can anyone tell what diode is this on the midle?it has only yellow ring nothing else.on the left side one is zener BZX85C30 30v 1.3w.
If they are in series (k-k / a-a), then it is a 1S diode (#1) for temperature compensation of the zener.
1N4148, it may be there to block one sense of current flow: the one with the zener forward biased. Tipical in some discrete self oscillating ringing choke converters.