ROCKPro64 pwm-fan inoperable
01-01-2020, 10:37 AM
(This post was last modified: 01-01-2020, 01:20 PM by resistanceisfutile.)
UPDATE:
Scope fixed. PWM is present at the base of Q2110 with peaks around 700mV. Disabled the CPU thermal zone to keep PWM consistent for further testing. D2101 is not present on this board and from the high res images on the website, this diode is also not present. Appears to be for reverse polarity protection.
When using the oscilliscope, I noticed that the fan starts spinning and responding to different PWM widths when the probes are touching pin 1 (+) of the fan connector and pin 3 (collector) of Q2110. Unfortunately, I saw R89554 briefly turn into an LED before releasing the magic. Likely due to exceeding maximum current rating by accidentally completing the circuit between VCC12V_DCIN through the resistor and then through Q2110 collector<->emitter to ground.
In conclusion - the fan driving circuit (R89554, R2, Q2110, D2101 (not present)) seems suboptimal, and possibly doesn't work with some fans? Mind you, this fan is the one purchased from pine store for use in the NAS case.
I can wire the fan directly to 12V but would prefer not to. Replacing the dead component(s) should be easy enough, but it's still a mystery why this circuit does not work.
See page 6:
http://files.pine64.org/doc/rockpro64/ro...21-SCH.pdf
Scope fixed. PWM is present at the base of Q2110 with peaks around 700mV. Disabled the CPU thermal zone to keep PWM consistent for further testing. D2101 is not present on this board and from the high res images on the website, this diode is also not present. Appears to be for reverse polarity protection.
When using the oscilliscope, I noticed that the fan starts spinning and responding to different PWM widths when the probes are touching pin 1 (+) of the fan connector and pin 3 (collector) of Q2110. Unfortunately, I saw R89554 briefly turn into an LED before releasing the magic. Likely due to exceeding maximum current rating by accidentally completing the circuit between VCC12V_DCIN through the resistor and then through Q2110 collector<->emitter to ground.
In conclusion - the fan driving circuit (R89554, R2, Q2110, D2101 (not present)) seems suboptimal, and possibly doesn't work with some fans? Mind you, this fan is the one purchased from pine store for use in the NAS case.
I can wire the fan directly to 12V but would prefer not to. Replacing the dead component(s) should be easy enough, but it's still a mystery why this circuit does not work.
See page 6:
http://files.pine64.org/doc/rockpro64/ro...21-SCH.pdf