the set is most likely more cheap chinese junk...  the chinese are just as secretive of their tv products as they are 
of the other *&%^% they sell  
 
  i will try to find some info - though, doubt will be succesful.....
one way of accomplishing the task is to design circuitry to activate the buttons in proper sequence ......
i did this on a cheap zenith (in '94) for display purposes.  how?
upon AC connection a reset pulse was generated for the uP. i  took this pulse through a buffered delay to activate a xistor paralleling the pwr sw. this turned set on . the pwr on xistor (again through a RC delay) would activate a second xistor paralleling the ch up sw ( for ch #).  that perticular set would pwr up on ch 2 whenever there was an AC interuption thus requiring the ch sw activation . ran this set problem free until sold.
this simple mod was easily removed as designed....returning set to original operation.
qrz