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Old 04-08-2019, 01:38 AM   #85
corellian
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Join Date: Apr 2019
City & State: QLD
My Country: Australia
I'm a: Knowledge Seeker
Posts: 6
Default Re: lg 60pz550 black screen, no power, etc

I have the same model and had to replace 4 Fairchild IGBTs.

Now the unit turns on and stays on but no picture.

Using a block diagram schematic (http://www.toms-service-manuals.com/...&Search=Submit), i disconnected LVDS and shorted control board test pads.

To my joy a clear test pattern emerged! It’s here i noticed the control board led flashing: two long followed by two short blinks. The schematic mentioned if the test pattern is showing but no display then suspect mainboard failure.

So I have been troubleshooting the mainboard as I cannot find a replacement online. Other than a surface mount diode reading a bit strange (in circuit), i cannot find the fault.

I have also tried pulling heatsinks and heating both BGA chips with a heatgun but the same error blinks are showing.

I have done LVDS connector to ground continuity checks and theres quite a few grounds scattered through the pins on the mainboard side but without a schematic I am stuck. All LVDS pins go to the BGA chip without the heatsink on it which I have already tried reflowing anyway.

I think the next step is to try baking the mainboard in an oven but I only have one that goes to 250c.

Alternatively legonch, could you check which pin son your LVDS connector (with the ribbon disconnected) are grounds?

Or would you consider selling me your mainboard?
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