2. Criticality measures Low  General annoyance – screen stops working, buttons don’t work  λ < 10 -5 High  Parts get hot, catch fire, and/or explode  λ < 10 -9

3. Battery Pack – “A”

4. Failure No.Failure ModePossible Causes Failure EffectsMethod of Detection CriticalityRemarks A1Header Output Battery Disconnected, Battery dead, Protection circuit failure Device is inoperable ObservationLow 1 = 0V A2Header Output U19 failure, R74 damaged, Unable to track battery life via uC, in the cases of U19, R74 failure ObservationLow 2 = 0VBattery dead A3Battery Shorted out Traces in battery circuit short out, wiring from battery terminals short out Battery discharges VERY rapidly (Protection circuit keeps from exploding) ObservationHigh A4Header output 1 > 8.4V Protection circuit failure Battery becomes overcharged, can lead to overheating, possibly explosion ObservationHigh

5. 3.3V Regulator – “B”

6. Failure No.Failure ModePossible Causes Failure EffectsMethod of Detection CriticalityRemarks B1PWR_3.3 < 3.3V U20 failureCircuit becomes underpowered, device is inoperable ObservationLow B2PWR_3.3 > 3.3V U20 damagedOther components in circuit could be damaged by overvoltage ObservationHigh B3PWR_ON+ > 14.4V Short in SW4 between PWR_ON+ and PWR_OFF+, along with a failure of U18 Damage to U20, can lead to B2 happening ObservationHigh

7. Battery Recharger – “C”

8. Failure No. Failure Mode Possible Causes Failure EffectsMethod of Detection CriticalityRemarks C1PWR_OFF+ <8.4V Wall Wart disconnected, R76, R75 or, R70 short Battery won’t charge completely ObservationLow C2PWR_OFF+ >8.4V U18 Damaged, short in recharger, R76, R75, or R70 damaged Battery runs the risk of being overcharged if protection circuit has failed ObservationHigh C3Conn Jack Pwr input >21V Power surge from outlet U18 damagedObservationHigh

9. Compact Flash Circuit – “D”

10. Failure No. Failure Mode Possible Causes Failure EffectsMethod of Detection CriticalityRemarks D1No transmission from CompactFla sh card CF card disconnected or loose, PWR disconnected, software error TetriNET will not be playable online. ObservationLow

11. Microcontroller Circuit – “E”

12. Failure No.Failure ModePossible Causes Failure Effects Method of Detection CriticalityRemarks E1Continual resetting Y1, C26, C27 – problem with the crystal circuit Device will be inoperable ObservationLow E2Timer overflow A game of TetriNET lasts longer than 6.362915 days Code will have erratic effects ObservationLow

13. Button Circuit – “F”

14. Failure No. Failure Mode Possible CausesFailure EffectsMethod of Detection Criticalit y Remark s F1Buttons don’t register inputs BTN_SEL not changing, U17 damaged, button wiring loose Device cannot be properly operated ObservationLow

15. LCD Circuit – “G”

16. Failure No. Failure ModePossible CausesFailure Effects Method of Detection CriticalityRemarks G1Displays nothing U4/U5 connectors damaged or loose, ezLCD-001 damaged Device cannot be used ObservationLow G2Displays gibberish Software error, ezLCD- 001 damaged, header connections not complete Device unstable or unusable ObservationLow

17. Reprogramming Circuit – “H”

18. Failure No. Failure ModePossible CausesFailure EffectsMethod of Detection CriticalityRemarks H1Circuit cannot be reprogrammed U9/U10 damaged or loose Cannot reprogram microcontroller ObservationLow