LGP4247-10 Power Supply Failure

Discussion in 'General Electronics Chat' started by Ryan Amfahr Longhorn, Jun 21, 2015.

  1. Ryan Amfahr Longhorn

    Thread Starter New Member

    Jun 21, 2015
    Hi everyone, this is my first post.

    I have an LG 55LE5400 TV that's worked fine until a few days ago. No storms, nothing to cause a power surge (that I know of), but last week while my wife and I were reading, we heard a POP and saw a flash behind the TV. I pulled out the power supply (picture attached) and the fuse lower left of the board was blown. I went to our local electronics store and bought a handful of replacement fuses. The first one I put in blew the instant I connected power.

    I've just gotten into electronic repair and I'm pretty sure that after testing the capacitors I'm above my head. I didn't plan to have my first project be a 55 inch TV.

    So, I'm hoping someone here can help me out. I've got a DMM, plenty of patience, and if I wasn't motivated to learn before, I sure am now in light of possibly having to buy a new TV or a new power supply. I'd rather find the screwy part and replace it than spend loads of cash for a 25 cent piece of equipment.

    Thanks is advance.

    (I checked the SMPS tutorial as well and am not sure whether it applies to me or not)
  2. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
    First off let's 'rule out' the most probable etiology --- to wit: shorted electrolytic capacitor{s}:

    Prior to consideration of the following, it is advisable that you first make a visual inspection then check each cap with a VOM or LCR indicator for obvious shorts, leakage, etc...

    Please be advised that faulty (cip shorted) electrolytics occasionally read 'normally' at the low EMF supplied by a VOM or LCR indicator... Although, in the case of an LCR reading, the capacitance will usually measure far out of tolerance...

    You may properly test each capacitor via application of the rated EMF through an appropriate current limiting resistor -- A persistent, significant drop across the resistor indicates a shorted or objectionably 'leaky' capacitor...
    Should you lack a power supply suited to the above method, you will need to employ the substitution technique -- The best policy is to 'swap out' all 'likely suspects' with new caps -- note that said procedure is often more economical than it may seem...

    Please keep us posted!:)

    Best regards
  3. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    Welcome to AAC.
    First discharge all the capacitors using a low value resistor.
    Then with a DMM in diode range check for dead shorts across the caps, the Bridge and all the FET's and diodes that are mounted on the heat sink.
    Post the result
    I am sure atleast one is dead short.
    Label them on your diagram and post the pic. Much easier than way to understand.
    One picture is worth a few threads.