Announcement

Collapse
No announcement yet.

Sanyo dp42840 - Power board cycles and relay clicks

Collapse
X
Collapse
 
  • Page of 1
  • Filter
  • Time
  • Show
Clear All
new posts
Previous template Next
    #1

    Sanyo dp42840 - Power board cycles and relay clicks

    Here is a Sanyo dp42840 that someone already recapped but could not get working. Upon opening it up, I immediately saw a domed Nichicon 1000 uF 16V cap on the power supply. After changing it and checking all other caps on the power supply, I powered it up. All output voltages read OK until it got warmed up and then started cycling and clicking. Sometimes it would get far enough to flash the backlights just for a quick quarter of a second.

    Trying to isolate the problem, I disconnected all other boards and simply did the ps_on jumper to 5V. The board then continues to cycle with nothing hooked up to it. I am now questioning the large caps in the primary main power circuit. There are two 470uF's and they are both reading 420uF. Is this low enough to cause the problems that I am seeing???
    The strong-minded rise to the challenge of their goals,the weak-minded BECOME HATERS

    Tags: None
    #2
    Re: Sanyo dp42840 - Power board cycles and relay clicks

    Maybe; most electronics allow for up to 5% variable; anything over or under that is ruled out of spec in my book; but could be good/in spec as per build quality... I have seen swollen caps on PSUs and the board still gave fine voltages...

    on a side note: id suspect a transistor or transformer failing/failed on the PSU somewhere; pics help...
    Last edited by SlickClick; 06-07-2014, 07:23 AM.

    Comment

      #3
      Re: Sanyo dp42840 - Power board cycles and relay clicks

      Pics of the boards may be coming soon. After re-evaluating the situation. I don't think testing the power board with the PS_on jumper helps on this set. I plugged in all the other boards and, as before, the voltages come on solid for the output. All are present and none are low.
      The strong-minded rise to the challenge of their goals,the weak-minded BECOME HATERS

      Comment

        #4
        Re: Sanyo dp42840 - Power board cycles and relay clicks

        Hi,

        I have seen two of these sets - same model as yours with bad backlights.
        The last one I repaired had the two seconds to black problem and I took the panel apart. There were several bad bulbs in various stages of decline.
        Perhaps you have the same issue and when the lamps warm a bit they trigger the protection circuit.
        I have an inexpensive source for the lamps (18 of them).
        If you send me an e-mail off list we can talk.
        I'm not that far from Pittsburgh.

        Mike

        Comment

          #5
          Re: Sanyo dp42840 - Power board cycles and relay clicks

          This may help also

          http://www.youtube.com/watch?feature...&v=KSYCn93pz6k
          Please upload pictures using attachment function when ask for help on the repair
          http://www.badcaps.net/forum/showthread.php?t=39740

          Comment

            #6
            Re: Sanyo dp42840 - Power board cycles and relay clicks

            I have never really seen back lights themselves go bad maybe once in a laptop from the mid-90s but otherwise the bulbs for the back lighting rarely go bad unless physically broken... But one never knows maybe a large batch of bad bulbs made it into production...

            In all honesty if its a backlighting issue and you can actually still see the image when the unit is on; id take the time to try and retro fit some LED low voltage light strips in place of the bulbs add a small dial to regulate brightness done..! LoL I just said that cause i want to try it but dont have a donor with a backlighting issue yet...

            Again i have a 42 inch sanyo with everything but the LCD screen and T-con took that off to fix another sanyo 42incher and called it my frankenvision; took the display off the backlight housing and out in another sanyo 42 with a different backlighting case/setup... TV works great now too btw... with that said make sure that when you order the bulb you get the right ones cause of the 2 i have it would seem the backlight panel setup is totally different entirely...

            on a side note watch: http://www.youtube.com/watch?v=KSYCn93pz6k
            Last edited by SlickClick; 06-07-2014, 11:17 AM.

            Comment

              #7
              Re: Sanyo dp42840 - Power board cycles and relay clicks

              I watched that video before I got started. I checked all the test points and all is well. I have all voltages and the unit just keeps clicking off then on. Wait about 15 seconds. Click off and on. And so on...
              The bulbs would make sense at this point. Im not going to take it apart that far just to find the bad news. I'll sell it before I do that.
              The strong-minded rise to the challenge of their goals,the weak-minded BECOME HATERS

              Comment

                #8
                Re: Sanyo dp42840 - Power board cycles and relay clicks

                I want to say that if you disconnect the inverter board from the PSU the unit may fire up; since you said the PSU seems to be providing the required voltages...
                If I remember right you can disconnect each bulb from the outside of the case to the Inverter board; disconnect all of those first and try to fire it up... if it comes on and you get and image and sound than you know its a bulb backlight issue if it keeps shutting down try disconnecting the inverter board as previously mentioned... if it still turns off most likely the PSU is bad or the mainboard is bad and is failing the boot check and shutting down... LCD are rather simple to figure out compared to plasmas...

                Comment

                  #9
                  Re: Sanyo dp42840 - Power board cycles and relay clicks

                  I agree that is could be the light bulbs
                  But I have also run into similar problems on several Tv.s going into protection mode
                  and I eventually found out It was just a bad solder joint on power supply
                  I reheated the solder joints on the mosfets and the transformers
                  and everything works fine again.
                  I would try reheating as many solder joints as possible before tearing it farther apart.
                  It might help and hopefully it won't hurt

                  Just and Idea for ya to try

                  Comment

                  Previous template Next
                  Working...
                  X