This board comes from a ventilator motor in a ventilation system.

The motor is not shown, only the PCB in the motor housing. The ventilator is controlled by the main ventilator system board with a PWM signal.

And that is about all I know. I never worked with SMD component and haven't done a lot of repairs by measuring.

So I have just started out looking for burned out components in which came out negative.

I have now started testing what I know as a diode. its the component marked with a red circle (IMG_4188).
It measures 0.373 v one way and 0.379 the other way. If it is a diode shouldn't it measure zero one way? Or is it even a diode?

I posted a photo of each side of the PCB.

 

hi,
first of all, are you sure the PWM signal is OK ?

As about the PCB, check the white fuse 3.15A, the big red resistor ( 68 Ohm?), and three resistors 33R0, all close to the big brown electrolytic capacitor. These three resistors do not look good

 

Thank you for your time.
Fuse is OK
big red resistor is OK
the 3 33R0 is okay. They do look dark but it is because theres som kind of stamp on the board and resistors.

I am sure the PWM is good because a new ventilator works fine.

So the diode I mentioned is nothing?

the big brown capacitor, I measured to 44 uF. Is that good?

 

I'm not sure about the diode checked in circuit. Let's say, 90% it's OK. These small diodes rarely fail.
44 uF is OK for the 47uF capacitor.

I remember i tried to repair a similar ventilator/fan , it was an expensive Ebm Papst (?) ventilator. The big chip with thick pins was faulty, or the small chip tied to it, i do not remember which one. The big one is a frequency converter output stage.

There's 3 wires from the motor winding, check the resistance of the winding

 

I have the rest of the ventilator at my work place so i will check the winding tuesday. I can also take a photo of the motor.
Is there a way to check the chips?

 

Check the aluminum capacitor in SMD style. These in SMD are not very reliable.

It's not easy to check the big chips. Take the datasheet , energize the PCB and check the voltages on the pins.
That's probably the most you can do

 

aluminum cap measures 60 uF

Resistance between any of the 3 pins on the motor measures 166-169 ohm.

 

Sounds like winding is OK.
Check the SMD capacitors around the big chip with thick pins for short.
If no result, power up the PCB. Use a DVM in DC volt mode , check the voltage across pins of the big brown capacitor. Should read 300-350VDC. Be carefull with high voltage

 

SMD capacitors around the big chip don't seem shortened.

But the highlighted component (not sure what it is) in the picture is. Should it be?

 

SMD capacitors around the big chip don't seem shortened.

But the highlighted component (not sure what it is) in the picture is. Should it be?
View attachment 319251

It's 4R7 resistor. 4.7 Ohm

 

The 4R7 is fine too.

I will try to power it up later in the week.

 

I advise you to find and study the data sheet of the big chip. Will need to measure voltages on the pins

 

I found the datasheet here
http://www.elektronikjk.com/elementy_czynne/IC/FSB50250US.pdf

I dont have much experience with reading datasheets other than finding the right pins when to use them.

 

Datasheet, Figure 8. Example of Application Circuit .

Your circuit may differ slightly from #8, but will be similar. So, Ground is Brown capacitor Negative pole. Measure voltage on the pin #17, should read about 320VDC. Measure voltages on the pins #2,7,12 , should read about 14VDC.
In normal state, when fan is running, the chip is driven by pulses on inputs #4,5 , #9,10 ,#14,15.

When running, the Hall sensor sends several pulses on every turn.
Be careful when measuring so that the probe does not slip and do not short the pins

 

I have replaced the big chip. While checking for shorts I found continuity between pin 20 and 21. Ive looked under microscope and I do not see anything short at all.

Is there suppose to be continuity between them? I measured the old chip and that one hasn't.

 

Pins 20 and 21. Power mosfet transistor is tied to the pins. Continuity does not indicate , that it is really a malfunction.
Basically, you have undertaken complex repairs . The fan is made according to a complex scheme , with microprocessor control .

 

thanks I'll reassemble the ventilator and put it in a ventilation system next time I one that mailfunction.
Thanks for all your help. I appreciate it.

 

Circuit diagram would be very helpful.
Unfortunately, I don't know where to get it