Xbox 360 No Power

Xbox 360 No Power

No PowerEdit

Board is unresponsive to power button

Undo Bad Writes/Check For Faulty NAND

  • The board cannot power on if it cannot load a valid SMC and config from the NAND flash
  • Read NAND and check that the dump is valid
  • If you cannot get valid flash config, continue to next step
  • Replace NAND if flashing a valid image does not yield a valid read
  • Some 4GB Coronas may have a faulty Phison (V2) or eMMC (V4/V6) chip, they must be replaced or downgraded to 16MB
    • This is a common fault, where the controller wears out with extended use of the internal 4GB MU
    • Usually the system will stop saving settings or updating before going completely dead due to controller degradation
    • Can be diagnosed by attempting read/write
    • If faulty, replace Phison/eMMC (U1E3) or convert the board to 16MB
      • Ensure to program the correct image afterwards
      • If the image could not be read/decrypted before replacing, boot XeLL to grab the CPU Key and LDVs and rebuild the image

Standby Power Rails

  • Check for correct voltage and no short circuit in the following order:
Power Rail Source Location: Phat Location: Trinity Location: Corona
V_5P0STBY Standby 5V directly from PSU FT8N1 FT6M1 FT6M1
V_5P0DUAL 5V, switched between V_5P0STBY and V_5P0 FT1R2 FT1N9 FT1N9
V_3P3STBY 3.3V, created from V_5P0STBY FT5N1 FT5M1 DB5A2
V_1P8STBY 1.8V, created from V_5P0STBY FT5N2 FT5N2 N/A
V_1P2STBY 1.2V, created from V_5P0STBY N/A N/A DB3C2

Missing V_5P0STBY:

  • This rail comes directly from the PSU. Check DC jack:
    • Phat: J9A1 Pin 8
    • Slim: J7A1 Pin 10
  • Check for shorted filtering caps for V_5P0STBY:
    • Phat: C5B7, C8B1, C9A4
    • Slim: C6A1, C6A4, C6A5

Missing V_5P0DUAL:

  • This rail comes from either V_5P0 or V_5P0STBY, depending on VREG_V5P0_SEL
  • Check regulator pins 5-8 for 5 volts:
    • Phat: U1R1
    • Slim: U1B1
  • Check front and rear USB port pins are not shorted or damaged
  • Check VREG_V5P0_SEL is high (so that V_5P0DUAL will be created from V_5P0STBY)
    • Phat: FT1R1
    • Trinity: FT1P1
    • Corona: FT2R1
  • Check 4.75K Ohm resistor:
    • Phat: R1D6
    • Slim: R1P1
  • If VREG_V5P0_SEL is still missing, replace Southbridge:
    • If VREG_V5P0_SEL is still missing, proceed to the SMC Reset step

Missing V_3P3STBY:

  • Phat:
    • If U5B1 circuit is present:
      • Check U5B1 regulator for shorts, NCP1117 or compatible
      • Check C5B1, C5B2 for shorts
    • If U9C1 circuit is present (Some Phat Jasper Kronos only)
      • Some boards use this different circuit, manufacturer choice, U5B1 circuit will not be present
      • Check U9C1 regulator for shorts
      • Check R9C5: 0 Ohms
      • Check C9C8, C9C10 for shorts
  • Trinity:
    • Check U5A1 regulator for shorts
    • Check R5A11: 0 Ohms
    • Check C5A1, C5A2, C5A3 for shorts
  • Corona:
    • Check U5A1 regulator for shorts
    • Check R5A8, R5A12: 0 Ohms
    • Check C5A1, C5A2, C5A3 for shorts

Missing V_1P8STBY:

  • Phat:
    • If U5B2 circuit is present:
      • Check U5B2 regulator for shorts, NCP1117 or compatible
      • Check C5B4, C5B6 for shorts
    • If U9D1 circuit is present (Some Phat Jasper Kronos only)
      • Some boards use this different circuit, manufacturer choice, U5B2 circuit will not be present
      • Check U9D1 regulator for shorts
      • Check R9D4: 0 Ohms
      • Check C9D5, C9D9, C9D10, C9D11 for shorts
  • Trinity:
    • Check U5B1 regulator for shorts
    • Check R5B4: 0 Ohms
    • Check C5B1, C5B2, C5B6, C5B7 for shorts
  • Corona: See below, uses V_1P2STBY instead

Missing V_1P2STBY:

  • This rail exists only on Corona and is a replacement of V_1P8STBY
  • Check U5A2 regulator for shorts
  • Check R5B4, R5A13: 0 Ohms
  • Check C5A9, C5B1, C5B2, C5B3, C5B7 for shorts

SMC Reset

  • SMC_RST_N must go high in order for the SMC to run
  • It is controlled by ANA/HANA (integrated in Southbridge for Corona)
  • Check that SMC_RST_N goes high (3.3V):
    • Phat: J2B1 Pin 5
    • Slim: J2C3 Pin 5
      • Corona: If R2C10 is missing, check R2C10 S Pad instead, resistor is not needed
  • If missing signal:
    • Phat:
      • Check R2P18: 100 Ohms
      • Check R2P1: 10K Ohms
      • Check R2P3: 1K Ohms
      • Check C3P9 for shorts
    • Trinity:
      • Check R3R13: 100 Ohms
      • Check R3R15: 10K Ohms
      • Check R3R16: 1K Ohms
      • Check C3R2 for shorts
    • Corona:
      • Check R2C10: 100 Ohms
      • Check R3P15: 10K Ohms
      • Check R3P16: 1K Ohms
      • Check C2P51 for shorts
  • If still missing signal:
    • Xenon: Replace ANA U4C2
    • Zephyr, Falcon, Jasper: Replace HANA U4C2
    • Trinity: Replace HANA U3B1
    • Corona: Replace Southbridge U3D1

Standby Clock

  • STBY_CLK is created by the ANA/HANA and is used to run the System Management Controller (8051 core) in the Southbridge
  • Phat/Trinity:
    • Check STBY_CLK for 48 MHz single-ended clock:
      • Phat: FT2R2
      • Trinity: FT3N2
    • If bad/missing signal:
      • Check master crystal Y3B1 for 27 MHz single-ended clock
      • Check STBY_CLK resistor for 33 Ohms:
        • Xenon: R3B7
        • Zephyr, Falcon, Jasper: R4B24
        • Trinity: R3B15
      • Replace clockgen chip:
        • Xenon: Cypress CY28517 U3B4
        • Zephyr, Falcon, Jasper: HANA U4C2
        • Trinity: HANA U3B1
  • Corona:
    • These boards do not have a STBY_CLK signal as the clockgen was integrated with the Southbridge (KSB), it is generated internally
    • Check master crystal Y3D1 for 25 MHz single-ended clock
    • This is as far as we can check STBY_CLK circuit on these boards


  • If all else fails, Southbridge is bad and must be replaced:
    • Phat: U2C1
    • Slim: U3D1


Original article credit: Octal450