the zoom head should not be the cause of the flash being underpowered... the zoom head only determines the distribution of light...so i think you should try fiddling with the other settings good luck

oh yes you reminded me of a point is that the zoom head only works in 90 degrees position...which means direct flash...anything other than that the zoom head wont work..that might be yr best bet on why it is blinking

hm? it works even when it is titled to any other direction other than the 90 degrees direction? then i dunno oh lidat

if totally cant including 90degrees then i think there must be smth wrong with yr flash...try asking the shop that you bought the flash from...see what they say

the hissing sound is normal...like a bomb wanna explode lidat my nissin flash also lidat... all flash also lidat de...

if a normal working flash, the --mm will show the focal length of yr camera..for eg you turn to 18mm the lcd there will display 18mm and you will hear the flash bulb moving inwards and outwards...