MOS tube problem

chenbingjy

MOS tube problem [Copy link]

As shown in the figure, VABT3.9V, 203C EN 3.3v, R17 upper end 3.6V. C22 both ends 0.8V. The multimeter measured the resistance value of R16 is very small. What's going on? Thank you!

xunke

Did you test correctly with the multimeter probe?

maychang

"The resistance value of R16 measured by the multimeter is very small. What's going on?" It is very likely that the gate of the MOS tube has been broken down and damaged.

qwqwqw2088

PMOS tube si2305 is not conducting,,,, R16 is 100K, the value is very small,,

chunyang

How small is "very small"? What gear? If you measure online, the digital meter should use the diode gear and swap the test leads to measure twice, while disconnecting the power supply and external devices. If the values measured twice are very small, it can be determined that the MOS tube gate is broken down. From the voltage measurement value, either the MOS tube has a problem, or the resistance value of R16 is incorrect. Also pay attention to whether the wrong MOS tube pin is used.

chenbingjy

xunke posted on 2018-1-2 14:50 Did you measure the multimeter probe correctly?

Yes.

chenbingjy

qwqwqw2088 posted on 2018-1-2 15:08 PMOS tube si2305 is not conducting,,,, R16 is 100K, the value is very small,,

100 ohm

chenbingjy

chunyang posted on 2018-1-2 15:17 How small is "very small"? What gear? If you measure online, the digital meter should use the diode gear and swap the probes to measure twice. At the same time, the power supply and external devices must be disconnected...

Chunyang is amazing. R16 was soldered incorrectly and it became 100 ohms.