shorting collector and emitter of a laptop fan transistor

[solarium]

Hi everybody!
I got a small problem concerning a laptop fan. During the first 30 minutes (more or less) it didn't work properly: it only started spinning immediately after having turned my laptop on after a system shutdown caused by the excess of CPU temperature (excess of temperature obviously due to the "absence" of the CPU fan). But then once on, the fan kept spinning for about 10-20 seconds before stopping again. So, once again the CPU temperature started rising until the forced shutdown. This kind of process occurred 3-4 times in 30 minutes. In this time span, the CPU fan seemed to be in oblivion and only worked at very high temperatures.
After these 30 minutes the fan started working regularly, even for hours!

Explained this problem, someone told me that it could easily depend on cold joints and a reflow of some components would have been the best solution in these cases. But I don't have a hot gun and neither do people I know. So I preferred to do some tests that someone advised.
Then I managed to reset the bios but nothing changed. I forgot to say that in the first 30 minutes my motherboard often blinked (caps lock and num lock).
At last, I found a quicker solution: to short collector and emitter of a darlington transistor that controls the CPU fan:

Now, it would be very intesting to know any possible disadvantage of this choice, such as energy consumption, transistor lifetime (as well as the ones of the other components that might be affected by the permanent spinning of the CPU fan) and other issues that would arise.
Anyway, thanks to a very small piece of copper (the end of a wire) put between collector and emitter, I tested my laptop for a few hours and it seemed that the full-speed fan didn't cause any problem and CPU temperature was well below acceptable limits.
Strange as it may seem, the DDR fan didn't even turn on, perhaps because CPU was always "mild" and so processor didn't give any signal to let the DDR fan start spinning. But I did want even the DDR fan running, so I did the same trick of joining collector and emitter. Now, I have 2 fans at full speed but I need to remove the temporary piece of copper and make this modification definitive.
There is just 1 mm between the 2 pins, so someone suggested to add a drop of solder in-between (without copper or any other material). Is the best solution if I don't want to waste time to unsolder the transistor? Does it guarantee a good electrical conductivity (and then a constant short between collector and emitter)? It should be a micro solder. I got a WS-70DA soldering iron that is not very precise for this kind of tasks. But I am going to practice a little bit before soldering on my motherboard.

Other issue concerns the noise. With 2 fans spinning at full speed I got to wear something to protect my ears... For this reason, someone suggested to put a resistor in order to decrease a bit the speed of the fan. For a DC 5V 0.30A fan, how many ohms should I need? Consider that often the CPU fan spinned at high speed (though not full speed), when my laptop worked in normal conditions. So I cannot exagerate with the ohms. But where and how putting the resistor in such a small available space? And what kind of resistor? Only SMD resistors?

 

[kubeek]

Which connector are you referring to?

 

[cowboybob]

Welcome to ETO, solarium!

kubeek, I think he meant "collector".

solarium, to make any significant reduction in fan speed, you're going to need (probably) upwards of a 1/2 to 1W resistor (huge for your application), which will get quite warm.

You might consider testing to see if the controlling transistor is at fault.

 

[audioguru]

A resistor in series with a DC motor reduces its maximum current which reduces its maximum torque. But a motor needs to use plenty of torque to get started so with a resistor it might not start running.
Usually a DC motor speed is controlled with Pulse Width Modulation (PWM) which gives full current pulses for plenty of torque but with gaps between the pulses to slow the speed.

I think the fan on my pc starts backwards at full power for a moment to blow away the dust. Then it slows down to almost nothing.

 

[tunedwolf]

Then I managed to reset the bios but nothing changed. I forgot to say that in the first 30 minutes my motherboard often blinked (caps lock and num lock).

Did you just reset it back to factory defaults using the bios utility, or did you actually re-flash or update the bios? I have seen more corrupted bios chips over the years than I care to remember, Acer for some reason more than most. The fact that you have other strange behaviours going on like keyboard interaction, possibly even a random keyboard reset, given your description, and fan control issues would also suggest a corrupted bios

 

[KeepItSimpleStupid]

I just have to remind you that fans ingest dirt in their bearings making them hard to start. You do need to try to move the fans by hand when warm and cold and compare the friction.

 

[solarium]

.
You might consider testing to see if the controlling transistor is at fault.

OK! Having a simple digital tester and without unsoldering the suspicious transistor, what kind of tests would you recommend to do while the fan is spinning (and even immediately after the turning on of the motherboard) and while the motherboard is off?
I found this schematic diagram on the internet:

Which components should I check out? And how?

Did you just reset it back to factory defaults using the bios utility, or did you actually re-flash or update the bios? I have seen more corrupted bios chips over the years than I care to remember, Acer for some reason more than most. The fact that you have other strange behaviours going on like keyboard interaction, possibly even a random keyboard reset, given your description, and fan control issues would also suggest a corrupted bios

At first, I used the BIOS utility to set back the factory defaults, then with my laptop completely disassembled I disconnected the CMOS battery. Finally, I was asked to short a couple of pins for 30 seconds with motherboard off, so without Power supply, laptop battery and BIOS battery.
Components to short: JOPEN or capacitors C194 and C195 or diode D27 (Cathode and ground or anode and ground). See the following diagram:

Basically, when shorting JOPEN (or the other mentioned components) with all power removed, I should ensure that no residual power remains in capacitors that might maintain power to memory, preventing the bios settings from clearing.
Shorting the capacitors discharges any energy that might be stored in them.
But after these tests I would definitely exclude a corruption of the BIOS just because the problem is still on-going

I just have to remind you that fans ingest dirt in their bearings making them hard to start. You do need to try to move the fans by hand when warm and cold and compare the friction.

Yes, I've tried to notice any possible difference in terms of friction but all I can tell you is that warm and cold states don't change the fans' friction

 

[tunedwolf]

All this shorting of pins, removing the battery or using the bios utility to restore to factory defaults etc only removes the user settings, it does not affect the bios code. The actual bios code that is loaded at boot time provides, amongst other things, direct hardware access for your software, it also provides you with the bios utility screen listing all your settings. IF that code is corrupted in any way, the mainboard will not function as intended. My advise at this point is to download the bios update utility from the manufacturer along with the latest bios file for your laptop and then flash the bios. I have encountered on more than one ocassion dual bios chips so badly corrupted that I had to remove them from the mainboard and place them in my programmer in order to restore them. Only once you have reprogrammed/ flashed the bios and confirmed it has taken, can you rule it out as the cause of your issues.

 

[cowboybob]

OK! Having a simple digital tester and without unsoldering the suspicious transistor, what kind of tests would you recommend to do while the fan is spinning (and even immediately after the turning on of the motherboard) and while the motherboard is off?

Are you familiar with a DVM (Digital Volt Meter) or its equivalent? Your digital tester might be useful later (for checking the PWM signal, if present).

I'd suggest first checking (at PC startup) the signal (which will be either a DC value OR a PWM digital signal) at the Base ("B", or pin 1 of the transistor that you've identified as the fan "controller" device).

Testing with the MB off will reveal nothing.

Let us know what you find.

 

[solarium]

All this shorting of pins, removing the battery or using the bios utility to restore to factory defaults etc only removes the user settings, it does not affect the bios code. The actual bios code that is loaded at boot time provides, amongst other things, direct hardware access for your software, it also provides you with the bios utility screen listing all your settings. IF that code is corrupted in any way, the mainboard will not function as intended. My advise at this point is to download the bios update utility from the manufacturer along with the latest bios file for your laptop and then flash the bios.

OK, so the actual BIOS code could be corrupted. Thank you for you clear explanation. I thought that all those actions undertaken were enough to rule the BIOS out.
Last August I took a note of my BIOS version:
PHOENIX 4.06 30/09/2003
Ver. SMbios 2.3

HwMonitor detected my motherboard as a Clevo 4xx series

So I visited Phoenix website to update but I was redirected to esupport.com, a website providing bios updates with fees. Fees? I don't have any intention to spend even half a cent to update my BIOS!
Some years ago I freely updated BIOS but I remember that my system didn't like that update, so I restored the previous one. Evidently, my hardware really didn't need it.
After the reset I saw on the POST that the current BIOS version is the 4.0 release 6.0 (then a few lines below: bios revision 1.05).
Is there a way to get access to BIOS updates without paying, as it's always happened (as far as I know)?

Anyway, now I have my laptop completely disassembled and I just want to make some measurements to possibly detect a faulty SMD component.

Are you familiar with a DVM (Digital Volt Meter) or its equivalent? Your digital tester might be useful later (for checking the PWM signal, if present).

I'd suggest first checking (at PC startup) the signal (which will be either a DC value OR a PWM digital signal) at the Base ("B", or pin 1 of the transistor that you've identified as the fan "controller" device).

Testing with the MB off will reveal nothing.

Let us know what you find.

I got a digital multimeter GBC KDM-120, very cheap. Do you think it's enough realible?
So did you tell me to check the voltage at the base of transistor?
Ok, let me ask you a simple question that you may consider banal. The positive red probe should be connected to the pin where you want to check voltage. But the negative black probe should be connected to ground. How to identify the ground? Could it be a nearby pin? In my case, according to the above diagram of the fan circuitry, when I want to measure the voltage at the base and at the other pins, where can I take the ground and connect the black probe?

 

[solarium]

Are you familiar with a DVM (Digital Volt Meter) or its equivalent? Your digital tester might be useful later (for checking the PWM signal, if present).

I'd suggest first checking (at PC startup) the signal (which will be either a DC value OR a PWM digital signal) at the Base ("B", or pin 1 of the transistor that you've identified as the fan "controller" device).

Testing with the MB off will reveal nothing.

Let us know what you find.

I got a digital multimeter GBC KDM-120, very cheap. Do you think it's enough realible?
So did you tell me to check the voltage at the base of transistor?
Ok, let me ask you a simple question that you may consider banal. The positive red probe should be connected to the pin where you want to check voltage. But the negative black probe should be connected to ground. How to identify the ground? Could it be a nearby pin? In my case, according to the above diagram of the fan circuitry, when I want to measure the voltage at the base and at the other pins, where can I take the ground and connect the black probe?

 

[KeepItSimpleStupid]

I can't say anything about the meter. I'll assume it's battery powered. If not, yell.

The meter measures the difference between black (-) and Red(+). If red is more negative than black, the voltage measured will be negative.

Computers generally connect the reference of the 5 V supply to chassis ground. Check to make sure +5 reads +5 V within 10%.

 

[tunedwolf]

HwMonitor detected my motherboard as a Clevo 4xx series

Ok, if it is a Clevo laptop, look up the number on the label found on the bottom of your laptop and go to the Clevo support site and find your machine. Download the correct bios file and utility for it: https://www.clevo.com.tw/clevo_prodetail.asp?id=792&lang=en

Once upon a time, meaning 20 years ago, bios manufacturers (AMI, Phoenix etc) used to maintain copies of generic files for general mainboard use and make those publically available, however as the years rolled by, each machine mainboard became so customised to each manufacturer, that they now only provide those files to the mainboard manufacturer which allows them to tweak it to suit their respective hardware. You must obtain the bios file from the mainboard manufacturer or the laptop manufacturer

Oh and bios files are free as are drivers etc from the manufacturer. Stay away from these scam sites trying to sell you files.

 

[cowboybob]

... In my case, according to the above diagram of the fan circuitry, when I want to measure the voltage at the base and at the other pins, where can I take the ground and connect the black probe?

Red lead to the Base and black lead to the Emitter (which is attached to circuit ground, which is also probably chassis ground). Be sure to first remove your short.

Select DC on your DVM first. Check the voltage from power up and then for at least a few minutes thereafter. This signal might be PWM'ed (not DC), in which case select AC on the DVM or use your digital probe and listen for a rapid buzz. This buzz would change tone if and when the fan is called on to increase/decrease speed.

The basic point here is to look for signs of meter deflection (or the presence of a PWM signal) from two possible varying signal types (DC or AC). This indicates that the appropriate controller signal is being applied to the controller transistor but it is not responding and, thus, is defective.

If there is NO apparent signal on the base of the controller transistor, then you've got a much bigger problem and you might consider just putting up with your current working solution (however annoying).

 

[solarium]

Ok, if it is a Clevo laptop, look up the number on the label found on the bottom of your laptop and go to the Clevo support site and find your machine. Download the correct bios file and utility for it: https://www.clevo.com.tw/clevo_prodetail.asp?id=792&lang=en

Once upon a time, meaning 20 years ago, bios manufacturers (AMI, Phoenix etc) used to maintain copies of generic files for general mainboard use and make those publically available, however as the years rolled by, each machine mainboard became so customised to each manufacturer, that they now only provide those files to the mainboard manufacturer which allows them to tweak it to suit their respective hardware. You must obtain the bios file from the mainboard manufacturer or the laptop manufacturer

Oh and bios files are free as are drivers etc from the manufacturer. Stay away from these scam sites trying to sell you files.

I'm afraid that Clevo no longer supports older laptops such as D470W.
I found this link for older Clevo notebook: https://repo.palkeo.com/clevo-mirror/D4x0E/.
The model I was looking for is D470W (I got the service manual that is suitable even for D480W) because the code of its motherboard is 71-M4000-D04, while my laptop (Hyundai P57V for which there is no longer service assistance and a company to contact) has this code: 71-M4000-D03. Actually, it's a kind of Clevo's clone.
Well, if you have a look at that website, the last row of the table provides 1.08 BIOS version. Instead, I currently have 1.05 version, looking at the POST screen during last week. Perhaps, I should try to flash that bios and see what happens. Otherwise, are there other web sources from which freely downloading the BIOS versions for the laptop models above mentioned?

 

[solarium]

Red lead to the Base and black lead to the Emitter (which is attached to circuit ground, which is also probably chassis ground). Be sure to first remove your short.

Select DC on your DVM first. Check the voltage from power up and then for at least a few minutes thereafter. This signal might be PWM'ed (not DC), in which case select AC on the DVM or use your digital probe and listen for a rapid buzz. This buzz would change tone if and when the fan is called on to increase/decrease speed.

The basic point here is to look for signs of meter deflection (or the presence of a PWM signal) from two possible varying signal types (DC or AC). This indicates that the appropriate controller signal is being applied to the controller transistor but it is not responding and, thus, is defective.

If there is NO apparent signal on the base of the controller transistor, then you've got a much bigger problem and you might consider just putting up with your current working solution (however annoying).

If I'm not wrong, the signal for temperature, coming from CPU, is converted in serial form by U27. Look at this picture taken from the service manual (**broken link removed**) on page 88 (Socket 478 & ITP):

I traced U27 on the motherboard. It should be an integrated circuit. I saw 8 pins each side, so 16 pins in total. But I'm afraid that a simple DMM isn't suitable for testing that component. Or can I do something? Someone told me that the origins of the problem can be traced in a fault of U30. I tried to find it on the motherboard but I couldn't (perhaps it's under the protective aluminium sheet that I avoided to remove). However, would you recommend some measurements for this component? Have a look at this picture from the same manual (page 109, LPC H8):

So, as you suggested, I connected the black probe to Q21 emitter (ground) and the red one to base and then collector. At the very beginning with motherboard on, at the base I measured 0 V (when even the other smaller fan wasn't active), then 0.18 V till 0.37 V (this when the other fan was at maximum speed and the main fan still didn't spin, even if moving in small jerks), finally it reached 1.24 V (while regurlarly spinning). Then when the main fan stopped I measured 0.37 V and I noticed that the voltage got back to 1.24 when the other fan began to spin faster. Perhaps, CPU sends signals to both fans but while the smaller fan increases the speed, the main one is only able to move in jerks, even if there is the same voltage as when it's spinning. With a screw driver when I heard the other smaller fan increasing its speed, I manually helped the main fan to go and I succeeded. But then, why only after the shutdown (and an excessive temperature) does it start spinning (and at full speed)? Does this mean that the fan is faulty?

Let's talk about the collector. At the very beginning with Mobo on, at the collector I measured 4.41 V, then when the other fan started spinning the voltage dropped to 0.81 V and when the other fan increased its speed I measured even less volts (from 0.58 to 0.64) and at that point I noticed that when the main fan showed signs of movement, the volts increased to 0.81 (for a fraction of second, i.e. for the duration of those signs). Finally, when regularly working it reached 0.60 V.
I even measured voltage immeditely after the shutdown: 0.93 V at the base and 0.24 V at the collector.
What does all this mean?
Now, other components to test?

Could I test FAN_SEN with my DMM? There are a diode and a resistor for FAN_SEN. Should I test them? If yes, what measurements should I take?

Anyway, I noticed that during the time of missed spinning (about 30 minutes), the fan moved in small jerks but without starting spinning as it should have had to. Only after the forced shutdown (caused by the excessive temperature), when I turn the Mobo on a few seconds later, the fan starts spinning (at full speed but for some seconds because then it sinks into oblivion again!), otherwise I've to manually let it go. Isn't it a kind of thermal problem? Isn't it a symptom of the so-called cold joints? Or is there a faulty SMD component (transistor or something else closer to processor, unable to trasmit the signal unless the temperature gets excessive)? Or, last, do these symptoms have the characteristics for asserting the corruption of the BIOS code? Or more simply a faulty fan?

 

[tunedwolf]

Here is a Clevo mirror site containing not only the latest Clevo bios, ver 1.09, but also a couple of earlier versions: https://repo.palkeo.com/clevo-mirror/D4x0E/

 

[cowboybob]

Let's talk about the collector. At the very beginning with Mobo on, at the collector I measured 4.41 V, then when the other fan started spinning the voltage dropped to 0.81 V and when the other fan increased its speed I measured even less volts (from 0.58 to 0.64) and at that point I noticed that when the main fan showed signs of movement, the volts increased to 0.81 (for a fraction of second, i.e. for the duration of those signs). Finally, when regularly working it reached 0.60 V.
I even measured voltage immeditely after the shutdown: 0.93 V at the base and 0.24 V at the collector.
What does all this mean?

These values would indicate that the controller transistor is working correctly and is, presumably, getting appropriate base biasing. By way of an explanation, a barely or non-conducting transistor (in the configuration shown in your posted schematic) will have higher voltage on the collector than a conducting one: as the base biasing increases the semi-conductor layer between the collector and the emitter transitions from being an insulator to that of a conductor, thus taking the collector closer to ground potential.

Do you access to another fan (with the appropriate connector)? If so, unplug the current fan and try the replacement so as to eliminate the current fan as an issue.

As for BIOS issues, a re-write is a bit radical. Have you investigated software options, such as this (https://lifehacker.com/5866009/cont...ance-when-you-need-it-silence-when-you-dont)?

 

[solarium]

Do you access to another fan (with the appropriate connector)? If so, unplug the current fan and try the replacement so as to eliminate the current fan as an issue.

No, I just have a couple of old PCs with bigger fans (12V). I even tried to ask for a small fan to small shops involved in reparing activities. The result is that they do have old motherboards with fans, old irremediably damaged laptops destined to be brought to a collection center (for waste disposal) but they don't want to sell any possible spare part that can be recycled. I saw with my eyes a big box full of motherboards with fans. Who knows how many of them would have been suitable for my purpose! They'll never use all that stuff. When I asked for an old fan, they began to shilly-shally... saying, we don't have the exact fan model you are looking for, just search on the internet... even if I told them that any could be suitable (voltage is always the same, only connectors may differ) because I'd have managed to adapt them inside my laptop. The truth is that they wanted me to let them replace the fan, recycling an old one that they did have. They wanted to be paid not for a ridicolous fan but for labor!

As for BIOS issues, a re-write is a bit radical. Have you investigated software options?

Yes, in particular speedfan but it cannot control any fan on my laptop, as the current BIOS revision (running on my laptop) doesn't provide this feature.
As my battery is gone, I'm very tempted to install a fan controller just in the battery compartment, removing the unuseful battery. I should install a temperature sensor to allow the automatic activation of the fans at a certain speed. Doing so, I'd bypass many electrical components in the motherboard that manage fan's operation. Would it be possible to do something like that?
But the space for placing a controller (inside battery compartment) is a bit smaller than the classic computer's drive bays. Perhaps, some fan controller models have smaller dimensions and it fits in such space.

Anyway, I got some news for my problem.
Last days I found out that there is an old BIOS revision that supports fan control, I think it's the last revision released. I didn't know that!
Now, I think it's worth trying an update. Main difficult: keeping system on during the update. As the transistor is hardly accessible with laptop completely assembled, I should find a way to have the fan working all the time (at least until the end of the update). If I want to short transistor's pin, I need to keep the motherboard in vertical position and without the bottom case, as the transistor is located on the bottom of the motherboard. Otherwise, I couldn't reach it with a screw driver.
Instead, I can get much easier access to the connector of the fan which is on motherboard top. Lifting the keyboard is enough to reach that connector. Is there a way to do something on the connector? Perhaps something on the tachimetric pin (corresponding to the yellow wire)... is there any trick to do?
Or could I easily opt for externally powering the fan? But then the fan should be disconnected from the motherboard. Will the processor react badly impeding even the start up?

 

[KeepItSimpleStupid]

How about an external house fan or other fan while the update process is occuring?