LG 50PG20-UA Powering Up then Down

Collapse
X
Collapse
 
  • Page of 1
  • Time
  • Show
Clear All
new posts
Previous template Next
  • dcapper
    Badcaps Veteran
    • Dec 2013
    • 496
    • Canada
    #1

    LG 50PG20-UA Powering Up then Down

    First I had no pic on the lower half of the tv. It was a blown lower driver board that I replaced. Now when I turn the tv on, I get full pic and it then shuts off for a few secs then back on. I read online that the repair kit consists of 6 caps (I tested them all good). Then it says two 18N50's (Pulled them out and metered good, no shorts). But by those 18N50's I found a blown diode 1N5819 (ECG585). I had a ECG587 to test and it popped right away. I see there is an 4 pin IC in a transistor case that the the solder was heated up on. Its an MR4020. I don't see that in any repair kit. Could that be my problem? I have metered every cap, diode, and resistor. The diode that keeps blowing is circled in red and the IC transistor is right below it.
    Attached Files
    Tags: None
    • dcapper
      Badcaps Veteran
      • Dec 2013
      • 496
      • Canada
      #2
      Re: LG 50PG20-UA Powering Up then Down

      I made a mistake. The MR4020 is a 7 pin chip in a TO220 package.

        Comment

        • dcapper
          Badcaps Veteran
          • Dec 2013
          • 496
          • Canada
          #3
          Re: LG 50PG20-UA Powering Up then Down

          If anyone can help, it would be appreciated. I don't think it's the power supply now. I have a draw somewhere. I get a full picture and then it shuts off like a dead short, causes my ups to pop the breaker sometimes. There is 6 ribbon cables that go to the upper and lower driver boards from the screen. If I unplug one of those ribbons, either on the top or bottom driver, the tv stays on, just no pic on lower or upper half of the tv depending on which cable I unplug. Or if I unplug both ribbons from the z-sus board. Could the panel be drawing too much? The picture is fine for the 10-15 seconds its on.

          EDIT: Metering the YSUS at -VY I should be getting 195V but I can't get it over 160V. The cable coming from the power supply is 195v. At -VSC I should be getting 135V and I'm getting 160V and I can't adjust it down. The ZSUS should be 89V at VZB and it is.

          I'm no genius but can a YSUS board be bad even though it shows a picture?
          Last edited by dcapper; 01-29-2014, 01:01 AM.

            Comment

            • freakaftr8
              Badcaps Legend
              • Oct 2012
              • 3743
              • USA
              #4
              Re: LG 50PG20-UA Powering Up then Down

              I bet that Ic is shorted. Seems to happen on samsung power supplies. That 4 pin is a voltage regulator. Replace it when in doubt. The diode is in that circuit off the regulator.
              Did I leave the soldering iron on?

                Comment

                • dcapper
                  Badcaps Veteran
                  • Dec 2013
                  • 496
                  • Canada
                  #5
                  Re: LG 50PG20-UA Powering Up then Down

                  Thanks. But I think its the YSUS now. I adjusted it as best as I could get it and the tv was on for 30 mins. Now just a relay clicks and the power light is going red and blue. This is from the service training manual.

                  12V Short: Power LED is lit Red in stand by. At Power On, Power LED flashes 2 times Blue then 1 Long Blue goes back to Red. Relay clicks off immediately.

                  But when I unplug the YSUS the tv powers up ok.

                  Too bad these boards are $120.

                    Comment

                    • dcapper
                      Badcaps Veteran
                      • Dec 2013
                      • 496
                      • Canada
                      #6
                      Re: LG 50PG20-UA Powering Up then Down

                      Well this thread can be closed. After metering pretty much everything in the tv, I found out it wasn't the tv. Well the lower buffer was still bad. Anyways I had it plugged into a small UPS. The UPS was faulty. TV works as it should.

                        Comment

                        Previous template Next

                        Related Topics

                        Collapse
                        • valvashon
                          LG 55UH6150- trouble powering up, then half lit screen (pictures!)
                          by valvashon
                          The 55" LG has been in the basement for a few months without being used. Turned it on yesterday, set came on as it should and showed a complete screen for about 5 seconds (was on a broadcast channel but no antenna was connected), then the screen went mostly dark with about 1/3 of the screen on the right lighting up with brighter lines in that lit part (sorry, no pictures of that). Power LED was cycling too, preventing the TV from fully powering up.
                          Pulled the back off, all boards looked OK. Pulled the LED connector, turned the set on to see if it would power up but I don't belive it...
                          11-24-2024, 12:08 PM
                        • DarKHawK
                          Asus 2021 ROG Strix G17 G713 not powering on and not charging.
                          by DarKHawK
                          Hi,

                          I have an Asus 2021 ROG Strix G17 G713 that is not powering on and not charging. Board number is G533-6050A3250201.
                          When plugged in, I found that the 3.3v/5v regulator was getting extremely hot, so I removed, next I found a short on the 3.3V rail. Removed the two 3.3v mosfets and found one of them shorted, but still the short on the rail did not clear. Then I injected voltage at that rail, and found out that U60400 the 2.5v rail was also getting hot. Removing it changed the short from 0 ohms to about 5-6 ohms, then I remove a bunch of other suspect components but that did...
                          07-11-2025, 05:24 AM
                        • serious_electron
                          Strange! Acer laptop not powering on but charging the battery (orange light on when charger and battery plugged in).
                          by serious_electron
                          Hello Everyone!

                          I have an Acer Aspire A315-42 laptop. I generally leave it on for long time by closing down its lid (so it enters the sleep mode). Recently, it rained quite heavily in out area. And the humidity and moisture seem to be high. So one late evening, after I opened the lid and turned on the laptop, it did power on as the blue light turned on but after it booted to the desktop screen, just 5-10 seconds after both the screen and blue light went out and laptop shut down (the blue power light turned orange). And after 2-4 seconds that orange light went off and the laptop died.                          ...
                          06-28-2025, 02:57 PM
                        • ShadowAi12
                          ASUS ROG STRIX B550-F GAMING — Board not powering on properly
                          by ShadowAi12
                          Hi,
                          I recently bought an ASUS ROG STRIX B550-F GAMING motherboard that was listed as "dead, not powering on." However, it does show some signs of life. I've performed several basic measurements and would like to share the results.
                          • The board enters a "ready to power on" state after plugging in the PSU.
                          • Pressing the power button increases power draw.
                          • Sometimes, touching the RSMRST_L pad with a multimeter probe causes the board to shut off and return to standby.
                          Measurements:
                          (taken after pressing the power button, while the board is attempting to start)
                          • H_SKTOOC#
                          ...
                          06-11-2025, 01:05 PM
                        • TechSplendid
                          MacBook A2442 not powering on – suspecting CD3217, but replacement didn’t help
                          by TechSplendid
                          Hi All,

                          I'm working on a MacBook Pro A2442 (14", 2021) that's not powering on. On two out of three USB-C ports, I get 5V and the current briefly ramps up to around 0.210A before dropping to 0.036A. On the third port (JF600), I only get 0.0045A and it stays there.

                          Initially, I suspected a faulty CD3217 on that port, especially since I noticed signs of previous liquid damage near the JF600 USB connector. I replaced the CD3217 with an UF400 (from an A2442 donor board from the same location). According to the supplier, this should be a compatible version, but the behavior...
                          04-09-2025, 02:13 AM
                        • Loading...
                        • No more items.
                        Working...