@LesJones
You with me buddy?

 

What was the result of the test. Fault finding works by working out a possible cause for the problem then doing some tests to prove or disprove the theory.

Les.

 

What was the result of the test. Fault finding works by working out a possible cause for the problem then doing some tests to prove or disprove the theory.

Les.

I didnt do it. Waiting for you to confirm if i got it. Don't wanna cause more damage.

 

Hi elli,
I have just been looking at the schematic again and realised that the point it told you to connect the negative lead of you meter to was the wrong ground. I have found a way that is easier to test the 12 volt DC supply. If you can get your meter probes into the back (Wire side.) of the plug that plugs into connector CN4 (12 pin black connector at the top right hand corner of the picture of the board.) If you test between pin 2 (Negative) and pin 12 (Positive) you sould get a reading of 12 volts DC. I can't read the pin numbers (If there are any.) on the picture so you will have to see if you can read them. I have also found that you can get to the bottom end of the main relay coli on pin 6 of connector CN13. I had been interpreting the label on this pin (IC6_12) as pin 12 on integrated circuit IC12 which I could not find on the schematic. So now you have the information to see in the coil on the main relay is being energised. Yo can do this by measuring the voltage between CN14 pin 12 (+) and CN13 pin 6 (-)

Les.

 

Hi elli,
I have just been looking at the schematic again and realised that the point it told you to connect the negative lead of you meter to was the wrong ground. I have found a way that is easier to test the 12 volt DC supply. If you can get your meter probes into the back (Wire side.) of the plug that plugs into connector CN4 (12 pin black connector at the top right hand corner of the picture of the board.) If you test between pin 2 (Negative) and pin 12 (Positive) you sould get a reading of 12 volts DC. I can't read the pin numbers (If there are any.) on the picture so you will have to see if you can read them. I have also found that you can get to the bottom end of the main relay coli on pin 6 of connector CN13. I had been interpreting the label on this pin (IC6_12) as pin 12 on integrated circuit IC12 which I could not find on the schematic. So now you have the information to see in the coil on the main relay is being energised. Yo can do this by measuring the voltage between CN14 pin 12 (+) and CN13 pin 6 (-)

Les.

Not really a connector, but rather...

\
Now what?

 

If you can't test for the 12 volt DC supply at the points where the flat cables are soldered to the board than try with you positive meter probe on D19 + and your negative meter probe on the end of R36 which is NOT connected to R35.

Les.

 

If you can't test for the 12 volt DC supply at the points where the flat cables are soldered to the board...

I think i can, but i need to know if my plan is feasible...which is to poke a needle through the protective silicone putty to the points, and then probe the needles with the multimeter. Would that work? I'm thinking of needles instead of the multimeter probes because the probes are too fat. Whatcha think?

...than try with you positive meter probe on D19 + and your negative meter probe on the end of R36 which is NOT connected to R35.

Not sure i understand what you mean by "...which is NOT connected to R35". The R36 you're talking about is the one circled in green in the image below, correct? And then the R35 yellow and D19 blue. Can you expand on this a little bit?

 

Needles should work providing that you have the capability to manufacture test probes with needle tips. (I have done this in the past to make contact with the conductors in alarm wiring by pushing the needle through the insulation.) I would just scrape some of the coating off the component wires using a smal craft knife or scalpal. If you look at the schematic you will see that one end of R36 is connected to the ground that you want and the other end is connected to on end of R35. You can identify which end of R36 is connected to R35 with a continuity test. (REMOVE THE POWER TO THE MACHINE TO DO THIS) This is the end of the resistor that you don't want as you are trying to connect your negative meter probe to the ground point that the other end of R36 is connected to.
I think the chance of you tracing the fault is very small as each simple test is taking so many posts to get you to do it.

Les.

 

I know it was mentioned that back side of the pcb is not accessible....
Why not?

 

Just did it... Positive probe on D19 + and negative probe on R36 ground, multimeter set to DC 20.
I'm showing no voltage. The multimeter keeps going between 0.01 to 0.00.

Appreciate your patience Les.

 

Now that we know that we do not have 12 volts DC output from the switched mode power supply we will see if we have any input to it. Measure the voltage between D22 negative end (With negative meter probe.) and D20 positive end. (With positive meter probe.) BE VERY CARFUL AS I EXPECT THERE TO BE ABOUT 325 VOLTS DC BETWEEN THESE TWO POINTS.

Les.

 

Now that we know that we do not have 12 volts DC output from the switched mode power supply we will see if we have any input to it. Measure the voltage between D22 negative end (With negative meter probe.) and D20 positive end. (With positive meter probe.) BE VERY CARFUL AS I EXPECT THERE TO BE ABOUT 325 VOLTS DC BETWEEN THESE TWO POINTS.

Les.

Done! 0.00 volts.

 

In the next test you are testing for about 230 volts AC (Set your meter to a suitable AC voltage range.) On the blue connector that plugs onto the connectors on the main relay there are two wires. One goes to the door switch. The other goes to the noise filter. Connect one meter probe to the this point. (It does not matter which meter probe.) Connect the other meter probe to CN4 on the board. It should read about 230 volts AC. In the schematic in post #21 it shows a 20 amp fuse in the wire from the noise filter. If this fuse is fitted to your machine it is worth checking it if you have not already done so.

Les.

 

In the next test you are testing for about 230 volts AC (Set your meter to a suitable AC voltage range.) On the blue connector that plugs onto the connectors on the main relay there are two wires. One goes to the door switch. The other goes to the noise filter. Connect one meter probe to the this point. (It does not matter which meter probe.) Connect the other meter probe to CN4 on the board. It should read about 230 volts AC. In the schematic in post #21 it shows a 20 amp fuse in the wire from the noise filter. If this fuse is fitted to your machine it is worth checking it if you have not already done so.

Les.

I don't see a blue connector that goes to a relay. I see a black one and a white one, like indicated in the picture below.

I am guessing this is the connector you're talking about. It says blue in the diagram but it's actually white on my machine.

Another thing is that it's the black wire that connects to the noise filter which has the fuse, not the blue one like the schematic shows.
And the only black wire (of the same thickness) which connects to the pcb is connected to the heater relay, which, looking at the diagram, indicates that it's the heater relay that is actually fused and not the main-relay.
I also tested the fuse...it checks out.

So, is it the white connector in the picture above that i should probe? If so then i would be testing "main relay #4" (on the picture above) against "CN4"'s wire...correct?

 

You are correct in that the connector labelled blue on the schematic is the white connector on your machine and the one labelled white on the schematic is black on your machine. We are not trying to test any relays at this point as they can not work without the 12 volts DC to drive the coils on them. We have proved that we do not have the 12 volt DC supply so we are now working back toward the mains input. In the first step back toward the mains input we found that we did not have the 300 volts DC input to the switched mode power supply so we are now trying to test is the mains supply is getting to the board. I had made a mistake In my last post (#53) I had followed a wire to the wrong connector. I should have said the white connector. (Which is black on your machine.) So to clarify We are testing the voltage between connector CN4 on the board and the wire to the black plug on your machine (Which comes from the noise filter ) . Did you check the fuse and was it OK ?

Les.

 

Yes i tested the fuse and it was ok.

Just to confirm...I should now check voltage between connector point #1 (the one where the black wire goes) at the heater relay, circled below...with CN4, correct?

 

The wire is shown as black in the schematic in post #21 If the other end of that wire connects to the noise filter then that is correct.

Les.

 

Done! I'm getting 217 volts...slowly climbs up to 220 volts.

 

The 220 volt reading is probably OK. It should be exactly the same as your mains voltage. The drift from 217 to 220 could be your mains voltage varying. You could confirm that you get the same reading directly on the output of the noise filter. ( Or WITH THE MACHINE UNPLUGGED FROM THE MAINS You could also measure the resistance from the two points where you measured the voltage to the output connections on the noise filter. You should get a very low resistance reading. (Probably less than 1 ohm.)) As you seem to have the required mains input to the board the fault is most likly to be The inductor L1, PTC1 (A thermistor or fuasible resistor.) or one or more of the 4 diodes D20, D21, D22 or D23. As you can't get to the back of the board you will not be able to replace them. (So there is no point in trying to get you to trace the fault down to one of these components.)

Les.

 

The 220 volt reading is probably OK. It should be exactly the same as your mains voltage. The drift from 217 to 220 could be your mains voltage varying. You could confirm that you get the same reading directly on the output of the noise filter. ( Or WITH THE MACHINE UNPLUGGED FROM THE MAINS You could also measure the resistance from the two points where you measured the voltage to the output connections on the noise filter. You should get a very low resistance reading. (Probably less than 1 ohm.)) As you seem to have the required mains input to the board the fault is most likly to be The inductor L1, PTC1 (A thermistor or fuasible resistor.) or one or more of the 4 diodes D20, D21, D22 or D23. As you can't get to the back of the board you will not be able to replace them. (So there is no point in trying to get you to trace the fault down to one of these components.)

Les.

Oh i'll cut it open using an angle grinder. I didnt want to do that before to later find out that it wasnt the board. But now since you've narrowed it down to the board, ill cut it in half to get to the back. If you dont mind, i'd like to proceed.