Hello mister @Magenta
And good day. I wake up at 1 pm. I stay late last night.
By the way, i dont understand how you are measuring diodes with an ohmmeter but on my multimeter set on 200 ohm, I got 1 (in air) value on ALL diodes. I check it from curiosity. Then I check the normal way, I switched to diode measuring setting and I got the normal reading for measuring diodes. Also interesting fact is that all those germanium diodes (transparent glass red marked ) are all measuring (on diode setting) 700-800. But the 2 black diodes on the bottom, are reading 138 and 270. What are these readings anyway? I knew it some time ago, but i forget it now. I think is miliV? like the forward voltage?, I dont remember clearly now.
And yes, I checked and double check both ways of each diode. All are ok. I especially double check because of the lacquer isolation they have on the board and that is misleading the reading. So I had that in mind all the time.
I did more than testing those diodes you put me to check.
Im also providing you with the ENTIRE circuit that I back-engineer it myself alone.
This should answer all your questions. I used the continuity function on my DMM and follow and find each track this way. Those little round dots are called "vias" a term from prototyping electronic boards. It means a hole that connects between layers of tracks on the same board. A sandwich of layers of tracks basically.
The 3 big black circles are the pins of the coils.
I know is poor resolution but my phone is shit. We have to deal with what we have.
If you cant understand something from my drawing, ask and shall I answer (like you english like to say).
This drawing is also very useful if we compare it to the original circuit from the datasheet. So please, if you find that circuit, or !similar!, it would help immensely to this cause. I can pretty draw it in PS, but.. is a pain in my buut so we will use this as it is for now. If is absolutely necessary, I will PShop it. But right now i dont see its the case.
I didnt read the datasheet (as always) haha. I had to concentrate on other things. But I give my best to what I already presented here. So... I hope is good enough.
This drawing i made is exactly how I see the electronic components arranged on the original board.

 

Sadly, your fan is very probably toast from having its power misapplied.
Reverse polarity protection costs money. When the fan is used in a product, there is little need for polarity protection, so they don't add it to the design.

Study this fan carefully to sort out it's connections, then test a fresh one that you have not already killed.

 

Sadly, your fan is very probably toast from having its power misapplied.

Well, everybody here is thinking the same, me included. But let's poke the dead 'shit' more and HopeFully find the damaged component, somehow. I know I ask a lot, but lets do it anyway. Im suspecting one of the IC's or even both. As you can see, there are 2 tracks starting direcly from the wire pads into the IC pins (through those 0 R jumpers, on the bottom left, under the IC1).
Im also inclined, as a very last alternative, to drive the coils directly ! Like the old stepper motors were driven in 2001-ish. Though this thing is having 3 coil pins and where the 4'th pin should be, is a X formed by the copper wire, uniting the 2 coils. Very weird assemble !

 

I will work with you a little longer but need time to study your sketched wiring diagram.

 

Mister @Magenta, dont feel rushed ! Take all the time you need, really.
This is a hard subject and I am doing this diagnose in parallel with other little "fun" projects.
- This cover is what I'm working from last night and today. Right now I have my fingers dusted from the wood dust I cut. Remember that power source I show it in the videos, when I powered the BD139 motor driver? I could easily poke my fingers inside it, where 220V was open to touch, or even more that 220V, on some capacitors. So I was a bit brown in my pants, working that way. I prefer the safer way! It was in plan for a VERY long time to make a case for that power supply, but i never had the energy for it, or inclination. But now, when I successfully put it to work, WHEN I NEEDED IT (that's very important), to power those 8 transistors and their leds to drive the motor, and it did it's job perfectly fine! it gained my trust and respect again and realocate its importance in my book, and I decided to deal with it. SO here is the result so far: VERY freshly finished:

It even opens the case from a hinge ! (im thinking to add a second hinge, though I am not opening it that often).

I used Poxipol to glue the lateral sides. I trust poxipol!!! But on these dimensions...i hope it will not crap on me. We we'll see in time. But for now, it looks awesome ! Strong built, exactly how i like it. Ha-ha.

Again this is a little side project. But im keeping an eye on this motor issue in the same time. And reading everything you say here.
Again, this motor will be used for a heating gun. I already succesfully enough converted a normal PC fan into a modest blower, that actually blow a good quantity of air through its nozzle so far. This motor-turbine we are dealing here, should overpass the air-flow of my modest conversion with the fan. Thats why I am insisting on it !!!
But I have alternatives, is what Im saying.
This heating gun, is a very simple concept, but oh boy, it is so hard to actually build it.
But it's "fun" project, and very usefull, if I manage to make it work in the end.
Wait until I will add the electronic part..uhuu, thats the real fun then.... just putting ideas in perspective. Haha.
You are doing great progress, so continue, and come with some results or directions for me to do.

 

Well, if people are working so hard these days, I thought to make a Clean back-engineered circuit in PS.
I've added all the annotations and values that we discovered so far.
Updated circuit v2

 

Re #47. I think this drawing is close but not exactly the same as the circuit on the board. I have attached a copy of your drawing with some red lines and crosses to indicate how I think it is actually wired.

Pins 1 and 3 of the SP8K4 must connect to Gnd/0V. This will help confirm the Gnd lead is the Black one.

Pin 3 of the FAN ic is the tacho output so if you follow it you can confirm which lead is the tacho output. The grey lead.

I reckon the Vin lead (brown) is the lead which connects to the Pin 1 of the FAN ic via a diode (D1 or D2) and the Vcc(Grey/Black) lead goes to the common terminal (which I circled in my attachment) of the two motor coils via a diode (D1 or D2) .

The red diodes are protection diodes to safeguard the power transistors in the SP8K4 chip.

The four legged black chip is indeed the Hall sensor.

Transistor T1 has its emitter connected to 0V and base to pin 5 of the FAN ic and its collector to the gates of the SP8 power transistors through '101' resistors; when the FAN ic detects a stalled motor the voltage on pin 5 rises, turning on T1 thereby grounding the gates of the power transistors in the SP8 removing current to the coils.

I suspect the board has a 3 wire power supply: Common Ground (marked GND) 0V, +V1 (marked Vin) to FAN ic circuitry and +V2 (marked Vcc) to SP8 motor circuitry.

Of course could be wrong but I think we are getting closer to being able to do some diagnostics.

Probably enough for now. Once you have been through these items we can confirm which are the power leads and supply 12V to the board. We will then take some voltage measurements.

 

I am glad you produced an enclosure for your power supply. You might want to monitor the internal temperature with a thermometer and if there are signs of overheating include some ventilation holes and a cooling fan (if there are none already).

 

I am glad you produced an enclosure for your power supply. You might want to monitor the internal temperature with a thermometer and if there are signs of overheating include some ventilation holes and a cooling fan (if there are none already).

Oh, thank you ! It has already plenty of long gaps in it. I didnt build it with being hermetic in mind. I deliberately leave some large gaps between some panels. It has air flow already. Im happy you are aware of that as well !!!! VERY good for you! Seriously. Your idea to measure how hot it gets is not bad at all. I didnt think to actually measure it, to be sincere. I am way too trusty guy. haha. Usually I smell hot metals or components or wood. You know, the faintest smell. I have a dog nose and i use it perfectly in electronics.
- And to prove that I know exactly what you are talking about holes, here are some pictures I took VERY long time ago, years ago, when I made my OWN holes in already crumbled and very bad designed cases that gathered a ton of hotness inside them and I notice that, and i did "at least" these holes to them. Of course I had to open the case, make the holes and assemble again. The white monitor was very hard to take out its back plate, not to brake the fragile plastic little clamps. But i did it and is fine even as we speak. As a "fun" real fact, I showed these little cases with holes I made, into a romanian electronics group on facebook, when I didnt know much about them, and they ALL literally lough of me, being so dramatic or precaucious (and even stupid), and also "worried" that I may damage the entire device, and when I ask them why it would damage it, they respond that "those who design it, know it better". Reaaaaallyyyyy? Hahahaha. This is my lough right now. Of course I didnt stay long between them, though I spotted 1 or 2 other serious guys like me, but I didnt want to risk it, so I leave them be. Fun, right? Haha.

Yes, if this power source will get [too] hot, I will add a series of ventilation holes to the lead, or lateral panels. I will keep it in mind. What I have there, is actually the power source from that Macintosh computer (monitor+PC all in 1 case) IMac or something was called, that I receive it from an old friend, who buy it already damaged in the hope of repairing it, and he also burn something in it as well, damaging it further. I took it for the components. And I realized its power source is intact. So I use it. But those turbine motors, I never seen them work, or at least I dont remember them working in any way. They may be already burned or damaged when I receive it. Thats what I am thinking. And I didnt "test" them that much to burn them. Not until recently when I build that BD139 transistor driver with arduino. I admit, I got crazy when I commanded it through arduino. I kind of used every wire on them on 12V. I didnt smell anything, i didnt hear or see anything. Dead all the time !!!! And by looking on their skematics, Im not sure I could possibly damage with only 12V, ANY of its wires I/O's. What I highly suspect may had damaged them, (I have 3 of them) must probably be a Spike , or plural, Spikes. But that might happen before I received them. Its my #1 suspicion. But I am very curious to find the actual damaged component!!! Thats why all this operation on them. Ill have to measure them thoroughly, powering the motor on brown and black wire, and check the current where it goes and where it stops. That is my plan how to debug it. I dont really know much about debugging it, it is what I can think of, the best thing to do in this case. Hmmm. I also suspect is dead like a rat. But if its a resistor or some sort of fuse somewhere, easily replaceable? Thats what Im hoping for.
In the same time, Im trying my best on attaching the heating element to the blower I made. I powered today the heating element and its nichrome wire is getting white hot from my 110V (220V with a power diode on 1 wire), and also it is elongating, like draining down, due to gravity, reshaping like an long oval, like an old lady boob. I really dont like this effect. I attached a poxiline extention and put some distance wires , to not permit the nichrome wire to touch the surounding metal case. But the poxiline, got in flames, or parts of it got black burned. Nothing serious, I blow on its flame and got out very quickly, but the sad thing is that it rupture itself from where it was attached. OOOOH, Im so dissapointed now. As I said, extremly hard to implement, this very easy concept. Eh.... I'll have to find another sollution to keep that heating element straight and not touching the metal cover around it.
Thank you for reading so far. Haha.

 

If you could check my diagram with red lines and crosses on matches your circuit board I will then detail some voltage measurements to make which may lead us to the defects on the board. For example I reckon the left end of D1 goes to pin 1 on the FAN ic and the left end of D2 goes to the bottom left common terminal l circled in red. The right end of D1 goes to Vin and the right end of D2 to Vcc. I suspect D1 and D2 may be defective but need to power up and take some voltage readings to confirm.

 

Here I made the testing again, live, for you to see that my drawing is exact as I measured in reality. Nothing is from imagination, though I understand if you dont believe an artist for having too much of it. Haha
Please check this video made specifically for you mister @Magenta

And thank you very much for your commitment, as always.
I start to believe, without too much testing, that is truly dead as a rat. This is it then. My only hope now is to try to drive those coils directly.
- It is possible to drive those coils directly? Without any component on its board?

 

_q12x_ Once again a trademark clear video. To be clear myself - I mean no insult to you when I question your drawing it is just I find it hard to comprehend the circuit would ever work - so the state of the board you have discovered using the continuity function of your meter may well be the problem. I caution though that electronic continuity measurement function may give a beep even when the resistance between the probes is not a short circuit but some low non-zero Ohms. For example, your drawing shows a direct connection between gnd and Vcc - very odd indeed. You could check this is the case by connecting the probes across a 1kOhms potentiometer and moving the slider.

I will check again the FAN datasheet to see if there are different types with there own pinouts.

I will draw out what I think the circuit should be from studying the datasheets for the two ics and for the fan itself. You know me - I like a puzzle to solve as much as you like a project to succeed with!

PS: On your other project have you considered an 'instant soldering iron' using some sort of tweezer arrangement which applies a large but low voltage current to the solder joint to produce rapid Joule/Ohmic heating?

 

https://pdf1.alldatasheet.com/datasheet-pdf/view/118389/FAIRCHILD/FAN8413MX.html

I have been using as my reference the circuits on pages 6 to 9. Looking at page 7 for example you will see the Hall sensor is normally between two resistors of equal value (R1 and R3) and then across the supply to the FAN ic - this is not what you have discovered with your meter. The coil driver power transistors Q1 and Q2 page ( which are in the SK8 ic of your board) are fed separately via the same value resistor from pins 7 and 8. The power transistors in the SK8 are n channel enhancement mode ones so to turn on need to have their gates biased towards the positive rail. Pin 5 provides a voltage which ramps up and down unless the motor stalls when the voltage ramps up only to a higher voltage which turns on the npn transistor on the board and thereby removes the bias voltage to the coil power transistors until such time the fan is not stalled. To remove the bias from both power transistors of SK8 the collector must be connected to their gates via their own resistor.

The electronic commutation of the motor coils demands symmetry of circuitry between that which drives one coil and that which drives the quadrature coil - which your drawing does not have completely. I hope this helps you understand my thinking and puzzle.

A simple test to help me. Please connect GND to 0V of your 12 V psu.. Connect Vcc and Vin to +12V. Now measure these voltages:

1. Across D1
2. Across D2
3. Between pins 1 and 5 of FAN ic
4. Between pins 5 and 6 of FAN ic.
5. Between pin 8 and pin 5 and then between pins 7 and 5 of FAN ic.
6. Between collector and emitter of the npn transistor.
7. Between pin 8 and pin 1 and between 6 and pin 3 of SP8 ic.
8. Between base of npn transistor and pin 5.
9. Between pins 1 and 2 and between then 3 and 4 of SP8.
10. Between Vcc and pin 5 of FAN ic.
11. Between Vcc and pin 1 and then pin 3 of SP8 ic.
12. Between Vcc and Vin.
13. Between Vcc and pin 5 of FAN ic.

 

Trademark video , lool. Thank you !

PS: On your other project have you considered an 'instant soldering iron' using some sort of tweezer arrangement which applies a large but low voltage current to the solder joint to produce rapid Joule/Ohmic heating?

I have no idea what you are referring to ! For certain, I don't know all the tools in this world so please show me something extravagant.
I started your list for tests but... it failed in the beginning, unfortunately. I had the inspiration not to test it before filming. All the experience was first time.

Also, we will stop this endeavor !!! I thank you for the effort. But there are other more pressing issues that must be resolved.
All we did here was to try it. It didnt work. At least I know im not stupid, by trying it alone and not working.
I am keeping my eyes on the prise, meaning, the heat gun. So, it is almost working and almost done. I will actually try today to test its power on the solder. But I need to make a new dimmer circuit with a triac and diac, like the one I presented in my latest movie. Not to keep it at maximum as it is now.

 

Instant heat soldering iron.

 

Really? that's how its called? I was calling him simply "soldering gun" because it is looking like a gun and is soldering. I have one of these, with a big and very well made transformer, from communism era (70-80's). It is working even today, but I stopped using it. Because it is destroying any field effect components - transistors or IC's. I know because I use it and experienced it on exactly a field effect transistor, and I see him destroyed (not working anymore in its circuit). From then, I said "ahaa", and I used only the soldering iron from my blue station, specifically to avoid this field effect destruction from using my tool. And it is point to point desoldering tool, don't forget. While what I want to make, the heating gun, is a large area desoldering tool. Very beneficial especially for a multi legged component like an IC or those IC that are facing with their tabs instead of legs, on the board. Those can only be taken out with a heat gun like this. I will use it for general smd's components and easy to take out multiple components at once, at least that is my intention. And avoid point to point desoldering because it will take me forever. I hope you understand better now, my intention and my projekt.
Your circuit for a soldering gun is valuable in it's own right. I give you that. But not for the moment. I will probably come back to it, sometime in the future, and make it by curiosity alone. It is a fascinating circuit, that replace the heavy transformer. Very interesting indeed. I will pass it for now and follow my projeckt that i am almost completing it.
Thank you for your contribution for now ! You did good. Currently I am updating and pushing on this projeckt: https://forum.allaboutcircuits.com/threads/how-to-make-a-heat-gun.178797/?cb=1622238742

 

You guys have been funny to watch during this mess. While the origin of this fan may have been from an Apple product, it isn't a real Apple device. It is a common 4 wire PWM fan that normally gets it's drive information from the computer motherboard. there are many hits if you just would have used the terms "4 wire computer fan" . One of the top hits that could have been used to drive this before it was probably destroyed by what was done to it. https://www.electroschematics.com/4-wire-pc-fan/

 

'been funny to watch'. I know no slight was intended and none has been taken, but it allows me to write the next paragraph.

What do I admire about _q12x_ ? This fellow is an intrepid experimenter, determined discoverer, experiential learner, does not give up until the winning line has been crossed, someone to build a boat with if marooned on a remote island, open and honest. An ingenious individual. I take my hat off to him. To me he is a true engineer. I wish he worked for me before I retired.

 

'been funny to watch'. I know no slight was intended and none has been taken, but it allows me to write the next paragraph.

What do I admire about _q12x_ ? This fellow is an intrepid experimenter, determined discoverer, experiential learner, does not give up until the winning line has been crossed, someone to build a boat with if marooned on a remote island, open and honest. An ingenious individual. I take my hat off to him. To me he is a true engineer. I wish he worked for me before I retired.

VERY TRUE ! I totally agree with you mister @Magenta and all you just said here and I admire the fact that you see it as well. Very, very good ! And thank you. And as me, I can see in you some creative force, that will to help and to give all you got. That is very good. But the projeckt is not done yet and I invite you to participate longer until, hopefully, I will make it better than a pile of failures. It must work once !!!! Thats all it must do. Whithout taking fire - hahaha.

 

The last idea: