[SOLVED]820-3435 Fan spinning on high

ytesfay80

Member
I have this liquid damaged machine. Initially the fan spun very fast and was making the 3 beeps Ram sound. I took the machine apart and noticed the underside of the fan was sticky and had liquid damage.
After the board was ultrasonic'd the machine boots fine now but the fan issue remained. In ASD the fan was the only thing to fail.
I even tried plugging in a fan from a 13" Air but that still did the same thing.

I put the board under a microscope and noticed that Q6060 was missing from the board so i put another one on it but still the fans spin on high immediately after the charger is plugged in.
Here are some voltages I get from that area.
R6061 Pin 1 - 3.32v Pin 2 - quickly pulses around 0.85v but then stays at 0.05v
R6065 Pin 1&2 - 1.62v
R6060 Pin 1 - 3.32v Pin 2 - 1.61v

J6000
Pin 1 - 5.1v
Pin 2 - 1.62v
Pin 3 - 4.63v
 

dukefawks

Administrator
Is fan RPM correctly displayed in ASD profile? R6065 checked? Diode mode on the tach line? crap under SMC possible too.
 

ytesfay80

Member
Diode mode of TACH (Pin 2 of J6000) is 0.635v

I have the voltage measurements of R6065 above and the resistance of it shows 43.5kohms

I attached an image of the RPM profile. I believe the reading was 6131 RPM.
 

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dukefawks

Administrator
So the tach signal is working fine. So your problem must be around Q6060 as the setpoint is 1200. Check SMC_FAN_0_CTL and check traces to/from Q6060 and possibly another Q6060.
 

ytesfay80

Member
I checked the traces that go from Q6060 and all of them were fine. I put another Q6060 and R6061 on the board but still the same issue remains.
I measured SMC_FAN_0_CTL on pin 2 of R6061 and it still just pulses very quickly at around 0.85v then just stays at 0.05v. Pin 1 of R6061 is a steady 3.32v.

Could it be an issue with the fan or the fan connector?
 
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ytesfay80

Member
I tried with a fan from a 13" Macbook and it does the same thing. Are those fans compatible or do I need to get a fan for an 11" machine?
 

ytesfay80

Member
Okay I put flux on the SMC and heated it up but not to the point of it being reflowed. Also, when I looked around the corroded JTAG connector that I previosly removed I noticed that R6115 was missing from the board so I may have knocked that off when I initially removed the JTAG. I put R6115 back on the board but the fan issue still remains.

Here are some measurements I got now.
SMC_FAN_0_CTL on Pin 2 of R6061 is a steady 3.41v. Before it would only pulse initially at 0.85v and then stay at 0.05v.

FAN_RT_PWM is a steady 4.65v
Pins 1/2 of R6065 is still around 1.65v
 

dukefawks

Administrator
Run ASD again and check fan speed and set point again. If set point is at 1200RPM and SMC_FAN_0_CTL is at 3.41V then something is pulling up that line. So either something with Q6060 or the SMC.
Check resistance between SMC_FAN_0_CTL and PP3V42.

I assume there are no sensor errors in ASD!
 

ytesfay80

Member
I ran ASD and there were no errors except on the fan section. The setpoint said 1200rpm and the speed was 6059rpm. I checked SMC_FAN_0_CTL and it was again showing 0.05v. What voltage should it be at?

Resistance between SMC_FAN_0_CTL and PP3V42_G3H is around 218 kohms

I just measured SMC_FAN_0_CTL a couple more times and its back to doing the pulsing 0.85v and then stays at a steady 0.05v.
 
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dukefawks

Administrator
SMC_FAN_0_CTL is correct at pretty much 0V. SMC is seeing 6000RPM so it will try and bring that down. Still there is a Q6060 problem because it's output is stuck at 4.65V. Compare voltages to a known good board and inspect the traces to Q6060.

Edit:

Actually that is wrong it is an N-channel so if gate is low it will be fully on. Check diode mode on SMC_FAN_0_CTL and check if the pull up resistor R6061 is good and traces.
 
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ytesfay80

Member
Thanks duke the issue was in fact Q6060. I removed it and noticed one of the pads on the chip were gone and the same thing happened with 2 more chips that I pulled from donors. I found a clean one and now the fan is working as it should.

Thanks you can mark this as solved.
 
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