Incident Com Tech. diagnosed the KNG charging unit and found the following:
U2 is a Voltage Regulator IC WS 78L05. It has an output voltage of 5V with an input of 12V and can handle an output of 100mA. It is known for excessive heat loss. Possible reasons for overheating can be one or a combination of any of the following:
1) Output current exceeded component parameters.
2) Heat loss of component with addition of ambient temperature exceeded component’s normal operating temperature parameters.
3) Defective, bad batch of components, or lower grade component installed.
4) Poor design due to not having a heat sink installed or installation of higher current capable component such as WS 7805.
U7 is a MOSFET IRFg530N. It’s shorted between Gate, Drain, and Source with 0V applied (power off). No change with power.
1) Using infrared Thermal Camera found Heat source spreading from U2 to R2 (1K ohm resistor) and spreading throughout traces of Printed Circuit Board (PCB) registering heat at ~150 F. Secondary side also showed heat behind and around Gate lead of U7.
2) PCB secondary side is delaminated and bubbled on other side of U7.
3) Inductor lead on secondary side has no solder. |
