Hi!
I was wondering if I could get a bit of advice. My Powerpoint 32" LCD TV has given up the ghost. When turned on, after ~5sec the backlit attempts to power up. Instead it "fizzles" for about 1sec, then cuts out after a brief flash. Using a flashlight, an image can still be seen on the screen.
So the backlight isnt getting powered up. I opened up the TV and found a MLT666B power supply board. This was powering the backlight inverter circuit with 24v, according to the markings on the board (see pic). Measuring across this using a multimeter, i noticed that there was 24v on this rail, but after the 5sec after power up, then the tv attempted to power up the inverter, the 24v rail becomes unstable and dies to 0v within a second.
Two of the CrapXon capacitors on the secondary stage of the supply board were bulging on the top. Even though these were on the 5v rail, i decided to replace all the capacitors on the secondary stage of power supply with some panasonic low ESRs caps I found on Ebay.
The problem is, this didnt work. The 24v rail was still unstable. I connected up my tabletop power supply and fed 24v @ 3amp to the backlight inverter and found that the TV powered up fine after the 5seconds. It displayed an image on the screen perfectly with little or no noise from the backlight inverter. I also connected a load of two car 12v headlamps in series with the 24 rail of the board and found that they briefly flashed as soon as the tv was powered, but died after 1seconds, not even attempting to light on the 5seconds mark. This confirms that the 24v rail on the PSU isnt working.
So as I am at a bit of a loss, I was wondering if anyone has any other suggestions of what else I could test on the power supply board? If so, how would I go about doing it? Thanks!!
For anyone interested, or for future reference for anyone using this board, I have also included the BOM for the secondary capacitors and a circuit diagram/schematic of the MLT666 board.
I was wondering if I could get a bit of advice. My Powerpoint 32" LCD TV has given up the ghost. When turned on, after ~5sec the backlit attempts to power up. Instead it "fizzles" for about 1sec, then cuts out after a brief flash. Using a flashlight, an image can still be seen on the screen.
So the backlight isnt getting powered up. I opened up the TV and found a MLT666B power supply board. This was powering the backlight inverter circuit with 24v, according to the markings on the board (see pic). Measuring across this using a multimeter, i noticed that there was 24v on this rail, but after the 5sec after power up, then the tv attempted to power up the inverter, the 24v rail becomes unstable and dies to 0v within a second.
Two of the CrapXon capacitors on the secondary stage of the supply board were bulging on the top. Even though these were on the 5v rail, i decided to replace all the capacitors on the secondary stage of power supply with some panasonic low ESRs caps I found on Ebay.
The problem is, this didnt work. The 24v rail was still unstable. I connected up my tabletop power supply and fed 24v @ 3amp to the backlight inverter and found that the TV powered up fine after the 5seconds. It displayed an image on the screen perfectly with little or no noise from the backlight inverter. I also connected a load of two car 12v headlamps in series with the 24 rail of the board and found that they briefly flashed as soon as the tv was powered, but died after 1seconds, not even attempting to light on the 5seconds mark. This confirms that the 24v rail on the PSU isnt working.
So as I am at a bit of a loss, I was wondering if anyone has any other suggestions of what else I could test on the power supply board? If so, how would I go about doing it? Thanks!!
For anyone interested, or for future reference for anyone using this board, I have also included the BOM for the secondary capacitors and a circuit diagram/schematic of the MLT666 board.
Attached Files
But today, I’m making an exception here. Why? No idea. Perhaps only because the repair details are still “fresh” in my head… which is ironic, given this is a 16 year old monitor that hardly anyone will care about today. It is new to me, though. 
I picked it up last November from someone on my local Craigslist. It wasn’t very close to where I live, but was close to a family friend that I had to go visit anyways. So after watching the posting on Craigslist for a few weeks and seeing it getting...
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