troubleshooting TV SMPS sequence

Collapse
X
Collapse
+ More Options
Posts
 
  • Time
  • Show
Clear All
new posts
  • ilikesteel
    Badcaps Veteran
    • Jul 2012
    • 284
    • usa

    #181
    Re: troubleshooting TV SMPS sequence

    CApLeaker,

    Thanks again. it was a great learning experience for me. I think I developed some extra troubleshooting skills because of it.

    thanks again.

    ilikesteel

    Comment

    • CapLeaker
      Leaking Member
      • Dec 2014
      • 8061
      • Canada

      #182
      Re: troubleshooting TV SMPS sequence

      Your welcome!

      Comment

      • budm
        Badcaps Legend
        • Feb 2010
        • 40746
        • USA

        #183
        Re: troubleshooting TV SMPS sequence

        Originally posted by CapLeaker
        because the LD7550B IC12 is the PWM for the other transformer where Vcc for the PFC comes from and it also does the power friendly 5V rail. That C44 is the starting cap, r77 is the starting resistor.
        See it as 2 PSU's. One that is switched on and off (12/24V) and the other for 5V that runs continuously and is also some ecofriendly version PWM.

        I cannot explain why there was 360V on the main filter cap while the PFC is in the off condition. I didn't read the whole TDA16888 datasheet through.
        I did not read from the beginning to see if he has unstable 5VSTBY or not, but the clue was when he reported the fluctuation for the TDA VCC, if he looks at Q1 switched transistor on the feeding side he would probably see the fluctuation there too, and I believe the the voltage fluctuation was higher than 14V but his meter was not fast enough to show that but it was enough to get the TDA IC be running on and off so the main cap was charging and discharging, if he looks at the VCC with scope he will probably see what the actual Voltage really is.
        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

        • ilikesteel
          Badcaps Veteran
          • Jul 2012
          • 284
          • usa

          #184
          Re: troubleshooting TV SMPS sequence

          BudM,

          Thanks Budm, great job you and everyone. the first time I checked the 5vsb with the scope on the small1W board, there was alot of signal distortion sitting on top of the 5.36V going just below 5V. I did change the cap C616 on the 1W board and that cleared up the distortion.

          what you're saying is there are two 5V stndby voltages, one on 1W board and another on the PS itself?

          anyway, glad I made it through the storm. your tireless efforts on so many posts is unbelievable. glad you kept an eye out on mine!

          ilikesteel

          Comment

          • budm
            Badcaps Legend
            • Feb 2010
            • 40746
            • USA

            #185
            Re: troubleshooting TV SMPS sequence

            The set up in this RCA is not typical, it has the 1W external standby power supply that supplies the STBY to run the main board and for driving the power replay that will supply 120Vac to run the main power supply board, they could have done without that 1Wpower supply.
            T2 is the standby power transformer but in this case it not being used as STBY because it is not always on, that transformer is the one that supplies the power to run the TDA chip as shown in the diagram.
            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

            Related Topics

            Collapse

            • madan1
              Troubleshooting half-bridge smps
              by madan1
              Hello everyone, I'm trying to fix what seems to be a half-bridge smps.
              The switching controller is sg2525a, which I have replaced with a brand new sg3525a. The low and high mosfets are 1c27ac 6n50. The mosfet driver is IRS2301S.
              Both mosfets were tested outside circuit with a component tester and seem to be fine.
              With oscilloscope I see ~65khz switching signal on both low and high outputs of the controller, but on the output of the mosfet driver there is switchig signal only on the low output (flat line on the high output).
              So I guess the mosfet driver is faulty?
              ...
              01-23-2025, 06:05 AM
            • PantherDave
              Microsoft Surface Pro (5th gen) model 1796 - no power
              by PantherDave
              Hi all!

              I'm trying to troubleshoot a Microsoft Surface Pro (5th gen) model 1796 that won't power on. Motherboard model is M1007506-015. My priority is retrieving data, but the SSD is integrated so it looks like if I can't repair it it'll need to go to a data recovery company. I've done a little basic board repair before, but nothing this advanced until now. So please forgive my ignorance in advance. 😅

              I found the boardview for this laptop in the forums here, and am able to open it on my PC with FlexBV.
              https://www.badcaps.net/forum/troubl...-hardware-devi...
              05-29-2024, 02:01 PM
            • dkneyle
              Onkyo DX-V500 Laser Disc Player - weird SMPS fault
              by dkneyle
              This relic from a technology path that came to a dead end (but still has historical interest) was brought in with a dead SMPS, which is based around a MK1210 device. I got it going after a battle. It seems to have a strange design - if it's not getting feedback that the secondary is OK it cause the big FET to go into full conduction and overloads resulting in a blown fuse at best or something worse! I'm using a Dim Bulb Tester (70W/230V) which thankfully has saved the day a number of times whilst repairing.

              Now, it loads a CD OK. The motor voltage output (which is built onto the SMPS...
              02-01-2022, 02:08 AM
            • ShadowAi
              ASUS TUF X570-PLUS doesn't power on: no VRM_EN signal.
              by ShadowAi
              Hello, I have an issue with the motherboard. Specifically, it doesn't power on, more precisely, the POST initialization doesn't occur.

              Let me start from the beginning, the motherboard suddenly stopped working one day. There are no beep signals from the speaker, and the debug LEDs are not lighting up. After inspecting it under a microscope and using thermal imaging, I didn't find anything that could be damaged.

              After that, I began voltage measurements, in which I noticed the absence of VDDQ, VDDP, VTT, and VPP lines. Later, I checked if there is an EN state on these lines,...
              03-15-2024, 10:46 AM
            • blues_spirit
              practical courses for troubleshooting pc motherboards
              by blues_spirit
              Hello from France,
              mon2 kindly advised me to post a thread to ask the question(s) I'm concerned about. I'm new to the forum and I'm looking for practical courses for troubleshooting pc motherboards especially laptops in Europe, if possible in France. I have been a computer network system administrator and a corrector of administration modules for automated programs under Unix. But I really miss the practical "ops" side of troubleshooting. So I would like to start from the beginning: 1.8V, 3.3V, 5V and 19V tests for example, etc...
              Do you think this is feasible for me? I...
              12-18-2022, 12:56 PM
            • Loading...
            • No more items.
            Working...