Hi I am having some trouble with with a seemingly simple circuit (see attachment 1). I am using a N-channel MOSFET to control power to a wireless bridge connected to connector X5. If JP4 is left open, the gate of the FET is pulled high by resistor R36, and the FET is turned on allowing power to flow to the wireless bridge. If pins 1 & 2 on JP4 are jumpered together, the gate of the FET is pulled to GND and the FET should turn off, causing the wireless bridge to turn off. However, this does not seem to be the case. When I jumper pins 1 & 2 together on JP4 the FET does NOT turn off, and the bridge remains on. This seems like a very simple circuit to me, but maybe I am missing, or overlooking something. I have checked the gate pin with a voltmeter and scope to ensure that it was actually at ground when JP4 is jumperd. Everything seems to check out but the FET does not seem to want to turn off. Does anyone have any Ides on what may be causing this or what I may be overlooking?
Also on the same 18V line in this circuit is the input side of a DC-DC converter that supplies other voltages to other parts of the circuit, (see attachment 2) I am wondering if these could affect anything?
Thanks for your help,
Charlie