Announcement

Collapse
No announcement yet.

Focal Cub 3 won't start

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    Focal Cub 3 won't start

    Hello everybody,

    I have an issue on my Focal Cub 3 subwoofer unit : it stays desperately off.

    The main fuse and the 2 MOSFET's are not blown.

    Here is a picture of the main psu board :



    As you can see on the picture, the 2 MOSFET's are driven by a tiny pcb board vertically soldered on the main pcb board "INDIGO 660038RA".



    From left to right, the pin 5 and 8 are connected to the gates of the MOSFET's.


    As I saw weird colors on the resistors, I changed all the resistors, all the diodes and all the capacitors on the tiny pcb board. The DB6 diac (hard to find !) and the MPSA92 transistor are the only survivors...

    I even replaced the 2 MOSFET's with IRF740 (IRF730 originally)...

    After replacing all that components, the voltages on the pin of the board are still the same...

    From left to right :

    120V
    350V
    119V
    119V
    119V (-> gate MOSFET)
    0V
    0V
    0V (-> gate MOSFET)

    It changed nothing.


    One day, as I was doing some tests, I don't know what happened but the unit started...

    I measured the following on the pins.

    From left to right :

    166V
    342V
    87V
    150V
    179V (+ square wave with the oscilloscope)
    -20V
    15V
    +20V (+ square wave with the oscilloscope)


    As I had to leave home, I turned the unit off and when I came back... nothing... and still nothing since that "holy" day...


    I go on with my investigation...

    Now, I'm wondering what is the purpose of an area of the main pcb : the 240V is directly connected thru 2 (X1 Y1) capacitors to the secondary. I guess this is a "step down circuit"... The value of the 2 capacitors is 100pF. I don't know which voltage I should have after this two capacitors... and I don't know what should be my reference point for measurement. Currently I have 0V between the GND and the OUT pins of both L79(78)15CV regulators.
    I regret not to have done some measurements on the regulators the only day it worked...


    Here are the top view and the bottom view of this part.





    According to you what should I measure in the different areas of this part ?

    Would it be interesting to change the X1, Y1 capacitors ?


    It is hard to me to understand the whole operation of this unit...




    Any help will be appreciated.

    Thanks a lot !
    Attached Files
    Last edited by Per Hansson; 08-05-2018, 07:01 AM. Reason: Offsite images uploaded

    #2
    Re: Focal Cub 3 won't start

    conductive brown glue must be removed.and then replace startup cap.
    need to see bottom to find out what smps chip it has

    Comment


      #3
      Re: Focal Cub 3 won't start

      Since the gate of the mosfet isn't getting anything, I am also for the start up capacitor and the PWM. If you measure around the primary of the PSU the negative lead is on the negative of the main filter capacitor. Measuring on the secondary it is GND.
      Last edited by CapLeaker; 01-31-2016, 05:03 PM.

      Comment


        #4
        Re: Focal Cub 3 won't start

        The start up capacitors : do you mean the two X1, Y1 (blue ones) just between the heatsink screw and the 2 red capacitors ?

        What about the smps chip ? I thought the square wave was generated by the diac/capacitor association in the INDIGO tiny pcb board... Could you be more specific about this PWM chip I should looking for please ?

        Thank you very much for your quick reply !

        Comment


          #5
          Re: Focal Cub 3 won't start

          Can we see the whole bottom of the PSU?
          Last edited by CapLeaker; 01-31-2016, 06:26 PM.

          Comment


            #6
            Re: Focal Cub 3 won't start

            Just to be clear, you at the beginning you were not getting any DCV at that white connector with grey wires that go to the preamp/auto ON/OFF control board?

            'Would it be interesting to change the X1, Y1 capacitors ?' The circuit does not need X/Y caps to function.
            Most sub woofer will stay in standby mode until it detects the audio signal at the inputs, and it will go back to standby 15 minutes if the signal is no longer present.
            Never stop learning
            Basic LCD TV and Monitor troubleshooting guides.
            http://www.badcaps.net/forum/showthr...956#post305956

            Voltage Regulator (LDO) testing:
            http://www.badcaps.net/forum/showthr...999#post300999

            Inverter testing using old CFL:
            http://www.badcaps.net/forum/showthr...er+testing+cfl

            Tear down pictures : Hit the ">" Show Albums and stories" on the left side
            http://s807.photobucket.com/user/budm/library/

            TV Factory reset codes listing:
            http://www.badcaps.net/forum/showthread.php?t=24809

            Comment


              #7
              Re: Focal Cub 3 won't start

              I'm not at home this week so I can not take any photo of the bottom of the pcb... But I can tell you that there is no chip at the bottom ; this is a double sided pcb but the components are only located at one side.

              At the white connector, there were no DC voltage...

              I would like to add that there is a switch on the preamp board that allows to choose between auto On/Off mode and "always On" mode. I always switch to always ON not to have that parameter to handle with...

              If the subwoofer is able to start from a signal from the source, what is the utility of this sided circuit with 2 caps ? Isn't it to get the stand-by mode ?

              Many thanks.

              Comment


                #8
                Re: Focal Cub 3 won't start

                It looks like more than one companies use this BASH amplifier module:
                http://www.teleservice-depannage.com...0.htm?start=15

                http://www.diysmps.com/forums/showth...PS-DIY-Rebuild

                https://community.klipsch.com/index....repair-thread/
                Never stop learning
                Basic LCD TV and Monitor troubleshooting guides.
                http://www.badcaps.net/forum/showthr...956#post305956

                Voltage Regulator (LDO) testing:
                http://www.badcaps.net/forum/showthr...999#post300999

                Inverter testing using old CFL:
                http://www.badcaps.net/forum/showthr...er+testing+cfl

                Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                http://s807.photobucket.com/user/budm/library/

                TV Factory reset codes listing:
                http://www.badcaps.net/forum/showthread.php?t=24809

                Comment


                  #9
                  Re: Focal Cub 3 won't start

                  You are right, the problem is however different of mine because the units have got blown fusés or shorted transistors...


                  Could someone confirm me that the start-up caps are the two blue ones with glue please ?

                  Thank you.

                  Comment


                    #10
                    Re: Focal Cub 3 won't start

                    Originally posted by frankie31 View Post
                    You are right, the problem is however different of mine because the units have got blown fusés or shorted transistors...


                    Could someone confirm me that the start-up caps are the two blue ones with glue please ?

                    Thank you.
                    Those two blue caps are safety cap, nothing to do with operation of the unit, they can be removed and the unit should still function.
                    Never stop learning
                    Basic LCD TV and Monitor troubleshooting guides.
                    http://www.badcaps.net/forum/showthr...956#post305956

                    Voltage Regulator (LDO) testing:
                    http://www.badcaps.net/forum/showthr...999#post300999

                    Inverter testing using old CFL:
                    http://www.badcaps.net/forum/showthr...er+testing+cfl

                    Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                    http://s807.photobucket.com/user/budm/library/

                    TV Factory reset codes listing:
                    http://www.badcaps.net/forum/showthread.php?t=24809

                    Comment


                      #11
                      Re: Focal Cub 3 won't start

                      We need straight shot and well focused pictures of the whole bottom side and top side of the board to see how the circuits are wired up.
                      Last edited by budm; 02-02-2016, 10:17 AM.
                      Never stop learning
                      Basic LCD TV and Monitor troubleshooting guides.
                      http://www.badcaps.net/forum/showthr...956#post305956

                      Voltage Regulator (LDO) testing:
                      http://www.badcaps.net/forum/showthr...999#post300999

                      Inverter testing using old CFL:
                      http://www.badcaps.net/forum/showthr...er+testing+cfl

                      Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                      http://s807.photobucket.com/user/budm/library/

                      TV Factory reset codes listing:
                      http://www.badcaps.net/forum/showthread.php?t=24809

                      Comment


                        #12
                        Re: Focal Cub 3 won't start

                        try this!!
                        http://thompdale.com/bash_amplifier/bash_amp.htm

                        Comment


                          #13
                          Re: Focal Cub 3 won't start

                          Looks like the super-primitive self oscillating half bridge design often used in halogen lamp PSU.
                          No regulation, very little protection.
                          There is no electrolytic "start up capacitor" so stop looking for that. Check all of the high value resistors on the primary side, these can fail open. The Diac might be faulty too. Also some of the zener diodes on that vertical board might be bad if the FETs ever have failed.

                          Comment


                            #14
                            Re: Focal Cub 3 won't start

                            Thanks a lot for all your answers.

                            Ok, I will give you the pictures this week-end.


                            About the diac ; someone told me to check the diac as follows : I need to quickly short-circuit the diac (< 0.5 second) : if the supply starts... the diac is failing.

                            What do you think about that method ?


                            Thanks again !

                            Comment


                              #15
                              Re: Focal Cub 3 won't start

                              Shorting the Diac: yes, should work, just do it quickly. And carefully, its at mains potential after all...
                              I would have a good look at the large (47k as it looks) resistor above the VDR. These like to drift upwards. Unsolder to check it.

                              Comment


                                #16
                                Re: Focal Cub 3 won't start

                                Hi everybody !

                                Sorry for my late reply...

                                And the winner is... the DIAC !!! After quickly shorting the diac... the unit powers on !!

                                Now I'm waiting for my DIAC DB6 order... 1 month...



                                I still don't understand how the circuit works... Do you think it has something related to this ?

                                What about the "protection circuit" with X1, Y1 capacitors ? What use is it ?


                                Thank you very much for your help !

                                Comment


                                  #17
                                  Re: Focal Cub 3 won't start

                                  X1, Y1 are safety caps, not need to function, they are used for line noise filter to pass compliance test.
                                  Never stop learning
                                  Basic LCD TV and Monitor troubleshooting guides.
                                  http://www.badcaps.net/forum/showthr...956#post305956

                                  Voltage Regulator (LDO) testing:
                                  http://www.badcaps.net/forum/showthr...999#post300999

                                  Inverter testing using old CFL:
                                  http://www.badcaps.net/forum/showthr...er+testing+cfl

                                  Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                                  http://s807.photobucket.com/user/budm/library/

                                  TV Factory reset codes listing:
                                  http://www.badcaps.net/forum/showthread.php?t=24809

                                  Comment


                                    #18
                                    Re: Focal Cub 3 won't start

                                    Ok I got it for X1, Y1 blue caps !


                                    And what about the DIAC dimmer circuit ?

                                    Thank you

                                    Comment


                                      #19
                                      Re: Focal Cub 3 won't start

                                      http://www.diysmps.com/forums/showth...PS-DIY-Rebuild
                                      I cannot tell but the diagram can be drawn based the PCB that OP has made.
                                      Never stop learning
                                      Basic LCD TV and Monitor troubleshooting guides.
                                      http://www.badcaps.net/forum/showthr...956#post305956

                                      Voltage Regulator (LDO) testing:
                                      http://www.badcaps.net/forum/showthr...999#post300999

                                      Inverter testing using old CFL:
                                      http://www.badcaps.net/forum/showthr...er+testing+cfl

                                      Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                                      http://s807.photobucket.com/user/budm/library/

                                      TV Factory reset codes listing:
                                      http://www.badcaps.net/forum/showthread.php?t=24809

                                      Comment


                                        #20
                                        Re: Focal Cub 3 won't start

                                        Hello everybody, sorry I'm late, last week I bought a PSB subseries 1, it was like 15 bucks so of course it doesn't work, as I opened it someone tried to repair it so I don't know what he changed, the thing is I know there are 2 irf730 just in front of the "daughter" wich have been raplaced with p12nm50n (don't know why), and I'm not shure if the "lateral" mosfets have been replaced too, on the left (watching the board from the side of AC input) it is irf9530 and the right irf6040, again sorry for beeing so late and thanks!

                                        Comment

                                        Working...
                                        X