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lg 32LC46 backlight inverter board fault

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  • dskall
    replied
    Re: lg 32LC46 backlight inverter board fault

    Originally posted by jimbofz View Post
    im like a dog with a bone
    Well, it's good you didn't bury it and just keep gnawing on it.

    Leave a comment:


  • jimbofz
    replied
    Re: lg 32LC46 backlight inverter board fault

    Originally posted by dick_barton View Post
    Well done. Persistance paid off.
    im like a dog with a bone

    Leave a comment:


  • dick_barton
    replied
    Re: lg 32LC46 backlight inverter board fault

    Well done. Persistance paid off.

    Leave a comment:


  • jimbofz
    replied
    Re: lg 32LC46 backlight inverter board fault

    finally fixed inverter board fault
    47 ohm r76 was o/c causing shading left to right
    its across d12

    Leave a comment:


  • jimbofz
    replied
    Re: lg 32LC46 backlight inverter board fault

    Originally posted by Biruslapio View Post
    The voltages sent from main board are correct, it is the inverter that is at fault, maybe even a replacement board costing around 7 USD is not worth it on UK? Plus there's shipping.

    What about those 0 OHM resistors, are they fine? There should be no voltage drop on any of them, not much else to suggest here.
    thanks for trying all zero ohm components checked
    still a work in progress ,i will post the results

    Leave a comment:


  • Biruslapio
    replied
    Re: lg 32LC46 backlight inverter board fault

    The voltages sent from main board are correct, it is the inverter that is at fault, maybe even a replacement board costing around 7 USD is not worth it on UK? Plus there's shipping.

    What about those 0 OHM resistors, are they fine? There should be no voltage drop on any of them, not much else to suggest here.

    Leave a comment:


  • jimbofz
    replied
    Re: lg 32LC46 backlight inverter board fault

    replacing board ? wheres the fun in that ,
    this tv is only worth peanuts due to its age
    but i enjoy the challenge of fault finding down to component level .
    its the best way to learn
    and this tv despite its age ic capable of good clear hd pics
    seasons greetings to all

    Leave a comment:


  • jimbofz
    replied
    Re: lg 32LC46 backlight inverter board fault

    Originally posted by biruslapio View Post
    that's probably the forum's auto resizer.

    So you must have an inverter fault, there is no way all the lamps aged uniformly and got darker on one side.

    What's the voltage on error, on/off, i-pwm and e-pwm?

    One of these pwm voltages controls the lamp brightness, if this is the same as other old lg lcds, 3.3v should be maximum brightness, and less than 0.8v it doesn't even turn on.

    These wires that you used for bypassing the error pin, they're too long, try using the least amount of wire you can, if nothing changes, i suggest replacing the inverter board, it's cheap at least.
    e pwm =4.1v i pwm= 3.3v on/off=4.9v error =0v

    Leave a comment:


  • lotas
    replied
    Re: lg 32LC46 backlight inverter board fault

    This inverter suffers from poor soldering of smd components (resistors, capacitors ...) try to solder the whole board well.

    Leave a comment:


  • Biruslapio
    replied
    Re: lg 32LC46 backlight inverter board fault

    That's probably the forum's auto resizer.

    So you must have an inverter fault, there is no way all the lamps aged uniformly and got darker on one side.

    What's the voltage on ERROR, ON/OFF, I-PWM and E-PWM?

    One of these PWM voltages controls the lamp brightness, if this is the same as other old LG LCDs, 3.3V should be maximum brightness, and less than 0.8V it doesn't even turn on.

    These wires that you used for bypassing the error pin, they're too long, try using the least amount of wire you can, if nothing changes, I suggest replacing the inverter board, it's cheap at least.

    Leave a comment:


  • jimbofz
    replied
    Re: lg 32LC46 backlight inverter board fault

    i will try again
    spin them then upload again
    nope that didnt work im confused?
    Attached Files

    Leave a comment:


  • jimbofz
    replied
    Re: lg 32LC46 backlight inverter board fault

    yes i suspect low voltage.
    the ccfl,s are not u shaped
    all connections to each end of them were checked
    the "earthy" end should have return voltage on cct shown as AA 1,8v
    but its only .2v
    here are some pics
    i dont understand why pics are upside down ,i check their orientation before upload and they are correct ?
    Attached Files

    Leave a comment:


  • Biruslapio
    replied
    Re: lg 32LC46 backlight inverter board fault

    Post a picture of the issue.

    Are these lamps U shaped or do they end up fitting into at a long vertical metal on the opposite side of the chassi? If they are darker might be too low voltage, or bad connection in one of the sides.

    Leave a comment:


  • jimbofz
    replied
    Re: lg 32LC46 backlight inverter board fault

    Originally posted by Biruslapio View Post
    is the LCD darker or the lamps themselves? If the lamps + polarization sheets are ok then it's a t-con or panel problem.
    thanks
    i see where you are going with this
    but i cant get inverter to start without overriding the protection, as posted earlier.this is why i was focusing on the inverter board
    when i opened it up to examine ccfl,s they looked fine just darker at left side than the right ,
    i did expect to see one that was out ,
    causing prot to cut out b/l but no they were fine
    i also checked the foils to see if they were causing the shading
    but they all looked fine when i gently flexed them
    if fault was t con or panel ,i dont think it would kill the b/l
    would you agree?
    its a head scratcher

    Leave a comment:


  • Biruslapio
    replied
    Re: lg 32LC46 backlight inverter board fault

    is the LCD darker or the lamps themselves? If the lamps + polarization sheets are ok then it's a t-con or panel problem.

    Leave a comment:


  • jimbofz
    replied
    Re: lg 32LC46 backlight inverter board fault

    Originally posted by Biruslapio View Post
    Are the voltages across the fuses the same?
    I undestood that there's a gradient effect in the CCFLs, from top to bottom or the opposite, is that it?
    all fuses 24v supply fine pic dark on left then gradual increase to perfect pic on right

    Leave a comment:


  • Biruslapio
    replied
    Re: lg 32LC46 backlight inverter board fault

    Are the voltages across the fuses the same?
    I undestood that there's a gradient effect in the CCFLs, from top to bottom or the opposite, is that it?

    Leave a comment:


  • jimbofz
    replied
    Re: lg 32LC46 backlight inverter board fault

    the voltage shown on cct for return end of ccfl,s is 1.8v this is only .2v
    the 5v supplied via q2 is ok at 4,9v
    pin 14 of u2 should be 4.4v its 3.7v
    this goes to u3 pin 14 shown as dim
    this is fed via 100k r50 which measures fine
    any ideas please

    Leave a comment:


  • jimbofz
    replied
    Re: lg 32LC46 backlight inverter board fault

    Originally posted by lotas View Post
    Inverter circuit.
    many thanks Lotas

    Leave a comment:


  • lotas
    replied
    Re: lg 32LC46 backlight inverter board fault

    Inverter circuit.
    Attached Files

    Leave a comment:

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