🚀 go-pugleaf

After my airconditioner failed the other day, and being reluctant to pay 
a technician to come and fix it, I've been taking a look at its 
electronics board.

It's clear that its power supply circuit has failed. From the board 
itself I've inferred this partial circuit:

http://members.optusnet.com.au/sylviae/smps.jpg

I am pretty sure there are no other components connected to the 
transistor labelled Q1, and it is this transistor that has failed. The 
failure mode is a short (a few ohms, polarity insensitive) from base to 
emitter. The collector is open circuit. The transistor is thus unable to 
sink enough current to prevent the switching transistor from turning on, 
and as a result the 8.2 Ohm fusible resistor has also failed.

It seems moderately likely that by replacing these two components I can 
get the board working again.

The circuit nevertheless puzzles me. The function of Q1 appears to be to 
  bias the switching transistor. But this seems to rely somewhat on the 
characteristics of the two transistors, which I would have thought was 
asking for trouble. In particular, it looks to me as if Q1 could simply 
prevent the switching transistor from ever conducting, and nothing would 
happen.

Is this an accepted technique? Or have I misunderstood the purpose of Q1?

BTW, this is from the external unit of a nine year old Daikin split system.

Sylvia.