Pioneer PDP-4270XA Service Manual page 95

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How to identify the cause of a power-down that is indicated by 2-times flashing
of the red LED
The cause of a power-down that is indicated by 2-times flashing of the red LED can be identified by performing the steps 1 to
3 below:
1 Visual check with the power off
2 Tester check with the power off
3 Check with the power on
1 Status check with the power off
Check if the cables and FFC cables that are connected to the Y DRIVE Assy are firmly connected.
2 Tester check with the power off
1. Check between Vsus and SUSGND with a tester
Disconnect all cables from the X and Y DRIVE Assys and check if there is short-circuiting between Vsus and SUSGND
in the X and Y DRIVE Assys.
• How to check if there is short-circuiting on the X DRIVE Assy:
If there is short-circuiting between Vsus and SUS OUT, and SUS OUT and SUSGND, the X Mask Module is damaged.
If they are not short-circuited, check other elements to see if they are short-circuited.
• How to check if there is short-circuiting on the Y DRIVE Assy:
If there is short-circuiting between Vsus and SUS OUT, and SUS OUT and SUSGND, the Y Mask Module is damaged.
If they are not short-circuited, check other elements to see if they are short-circuited.
• Check for short-circuiting in the Power supply.
Note that at the beginning of measuring with a tester, charging of an electrolytic capacitor may cause a phenomenon
like short-circuiting. However, the resistance will soon rise if there is no short-circuiting.
2. Check for short-circuiting between VH and PSUS with a tester
Disconnect the cables that connect the bridge connectors between the Y DRIVE Assy and upper and lower SCAN
Assys.
• If there is short-circuiting in the upper SCAN Assy, one of Scan ICs in the upper SCAN Assy is damaged.
• If there is short-circuiting in the lower SCAN Assy, one of Scan ICs in the lower SCAN Assy is damaged.
• If there is short-circuiting in the Y DRIVE Assy, a circuit in the Y DRIVE Assy is short-circuited.
If no short-circuiting is detected up to this stage, the power-down in question is proved not to be caused by short-
circuiting. Therefore, it is assumed that the power-down occurred because power had not been supplied to Vsus or
VH for some reason.
3 Check immediately after the unit is turned on before a power-down occurs.
If the Vsus voltage does not increase, the POWER SUPPLY Unit is in failure.
If the VH voltage does not increase, the VH DC/DC converter in the Y DRIVE Assy is in failure.
4 Check the PD detection circuit.
If no problem is detected in steps 1 to 3, a power-down occurred even though the voltage was normal.
Therefore, the PD detection circuit may be in failure.
By following the above procedures, the real cause of a power-down can be judged.
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