Another 55LV500-UA Turns on. No Backlights. No Sound

[culcuhain]

Ok. Here is what we have. My guess is bad main.
Plugged in.. Red Standby light comes on. Turn On. Hear Click. Red Standy. goes to Warm white. >>NO << quick flash of back lights.

Voltages below (format stolen from recent 55LV5000 thread)...
In Standby
Pin..........Label..........Voltage
1.........POWER-ON......0
2->4........24V..........0
3->8........GND...........0
9->12......3.5V...........3.52
13->15....GND...........0
16.......VSYNC-IN.......0
17,19,21...12V.........0
18.........DRV-ON........0
20,23........NC............0
22...........PWM..........0
24.........ERROR.........0

Turned On
Pin..........Label..........Voltage
1.........POWER-ON......3.42
2->4........24V..........24.7
3->8........GND...........0
9->12......3.5V...........3.52
13->15....GND...........0
16.......VSYNC-IN.......0
17,19,21...12V.........11.9
18.........DRV-ON........0.003
20,23........NC............0
22...........PWM..........3.2
24.........ERROR.........0

Jumpered Power-On to 3.5 and 3.5 to Drv-ON and backlights come on.

Bad main not sending the DRV-On signal?
To me it looks like the

[budm]

Re: Another 55LV500-UA Turns on. No Backlights. No Sound

Since you can force the backlights to come on by disconnecting the DRV-ON that goes back to the main board and all other cables are in place. Do you see the pictures on the screen and all other functions are OK? If not then you have more than just bad DRV-ON command signal.

[culcuhain]

Re: Another 55LV500-UA Turns on. No Backlights. No Sound

Thank you for the quick response. All cables connected. 3.5v jumpered to Drv-on. Tv still goes to standby. When powered on. Backlights come on. No image is displayed. No volts across fuse on T-con fuse. No amps across fuse on T-con. No volts feeding fuse on T-con. I am pretty certain bad main board. Any reason why I could be wrong?

[tvtimmy]

Re: Another 55LV500-UA Turns on. No Backlights. No Sound

Take out the mainboard and remove the heatsink and rubber pad. Use a heat gun on LOW and heat the entire chip for about 45 seconds. Let cool, put it in and it will work. For how long, nobody knows. I gave one to a cousin and its still running after 16 months.

[culcuhain]

Re: Another 55LV500-UA Turns on. No Backlights. No Sound

45s at 220C and no change. ��

[Nick's Tvs]

Re: Another 55LV500-UA Turns on. No Backlights. No Sound

The components on your board are not meant to be heated above 105 degrees for long periods of time. Solder melts at about 180c so obviously they should be able to withstand those temperatures for short periods of time. But I would not suggest trying to fix your board on your own as your chances of not doing it right are much higher than a successful repair. You have a BGA failure on your main board most likely and will need to get it serviced. I would just hope that what you have done so far has not damaged the board beyond repair. At those temperatures, you will melt solder and some of the components on the back of the board could have fallen off. Additionally, if the cpu chip sank in due to heating the chip and the solder balls below it as well, you could have created a short which would cause ram failures as well.

[culcuhain]

Re: Another 55LV500-UA Turns on. No Backlights. No Sound

New mainboard installed last night. All is fixed.

[budm]

Re: Another 55LV500-UA Turns on. No Backlights. No Sound

Thanks for the follow-up on the repair.