Dell Latitude 3350 mb: RoundRock MB 15203-1 JM7HC REV:A00 The fan is not working

[anty]

Hi,

Fan replaced - not working

U2601 replaced
n.1 0V
n.2 3,3V
n.3 5V
n.4 3.3V
n.5 3.3V
n.6 0V

[ktmmotocross]

Re: Dell Latitude 3350 mb: RoundRock MB 15203-1 JM7HC REV:A00 The fan is not working

without schematic or ic marking u will have tons of helpers

[anty]

Re: Dell Latitude 3350 mb: RoundRock MB 15203-1 JM7HC REV:A00 The fan is not working

U2601 (2n7002kdw)

[mcplslg123]

Re: Dell Latitude 3350 mb: RoundRock MB 15203-1 JM7HC REV:A00 The fan is not working

2N7002KDW-Pin1 and Pin4 is Ground. So your readings are not correct. perhaps counting in the wrong direction.

[anty]

Re: Dell Latitude 3350 mb: RoundRock MB 15203-1 JM7HC REV:A00 The fan is not working

2N7002KDW-
Pin1 - FAN1-PWN

Pin4 - FAN1 TACH FB

[mcplslg123]

Re: Dell Latitude 3350 mb: RoundRock MB 15203-1 JM7HC REV:A00 The fan is not working

2N7002KDW-
Pin1 - FAN1-PWN

Pin4 - FAN1 TACH FB

Do you have the schematic??

[anty]

Re: Dell Latitude 3350 mb: RoundRock MB 15203-1 JM7HC REV:A00 The fan is not working

Do you have the schematic??

I don't have a schematic. Information searched on the internet

[mon2]

Re: Dell Latitude 3350 mb: RoundRock MB 15203-1 JM7HC REV:A00 The fan is not working

Post a clear picture of U2601 component. It does not appear in what I believe is the schematic for this laptop.

Any markings on the logic board to assist you further ?

[anty]

Re: Dell Latitude 3350 mb: RoundRock MB 15203-1 JM7HC REV:A00 The fan is not working

https://www.elvikom.pl/pictures/00055011.jpg

KBC MEC5085-LZY-6

[mon2]

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.

[anty]

Re: Dell Latitude 3350 mb: RoundRock MB 15203-1 JM7HC REV:A00 The fan is not working

1) Check your thermal sensors.

HWinfo It shows 55C during take-off.

OCCT during 62C temp test and rising


I have already tested the short circuit of pins 1 and 2. The fan worked 100%

But how I desoldered the mosfet (2N7002), and the voltage on pin 1 (U2601) started to jump

3) You may have to reflash the MEC5085 as it is integral to the fan & thermal sensor operations.

there will be a problem with programming no load

[mon2]

Re: Dell Latitude 3350 mb: RoundRock MB 15203-1 JM7HC REV:A00 The fan is not working

1) is the replacement mosfet known good and is the same part # ?

2) what is the pwm voltage with mosfet removed?

3) be sure the 5v0 pull up resistors are present at r2530 and r2529.

4) what is tach fb voltage with and without the mosfet?

[anty]

Re: Dell Latitude 3350 mb: RoundRock MB 15203-1 JM7HC REV:A00 The fan is not working

1) is the replacement mosfet known good and is the same part # ?

changed to the same

2) what is the pwm voltage with mosfet removed?

pin 1 (1.1V - 2.4V) but only the second time the laptop is turned on.

- disconnect the power supply
- I will connect the power supply
- and after turning it on for the second time, the board shows voltage

3) be sure the 5v0 pull up resistors are present at r2530 and r2529.

R2530 2.2kohm
R2529 2.2kohm

4) what is tach fb voltage with and without the mosfet?

pin 4 3.3V with
3.3V without

[mon2]

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.

[anty]

Re: Dell Latitude 3350 mb: RoundRock MB 15203-1 JM7HC REV:A00 The fan is not working

Everything is new.

What resistor to put on the 5V line to lower, for example, to 3V

[mon2]

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.

reference:
https://www.arduino.cc/en/Tutorial/Foundations/PWM

Using the resistors as a voltage divider method is just driving out a pure analog signal which will not be the same.

A multimeter is unable to detect the rapid fall time of the digital pulse train so it will measure as a voltage with varying values.

The resistor based voltage divider details are posted on many websites including this one:

https://www.allaboutcircuits.com/too...er-calculator/