Never opened up a slim one, carried out surgery on about 12 of the old fat ones.
never seen that problem though.
usually they stay on but do f all so you can go into diagnostic mode.
dont know if its the same on the slims, but on the old ones pressing the eject button and wireless link buttom at the same time starts disgnostics, it'll give some lights on the power button, press the 2 buttons again and a new light display will appear, etc. you should get 4 sets to give a 4 digit code (1 light, 3, 2,1) etc then look up online what the number means