Powersupply washingmachine. Relay problem?

[Moreno83]

Hey guys ,

I got a Samsung washing machine that wont start the motor. Im 100% sure it is the mainboard because i tested it with a working board.

Mainboard is DC41-00189a

I reflowed all the connections but it simply wont start. It turns on and injects water into the machine and also drains the water but it wont run the motor. It keeps trying to start the program , i hear a click...after click after click.
So because of the clicks ( relay ) i measured both relays in OHM and i got the following results .

Working board both relays measure 160ohm
Defective board one relay measures 160ohm , other one 154hom.

Now to be honest , i dont know 100% sure how to measure a relay. Just looking at the board it has 4 connections with 2 going to ground? I measured between 2 legs that has actual traces on the board because it is a kind of switch.
How do i know for sure that this relay is dead? I measured in circuit.
I followed the traces of the "bad" relay and the resistors are all measuring ok.

The relay is a SFK-112DM


Hope someone can help me!

[R_J]

Re: Powersupply washingmachine. Relay problem?

If the relay clicks, it's likely the coil is ok but I suspect the relay contacts are burnt (open)
If you remove the relay you can apply 12 volts (9v battery should work) to the coil and put your ohm meter across the relay contacts

[CapLeaker]

Re: Powersupply washingmachine. Relay problem?

you have to take the relay out, power the coil, and check the other side with your Ohm meter. What's written on the relay in question?

Next question is: Does the relay get power in order to engage? If it doesn't it won't switch on either.

[Moreno83]

Re: Powersupply washingmachine. Relay problem?

Thanks for the quick replies!

Im not sure if THIS relay clicks , need to figure that out tomorrow. Will also take some pictures of the back of the mainboard.

Below is the relay. Both are the same.

https://ae01.alicdn.com/kf/HTB1TKAUS...pg_640x640.jpg

[Moreno83]

Re: Powersupply washingmachine. Relay problem?

you have to take the relay out, power the coil, and check the other side with your Ohm meter. What's written on the relay in question?

Next question is: Does the relay get power in order to engage? If it doesn't it won't switch on either.

I dont know but the 154ohm does not look good to me compared to the other relays on the working board.

[Moreno83]

Re: Powersupply washingmachine. Relay problem?

If the relay clicks, it's likely the coil is ok but I suspect the relay contacts are burnt (open)
If you remove the relay you can apply 12 volts (9v battery should work) to the coil and put your ohm meter across the relay contacts

So i checked the datasheet. It says i need to measure 160ohm for 12V but i measure 154ohm.
Will remove the relay and replace it with a working one to see what it does.

[sam_sam_sam]

Re: Powersupply washingmachine. Relay problem?

So i checked the datasheet. It says i need to measure 160ohm for 12V but i measure 154ohm

154 ohms is ok resistance for that relay

These type of relays (sometimes real crap) my guess is that the contacts are either completely gone or are bent out of the where they should

One thing I would check is if you are getting power to the relay or not

Can you please tell what part is under that large heat sink

If it has bunch pins on both sides of a large ic chip then more than likely it is some type of IGTB module if has one that might explain why your motor might not be running

[budm]

Re: Powersupply washingmachine. Relay problem?

I doubt that the 154 Ohms DCR of the relay coli is the problem.
If you do hear that relay click on then you should check the Voltage between the relay contacts to see if it shows big Voltage drops or not, if the contacts are closed and they are OK then you should barely see the Vdrops on the relay contacts when the contacts are closed.

[Moreno83]

Re: Powersupply washingmachine. Relay problem?

Thanks for the replies.

So i need to measure the voltage on the 2 contact on top of the relay right?
I dont know what is under the heatsink but it could be a IGBT. Problem is the sillicone , every part is glued in and heat cant escape.

Normally reflowing the contacts fixes the problem but it wont even calibrate the machine.

[Moreno83]

Re: Powersupply washingmachine. Relay problem?

So i rechecked all the soldering under a microscope and they are now all fine ( they were bad ).

The original problem was a 3E error which means the motor cant run. After resoldering the pads the error disappeared and the machine closes the door , inserts water and then the relay keeps clicking. On the display i can see the program keeps restarting itself and the relay clicks.

Do i need to lift the cables a little and measure the voltage on topside of the relay or bottom side?

[sam_sam_sam]

Re: Powersupply washingmachine. Relay problem?

I dont know what is under the heatsink but it could be a IGBT. Problem is the sillicone , every part is glued in and heat cant escape

If you see this under the heat sink I have seen this before and more than likely it some type of IGBT module

Here is something you could try unplug a sensor and see if you can force it in another error

There are some controller that depending on how high the error is it will not let the machine rest until you force it another error

I have a machine at work that did this when the Servo Main Power Supply error out it keep showing the error for auxiliary voltage/current monitor—-> but It really was the Main Servo Voltage/Current monitor but error does not show until I forced it into another error by unplug the enable command line plug so it would not get the enable signal which force it into another error plug enable plug back in then it gave me the real error code to what was the real problem with it


Or see if this controller has a way to do a hard reboot or a way to reset the controller

Can you measure the power supply voltage on the board where the switching power supply regulator is to see if it steady or not

I once had a switching power supply that keep restarting and it was switching power supply regulator chip that was bad but I first recap that portion of the board frist that is how found the problem with it

[Moreno83]

Re: Powersupply washingmachine. Relay problem?

How do i do that? Remove the plugs from the relays and turn it on? Ps the sillicone is on bottom of the board and on top. ( Look at the picture ).

[sam_sam_sam]

Re: Powersupply washingmachine. Relay problem?

How many wires are on the motor that will not run and is there a data plate on this motor

[Moreno83]

Re: Powersupply washingmachine. Relay problem?

The motor is not the problem because i got a working board and with that board the machine works perfectly.
Its definitely something on the board.

This is the backside of the board with bottom right and top right the relays. Look at the solder and how bad it is!

https://tweakers.net/ext/f/pM1cYoGVz...nBAOE/full.jpg

[sam_sam_sam]

Re: Powersupply washingmachine. Relay problem?

What is the part number of the chip that is marked on the photo

Yes a lot of soldering joints look like crap in that picture but is it because of the way the light is hitting the board

Would it be possible to take a video clip when it keep restarting and show the display while it clicking the relay

[R_J]

Re: Powersupply washingmachine. Relay problem?

It could be that the ipm is bad and not the relay, the ipm is used to drive the 3p motor.
There is a small black fuse (f2) between the one relay and the blue poly cap, is it ok?
If you can check the voltage across the bridge rectifier and make sure there is dc voltage there to supply the ipm

[Andrew F. Ali]

Re: Powersupply washingmachine. Relay problem?

The relay oil is not getting the signal power to turn it ON fro the contacts to close. The has to be removed from the circuit and powered wit a 12Vdc supply. When it 'clicks' the top pins should close and that is measured for continuity. If that work then trace the signal back to the source. Most likely there is an 'open' on the copper trace to the relay coil. Don't forget to check the diode across the coil. That could be short cct.

[R_J]

Re: Powersupply washingmachine. Relay problem?

They use a 3 phase a/c motor, the relay's don't control the motor, Also there are 5 different relays on this board

[Moreno83]

Re: Powersupply washingmachine. Relay problem?

What RJ says is true. 5 relays on board. 2 big ones and 3 small ones.

The only relay that clicks is one of the small ones , i think its the one on the left. The big relay close to the small ones is not clicking.

I will measure the fuse , didnt see that fuse!

I will remove the big relais from the board but i dont have a dc powersupply today , will be tomorrow!

[R_J]

Re: Powersupply washingmachine. Relay problem?

I suspect the relays are used to control other functions Not the motor. It is a 3 phase motor.