Troubleshooting backlight inverter short to ground

Collapse
X
 
  • Time
  • Show
Clear All
new posts
  • DLinkOZ
    Badcaps Veteran
    • May 2013
    • 238
    • USA

    #1

    Troubleshooting backlight inverter short to ground

    Is there a good resource posted on this forum for this? I have an RCA L42FHD37 with a bad backlight inverter (6632L-0481A), and wanted to see if it was worth it/possible to hunt down the component failure. In the second picture, the two groupings of test points are shorted - the bottom 2 are positive and lead to the smd fuse below, the upper two are ground.

    What I can find is in the group of 4 transistors just under the caps, two appear to be shorted. However, I realize it could be reading back from some other point in the circuit.

    Case this be tested in-circuit?
    Attached Files
  • bammbammfran
    Badcaps Veteran
    • Apr 2014
    • 476
    • USA

    #2
    Re: Troubleshooting backlight inverter short to ground

    The transistors do not appear to have cooked, But , One still could have gone out
    There is a chance that one of the two ceramic capacitors between the one electrolytic capacitor and the one resistor went out, Those might be the easier ones to check first
    But, With a dead short like this, you will more than likely have to remove parts.

    Not sure what type of tester you have, but if it is a manual select, try dialing it up till you actually see resistance between the pos and neg on the board, even if it is miniscule. then recheck ground to ground and see if pos to ground is a little different, If it is a little different, then you may be able to locate the issue using this resitance reference

    Comment

    • DLinkOZ
      Badcaps Veteran
      • May 2013
      • 238
      • USA

      #3
      Re: Troubleshooting backlight inverter short to ground

      Thanks, I'll check it out.

      Comment

      • DLinkOZ
        Badcaps Veteran
        • May 2013
        • 238
        • USA

        #4
        Re: Troubleshooting backlight inverter short to ground

        I ended up doing a quick and dirty little test - I lifted one of the legs on two suspect transistors, and the short went away. So I suppose I can swap those out and move on.

        Comment

        • tom66
          EVs Rule
          • Apr 2011
          • 32560
          • UK

          #5
          Re: Troubleshooting backlight inverter short to ground

          Not always - sometimes the driver IC will be damaged so you should consider replacing that too.
          Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
          For service manual, schematic, boardview (board view), datasheet, cad - use our search.

          Comment

          Related Topics

          Collapse

          • playit
            450watt power supply 5v, 3.3v short to ground wire,in output rail ,connectors
            by playit
            hello everyone , working zebronics power suply 450 watts , 5v ,3.3v givin short to ground black wire, also in circuit at output, resistor was charred but shows right values , after removing resistors 39ohms, 51 ohms, there was no short , no continuity beeps with ground , but after replacing new resistors (now i am not switching it on) ,again short still exists . when i put bigger ohm resistor like 100k ohm , no short beeping sound comes , lower ohm resistor gives continuity beeps ,other big ones donest , as its a working psu , i am confused what to remove now or how to go further now .
            ...
            09-02-2023, 02:43 AM
          • Superbee_dad
            Sharp 80” long short flash backlight error - Help
            by Superbee_dad
            Hello Sharp TV experts
            Our Sharp LC-80LE642U displays one short one long flash error code which is a backlight error. I went into service mode and there were 8 lamp error counts recorded. I reset the count to 0 and did a reset. The last monitor error cause was 16 B00014639:12. 16 is the code for backlight error. I tried to power the tv up but went back into error mode.

            > I checked voltages on the power supply board and they all check out .. including 3.28 volts at the error pin.
            > There is power to the cpu and T-CONN and no faults found there. The cpu has a flashing...
            01-24-2025, 11:51 PM
          • MisterAIL
            820-00840 / No boot / PP3V3_G3H Short to ground
            by MisterAIL
            Hello everyone,

            Firstly sorry for my english, french guy inside.

            I brought a macbook pro A1708 - 820-00840 logic board, wasn't powering on.
            History is a day, nothing happened when opening the laptop.

            Nothing special inside, no corrosion, no liquid damage, never opened.

            First, with the logicboard alone on the desk, mesures are :
            5v017 and 0.000 amp. nothing else.
            Finding a short on the PP3V3_G3H_VR, but not on the PP3V3_G3H (0.540 on diode mode), PPDCIN_G3H_CHGR_R present (5,1 volts) PPVIN_G3H_P3V3G3H around 4.1 volts. PM_EN_P3V3_G3H...
            10-13-2021, 11:42 AM
          • triplefour
            UN65TU700DF picture and sound but no backlight. BL tests ok but repl. PSU didnt fix!
            by triplefour
            this tv is throwing me for a loop. do samsung tvs no longer have the backlight self test feature built into the power supply?
            i tested the backlight with my LED tester and it lights up both strips. one of them reads 100v and the other reads 63.7v.
            unplugged mainboard from power supply but left backlight plugged in, and then plugged psu wall power in. expected to see backlights light up but see nothing.
            according to how ive diagnosed in the past, this would almost always be a bad power supply. replacement power supply was cheap like 20$ from ebay. but still i get not even...
            09-13-2023, 10:43 PM
          • Saturn49
            Barely perceptible flicker on Pixelbook
            by Saturn49
            TL;DR: Fixed a board by replacing the display connector and traces for the backlight. Now backlight sorta flickers.

            Side Note: This is mostly an exercise in stretching my troubleshooting and micro-soldering abilities - Pixelbooks aren't worth much, though I do have a replacement on order because my wife still uses it pretty often.

            Background: Coffee was spilled onto the display connector of a Google Pixelbook which (of course) managed to short out the display backlight. This burned the connector on the main board and the cable. In fact, it burned two pads for the connector...
            12-02-2023, 05:28 PM
          • Loading...
          • No more items.
          Working...