You have come to the right person:
all parts in this model for the convergence are located on middle board.
If set comes on and shuts off (green power light goes out) do the self check: press and hold (you may know or have done this) both the menu and input buttons for at least 5 seconds and release both.
Power light will blink a 2 digit error code like 2 blinks, 2 blinks a pause and repeat it several times.
That is short protect and a 98% chance one or both (usually one) of the two pico fuses that protect the convergence circuit have blown.
I will add some photos here one of the single IC this set uses for this, one of the protect resistors in front and to one side of it, and one showing the pico fuses (ones for the chip are circled)
A note= I have fixed a lot of these and have composed instructions which are based on doing it---tell you everything you will need and how to do the repair from start to finish--step by step.
I will not post them here as other experts will copy them and I spent some real time composing them.
If you want they are free--provide me a email address and I will forward them to you for free.
I have fixed almost a thousand of these sets (Mitsubishi) with this problem.
Copy and save the photos and let me know (you can post a comment here) if you have questions or want the instructions.
the photo for the fuses will not load---on middle board to left and towards the rear--green and location numbers 9fao4 and 05--both are marked 5 amp,.