As above noted, various types of {HEAD ~ current snubber circuits} provide an alternate discharge path from the bottom end of primary 16 to divert {TAIL ~ the leakage inductance energy} away from the collector of Q3 and thus protect the latter against the avalanche and secondary breakdown failures and thermal runaway at turn off 
As above noted , various types of { HEAD ~ current snubber circuits } provide an alternate discharge path from the bottom end of primary 16 to divert { TAIL ~ the leakage inductance energy } away from the collector of Q3 and thus protect the latter against the avalanche and secondary breakdown failures and thermal runaway at turn off
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH