perdana main lamp bulb is H4. no need to think about all the rocket science involved. switch on the headlamp, it will light up the top filament hence the low beam. flick to high beam, it will light up the lower filament and u get the high beam.

if it's dim, i guess it's because u r seeing only the small bulb. nak troubleshoot sendiri, cabut the other side bulb, swap and see. confirm rosak, go to spare part shop rm15 je h4 brand biasa2.