samir, by your wiring description looks like #1 is for the feedback loop that the lamp is on (lit) and #4 is most likely lamp enabled. Remember that this TV used to shut down if the lamp did not work etc. So with your conversion you most likely do not have that feedback loop. You will have to get a schematic and trace those wires and see where they connect and what senses the signal. Most likely a transistor on the board.
May be you can narrow it down by running the error code check. Potentially it could tell you exactly which part of the missing feedback circuitry is shutting it down. Error Code Operational Check
Note: The TV must be in “Shut Down” and not have been switched Off, to perform the Error Code Operational
Check. When the TV is switched Off, the code automatically resets to “12” No Error.
Pressing the front panel “INPUT” and “MENU” buttons at the same time, and holding for 5 seconds,
activates the Error Code Mode. The LED flashes denoting a two digit Error Code, or indicating no problem
has occured since the last Initalization.
Note: The front panel buttons must be used, NOT those on the Remote Control.
• The number of flashes indicates the value of the MSD (tens digit) of the Error Code.
• The flashing then pauses for approximately 1/2 second.
• The LED then flashes indicating the value of the LSD (ones digit) of the Error Code.
• The Error Code is repeated a total of 5 times.
Example: If the Error Code is “23”, the LED will flash two times, pause, and then flash three times.