LG 32LX2R only 5V standby voltage (YP2632t PSU)

Collapse
X
 
  • Time
  • Show
Clear All
new posts
  • Dannyx
    CertifiedAxhole
    • Aug 2016
    • 3912
    • Romania

    #1

    LG 32LX2R only 5V standby voltage (YP2632t PSU)

    Good day folks. As the title says, I've got this YP2632T power board from an LG TV that won't power on. Couldn't find the schematic, so that would be greatly appreciated as well. The standby LED comes on, but that's about it....I removed the power supply and tried turning it on 'manually' by applying 5V to the ON/OFF pin (standard stuff): the relay clicks and the main cap C102 charges up to around 400V, but the secondary stays dead: no volts other than STBY. I could tell no "switching action" was going on because I couldn't hear anything AT ALL (SMPSs usually make a slight hissing sound when operating).
    Many sources suggest replacing every single cap on the secondary, but I find it hard to believe that it would cause the board to turn on, since the problem is somewhere in the primary I believe. I DID replace the 3 small 47uF caps (C105 thru 107) that are part of the startup circuit and the 5VSB ones (C221-C222), but still nothing. SOMETIMES, I'd get 6v on the 12v bus, but nothing on the others, so it's like "half-working". I checked the 3 ICs in the primary: IC101, IC302 and IC303. The first 2 are FAN7601 MOSFET drivers. The last one (on the right in the picture (IC303) is a MIC4423. The first FAN (IC101) seems to operate normally, as it drives the standby circuit which puts out 5v accordingly. The second FAN (IC302) does get 10.4V on its VCC pin, but I don't know what it's supposed to drive after that, since its OUT pin doesn't go to one of the 2 remaining FETs like I expected, instead, it goes through a diode (D307) to the VCC pin of the MIC (IC303). Well, that pin is dead (no power). It seems to me the OUT of IC302 is rectified by that SMD diode and used as the supply for IC303...what a freak setup >_> This is also why I believe IC302 might be faulty and not putting out anything on its OUT pin, which in turn prevents IC303 from starting the switching action. Another mystery is how the second MOSFET (Q102) is driven, since its gate pin doesn't seem to go to any of the ICs - it loops back to the source through some resistors and diodes :|
    To further make this more annoying and complicated than it should be, it's one of those bullsh!t double-sided boards which are extremely hard to follow and you have to keep flipping it around It seems a fairly common problem, but mine's a bit different that others I found. Any thoughts ? Let me know if you need close-ups of any other part of the board.
    Attached Files
    Wattevah...
  • jose almeida tavares
    New Member
    • May 2011
    • 8

    #2
    Re: LG 32LX2R only 5V standby voltage (YP2632t PSU)

    Hello, friend, the problem is solved? in this case the component replaced? thanks.

    Comment

    • nomoresonys
      Badcaps Legend
      • Jan 2013
      • 12085
      • U.S.

      #3
      Re: LG 32LX2R only 5V standby voltage (YP2632t PSU)

      Ok, and what component was it??

      Comment

      • Dannyx
        CertifiedAxhole
        • Aug 2016
        • 3912
        • Romania

        #4
        Re: LG 32LX2R only 5V standby voltage (YP2632t PSU)

        No, I don't think I managed to get it going, otherwise I would've posted the follow-up, unfortunately
        Wattevah...

        Comment

        • nomoresonys
          Badcaps Legend
          • Jan 2013
          • 12085
          • U.S.

          #5
          Re: LG 32LX2R only 5V standby voltage (YP2632t PSU)

          My bad Danny, I should have quoted jose almeida tavares, he said he fixed it but didn't explain what component it was.

          Comment

          • Dannyx
            CertifiedAxhole
            • Aug 2016
            • 3912
            • Romania

            #6
            Re: LG 32LX2R only 5V standby voltage (YP2632t PSU)

            No, I don't think he fixed it - from what I understand, he asked the same thing
            Wattevah...

            Comment

            • nomoresonys
              Badcaps Legend
              • Jan 2013
              • 12085
              • U.S.

              #7
              Re: LG 32LX2R only 5V standby voltage (YP2632t PSU)

              Oh, lol, I see now, it was a question.

              Comment

              Related Topics

              Collapse

              • tvguy12012012120
                Zombie Samsung UN55NU6900F dead / no standby voltage - randomly came to life after hours of troubleshooting then died
                by tvguy12012012120
                This is my first attempt at troubleshooting a board like this, I know I could just buy a new board but I'm curious to figure out how this works. I've been testing different components in the evenings this week and I think the problem is with the IC failing to start up for some reason. When the board is plugged in there is no standby voltage.

                Then today it randomly sprung to life like a zombie but shortly died thereafter. I have no idea why it would have done that and its the first time I've seen it running. I discharged capacitors on the board last night, then it was sitting today....
                02-07-2025, 05:13 PM
              • fharris1977
                Vizio D50u-D1 Dead Set No Standby
                by fharris1977
                Hi. I got a Vizio with no power or standby, and won't turn on with remote or button. I checked the voltages on the connector and all read 0.00V or nearly 0(0.050 ON/OFF pin). None of the pins are labeled STB for standby although I do see some 5V pins. Other than the obvious standby led, which isn't coming on, is there a way to check for standby voltage on this PS. I'm trying to see if my problem is the PS or mainboard. Some Vizios I have fixed with no standby led me to think it was the PS but it turned out being the mainboard. Any experience with this set would be greatly appreciated.
                12-28-2023, 10:25 AM
              • Crystaleyes
                Samsung BN44-00259A standby question
                by Crystaleyes
                Hi all.

                I started a thread while back regarding TV power supply standby circuitry as it is something I am not quite on top of.
                SMPS theory and function is becoming more familiar, however the standby part is still a bit of a mystery.

                Anyway, a friend has this TV with the above mentioned power supply board which has no standby voltage, nor any other voltages leaving the board.
                The mains AC comes in fine, gets filtered and rectified with power is on the main filter cap as well as the transformer and drain pins of the ICE3B0665J, but that's it.
                ...
                08-11-2023, 05:15 AM
              • reessi
                JSK4228-050 Power Supply Standby voltage changing! (Possible from Wharfedale LTF37K1)
                by reessi
                Hello,

                I am trying to re-purpose this power supply that I saved years ago from a tv with a cracked screen for a monitor but that is not really that relevent at the moment. I do not recall which tv but a google search looks like it is from Wharfedale LTF37K1.

                You may notice I made some alterations moving some components to the top and some wires which are from a 5v regulator I fitted to the 12v output as the monitor requires 5v. The standby was already at fault from the beginning, it has nothing to do with the alterations...

                Years ago it had some bulging caps...
                04-26-2021, 11:42 AM
              • psssst
                Yamaha TSX 120 Standby Problem
                by psssst
                Hello forum. I've recently been given a Yamaha TSX 120 DAB radio and ipod dock. Its working well however when put on standby its using 6.3 watts. The manual states less than 1 watt on standby. I measured this with a plug in monitor which seems accurate with other items. In use it uses around 7.5 watts. Firstly has anyone who owns a similar radio also got a plug in monitor to check if this is normal with this unit? In the first half a second the monitor shows 0.3 watts which I suspect is what it should use but something is switching it to be almost fully powered. I've searched the manual for eco...
                03-01-2024, 07:25 AM
              • Loading...
              • No more items.
              Working...