Measurement of P27 4 feet without STB5V output that failure in auxiliary power supply parts, the voltage controlled by Q552 IC501 16 feet, Q537, Q538 output. Measuring IC501 work of several conditions, power supply, reset, is normal crystals. Eight feet of protection detection, 19 feet (normal work for low level), 19 feet (undervoltage protection detection,) has been as high level, in the protection state. IC411, IC410 IC403 Q427, Q408 for undervoltage protection circuit, etc. Measuring IC411 serious about 3 feet in 2 v voltage swing, measuring the resistance R445, R446, R447 normal, measuring zener diode D402 reverse resistance, have leakage for 20 k. Normal after replacement.ZQxservice manual download site