A preliminary judgment fault in the timer operation or control circuit. Open the case, in a stopped state IC7501 were examined with a model 500 multimeter/MNI4824VTU feet of voltage, found 13 ~ 16 feet (data output voltage of 0 V, normal should be 4.8 V, check 17 ~ 20 feet (timer data) are the high level of 4.2 V, normal should be 0 V, oscilloscope were observed 13 ~ 16 feet no key scanning negative pulse signal output. Oscilloscope probe will be moved to the 4.1175 MHz clock oscillation signal normal 36 feet observation, 25 feet only 0.3 V voltage, normal is 4 V, to show that the fault IC7502 internal and peripheral circuits. Check the IC7502 feet of voltage, found 9 feet voltage of 1.4 V, adjust VR7502 to maximum, meter instructions for 3 V, normal should be 5 V. Unplug the power plug to check IC7502 each foot in the right way to resistance, found eight feet only 22 Ω, 9 feet is 34 Ω, normal Ω Ω should be 4.8 k and 4.8 k, touch IC7502 seriously hot surface, explain IC7502 (AN5033) within 5 v detection has been broken down and delay circuit, thus causing the output signal loss IC7502 12 feet RST and appear the fault phenomena, with integrated AN5033 replaced and troubleshooting.5mSservice manual download site