I have a 30" Cinema Display (A1083) that will not light up and there is no picture visable when I shine a light on it. The monitor was checked with a known good power supply. I disassembled the display and had a look inside. There is no service manual for it so I used this as a reference http://monitor.espec.ws/files/lg_26lh201c-za_chassis_ld91a_svcmnls_207.pdf
The metal chassis that the main board attaches to is grounded and was used for all checks.
Checked the black 5 pin connector.
Found 24v on the two pins on the left, Ground on the two pins on the right and 1.9v on the centre pin.
Checked the 5 pin connecor with smaller wires to the right of the black 5 pin power connector. Found 4.95v on the far left pin, 5V on all others except the second from the right (brown) which was ground.
Checked for power on the inverter board and found 24V before and after the 8A fuse. There is power and ground on either side of the four capacitors and transistors on the inverter board. There are three pads on the inverter board.
There is no voltage on the on/off pad .
There is 2v on the vbr pad and no voltage on the status pad.
The inverter board appears to have the power needed to operate, but is not getting the on signal from the main board.
Checked continuity through the wiring harness from the main board to the inverter board -ok
Disconnected at the main board: status LED, Firewire and USB in, Firewire and USB out, the monitor input from the display board and checked for backlighting -no go.
Disconnected the inverter board connector at the main board, connected the display connector and checked for picture with no back light. -no go.
Replaced the main board with no change.
According to the other LG diagnostic manual for the TV, The symptoms point to a failed inverter board.
Do you have helpful input?
I'll post what happens next and the normal readings when I have it up and running.
The metal chassis that the main board attaches to is grounded and was used for all checks.
Checked the black 5 pin connector.
Found 24v on the two pins on the left, Ground on the two pins on the right and 1.9v on the centre pin.
Checked the 5 pin connecor with smaller wires to the right of the black 5 pin power connector. Found 4.95v on the far left pin, 5V on all others except the second from the right (brown) which was ground.
Checked for power on the inverter board and found 24V before and after the 8A fuse. There is power and ground on either side of the four capacitors and transistors on the inverter board. There are three pads on the inverter board.
There is no voltage on the on/off pad .
There is 2v on the vbr pad and no voltage on the status pad.
The inverter board appears to have the power needed to operate, but is not getting the on signal from the main board.
Checked continuity through the wiring harness from the main board to the inverter board -ok
Disconnected at the main board: status LED, Firewire and USB in, Firewire and USB out, the monitor input from the display board and checked for backlighting -no go.
Disconnected the inverter board connector at the main board, connected the display connector and checked for picture with no back light. -no go.
Replaced the main board with no change.
According to the other LG diagnostic manual for the TV, The symptoms point to a failed inverter board.
Do you have helpful input?
I'll post what happens next and the normal readings when I have it up and running.