for dismount of the bolt by a tool when one component inside the casing 21 needs repairing only the lid corresponding the component to be repaired needs dismounting so that the component in question is taken from the casing via the corresponding maintain hole in detail referring to fig4 a and fig4 b when the main board 231 of the electronic unit 23 is to be repaired the first lid 214 is dismounted and then the crew is loosened the electronic unit 23 as a whole slides out of the space 211 along the guiding element 212 and the guiding piece 233 after repairing is completed the electronic unit 23 is placed to its initial position when the tuner 232 of the electronic unit 23 is to be repaired the second lid 216 is dismounted for the user or worker to put his or her hands into the second maintenance hole 215 to take the tuner 232 out for repairing when the bulb needs to be replaced the third lid is dismounted to expose the handle portion 2424 of the set of bulbs 242 the screw fastening the fixed basket 2421 and the movable basket 2422 are loosened to pull out the movable basket 2422 by means of the handle portion 2424 then a new bulb is put in place in the casing when the power supply unit 25 needs repairing only the first lid 214 needs to be dismounted and the bolt is loosened to take out and repair the power supply unit 25 as described above when.