Problem in 5V Fan

[magneh]

Hello!

I've got a laptop with fan problem. Doesnt turn.

Here's the circuit.

On U41 I've got :
Pin1 - 1.44V
Pin2 - 5.14 V
Pin3- 0.03V
Pin 4 - 0.01V

On JFAN :
pin1 - 0.02V
pin2-GND
pin3 - 3.25V

U41 is the culprit?
Didnt find any shorts.

Thanks for your help!

[stj]

Re: Problem in 5V Fan

take the fan out and test it.
they often jam or need to be stripped & lubed.

[magneh]

Re: Problem in 5V Fan

The fan is OK

And she works, I've applied 5V to her and works perfectly

[pravin6p]

Re: Problem in 5V Fan

change the circuit. take 5 volt from the usb.
its easy. thats what i do in this case.

[atsio]

Re: Problem in 5V Fan

Hello!

I've got a laptop with fan problem. Doesnt turn.

Here's the circuit.

On U41 I've got :
Pin1 - 1.44V
Pin2 - 5.14 V
Pin3- 0.03V
Pin 4 - 0.01V

On JFAN :
pin1 - 0.02V
pin2-GND
pin3 - 3.25V

U41 is the culprit?
Didnt find any shorts.

Thanks for your help!

You are not measuring something allright. You can't have 5v on pin 2 of U41 and 0.02v on pin1 of JFAN and no shorts.

[stj]

Re: Problem in 5V Fan

check the ceramic capacitors for shorts.

[magneh]

Re: Problem in 5V Fan

You are not measuring something allright. You can't have 5v on pin 2 of U41 and 0.02v on pin1 of JFAN and no shorts.

Hello!

https://cdn.badcaps-static.com/pdfs/...a2fa5bebc3.pdf

Humm... I think the pin2 of U41 is Vset, and then nothing to do with pin of JFAN

JFAN pin1 = Pin 3 U41 ( Vout = 1.6x Vset pin 4)

I think the problem is having 0V at pin 4 Vset

If I had 3V there the 5V would appear on pin 3 of U41.
I've mesured on D40 3.25V

I've also noticed that I have what seems to be a burned component (see photo attached )
It's PR128 I think ...

The laptop had also problems in keeping CMOS settings , but the battery is OK (2.9V)
Where could I find a similar component to change this one? on a broken laptop rig I suppose ?

thanks again!

[atsio]

Re: Problem in 5V Fan

Yes you are right. Quick answer without paying much attention to the schematic (too busy). What's the model of the board?

[stj]

Re: Problem in 5V Fan

that looks more like soldering residue from an iron.

[Agent24]

Re: Problem in 5V Fan

I think the problem is having 0V at pin 4 Vset

If I had 3V there the 5V would appear on pin 3 of U41.

I think so too. Note that Pin 1 (/FON) will turn fan on full if pulled low, I would try that, if it starts the fan, find out why you aren't getting CPU_FAN signal to Pin 4, if it doesn't, maybe U41 is dead.

[atsio]

Re: Problem in 5V Fan

The shematic (picture) points it clearly that they are shorted pads and I don't think it has to do anything with the EN signal of the fan because it is to boost the voltage of a voltage regulator and from what I understand from the picture it has to do with the 1.8v regulator.
What is the model of your board?

[magneh]

Re: Problem in 5V Fan

Hello again!

Back

Here's the model : 6-71-M74S0-D05A

The manual I found is the clevo w760s w765s model reference.

Tomorrow I'm gonna work on it.

Please leave your thoughts guys!

Thanks!

[magneh]

Re: Problem in 5V Fan

I think so too. Note that Pin 1 (/FON) will turn fan on full if pulled low, I would try that, if it starts the fan, find out why you aren't getting CPU_FAN signal to Pin 4, if it doesn't, maybe U41 is dead.

UPDATE

Ive pulled low Pin1 and the Fan started spinning immediately!

Mesured the resistance in R586 and I read 1170 ohms...

[Agent24]

Re: Problem in 5V Fan

That R586 is probably OK, and I guess so is U41. They aren't going to pull it down hard with a low value resistor and lose control over the fan. Most likely CPU_FON# signal is normally pulled high and goes low when they want the fan at 100%

Though I don't understand what the *0_04 means on the schematic for R586.

Can you post the full schematic file to find out where these signals go, especially CPU_FAN?

[magneh]

Re: Problem in 5V Fan

That R586 is probably OK, and I guess so is U41. They aren't going to pull it down hard with a low value resistor and lose control over the fan. Most likely CPU_FON# signal is normally pulled high and goes low when they want the fan at 100%

Though I don't understand what the *0_04 means on the schematic for R586.

Can you post the full schematic file to find out where these signals go, especially CPU_FAN?

Hello!

Of course I can! Here he is.
Please share your thoughts! and thanks for your help!

[Th3_uN1Qu3]

Re: Problem in 5V Fan

I can answer that. Check R308. See if you get different voltages at each end of R308. If you aren't getting anything on either side, follow the trace from R308 to pin 76 of U20 IT8512E.

If there's nothing on pin 76 either, then U20 is faulty and must be replaced. But i wouldn't bother with that for a fan... You can easily make a little replacement circuit to enable the fan to still be thermally controlled.

[magneh]

Re: Problem in 5V Fan

I can answer that. Check R308. See if you get different voltages at each end of R308. If you aren't getting anything on either side, follow the trace from R308 to pin 76 of U20 IT8512E.

If there's nothing on pin 76 either, then U20 is faulty and must be replaced. But i wouldn't bother with that for a fan... You can easily make a little replacement circuit to enable the fan to still be thermally controlled.

Okay!
Gonna check that tomorrow.
Could this IC be also responsible for the problem in keeping the CMOS settings? the bat is OK but the laptop doesnt keep the setting when unplugged.
If it's U20 the culprit, could you explain to me how to enable the fan garanteeing the thermal control?

Thanks again!

[stj]

Re: Problem in 5V Fan

cmos problem is probably a bad diode

[Agent24]

Re: Problem in 5V Fan

I don't know how the fan controller works but I just thought of something, maybe the controller is getting bad feedback from the fan RPM sensor and it thinks the fan is spinning when it's not or something.

[Th3_uN1Qu3]

Re: Problem in 5V Fan

Okay!
Gonna check that tomorrow.
Could this IC be also responsible for the problem in keeping the CMOS settings? the bat is OK but the laptop doesnt keep the setting when unplugged.
If it's U20 the culprit, could you explain to me how to enable the fan garanteeing the thermal control?

Thanks again!

Yes it could very well be U20. But also check the diodes and transistors connecting the RTC battery to U20 like stj suggested.

I don't know how the fan controller works but I just thought of something, maybe the controller is getting bad feedback from the fan RPM sensor and it thinks the fan is spinning when it's not or something.

Impossible, as this particular fan controller chip is a "dumb" model, it's just a linear regulator. RPM is not even monitored in most laptops for other than displaying it to some diagnostic software... The fan speed is based on the thermal sensors monitored by the EC which is U20 in this case.