D Board Sos Detect (Explanation) - Panasonic TH-42PX80U Service Manual

• Protection circuits are incorporated in the unit to prevent the failure of a single circuit
or component from creating catastrophic damage.
• A shutdown condition occurs when there is an over voltage, a short or a drop in any
of the voltage lines. Also the shutdown circuit is triggered when the fans are drawing
more current than normal.
• Normally the CPU of the D board and the CPU of the A board detect when a
shutdown condition has been triggered.
• When an abnormality has occurred, the unit protection circuit operates and the TV is
reset to the stand-by mode. At this time, the defective block can be identified by the
number of blinks of the POWER LED on the front of the unit.
• IC9003 of the D board detects conditions that make the power LED blinks 2, 3, 4, 5,
6, 7, 8, or 9 times.
• The following table identifies the areas where a problem is suspected according to
the number of times that the POWER LED blinks.
• 2 Blinks SOS:
operation pin 62 is kept high. If the 15V line is missing or shorted, a low is provided to
pin 62. As a result, the unit shuts down and the power LED blinks 2 times.
• 3 Blinks SOS:
monitored by IC9003. If the 3.3V is not present at pin 61, the CPU (IC9003) shuts
down the unit. The power LED blinks 3 times.
D board SOS Detect
Pin 62 of the CPU IC9003 monitors the 15V line. During normal
IC9805 is a 3.3V regulator located on the D board. Its output is
Panasonic
49
ideas for life
49