Re: Dell Latitude 3350 mb: RoundRock MB 15203-1 JM7HC REV:A00 The fan is not working
Ok. Found this cryptic labelled schematic in the database after searching assorted websites.
See attached for the hint to locate the same.
1) Check your thermal sensors.
2) The dual mosfet (2N7002) are acting like a level shifter between the 3v3 and 5V0 fan circuits.
3) You may have to reflash the MEC5085 as it is integral to the fan & thermal sensor operations.
4) Given that pin # 1 of the dual mosfet (FAN1_PWM) = 0V, the fan will remain OFF.
If you feel comfortable with the idea, consider to:
Lift up the leg of pin #1 of U2601 and apply 3v3 onto pin #1. Do not allow for the PCB pad that is connected to the MEC5085 to receive this manual fed 3v3 rail. The reason being that the MEC5085 pin for the PWM is also an output pin and presently it wants to send out 0V.
If you manually apply 3v3 onto pin #1 (only), believe that the fan should run @ 100%. As a test, confirm it and post your results.
Re: Dell Latitude 3350 mb: RoundRock MB 15203-1 JM7HC REV:A00 The fan is not working
With the posted temps, check that your heatsinks are doing their job. Very likely, you need to remove the old and apply fresh heatsink compound onto the CPU.
Check the reset circuits to the see their status when the pwm does not kick on.
Re: Dell Latitude 3350 mb: RoundRock MB 15203-1 JM7HC REV:A00 The fan is not working
Are you trying to emulate the missing PWM signal ?
Note that the PWM is a rise and fall of a digital signal from logic '0' to '1'. The duration of the '1' level defines the ON time for the target; '0' level defines the OFF time. Using this method, one could configure the intensity of a LED or motor speed, etc. For the motor speed, the wimpy logic levels have to be conditioned with the more powerful mosfets that can handle such heavier inductive loads.
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