↔ GND
  • Pin 11 ↔ SDA
  • Pin 12 ↔ SCK
  • Pin 14 ↔ Buzzer
• U1, U2, U4 are VINKA VK1640 (SOP28 package) LED drivers
• U3 is an unmarked IC (TSSOP-24) and likely an RTC
  • Pin 2 ↔ GND
  • Pin 14 ↔ CK testpoint
  • Pin 15 ↔ 32.768 kHz crystal
  • Pin 16 ↔ 32.768 kHz crystal
  • Pin 23 ↔ V
• Photodiode for automatic brightness
• Sensors in the clock leg with a vent
  • Analog humidity sensor
  • Analog thermistor
  • Buzzer on this external sensor PCB