AhHa.... I see you removed the heat sink, took the photo, and then took photo's with the heat sink back on.....
In picture at top #5233 the transistor three legs seen on the RIGHT hand side underside is attached to the output tranny, thats the scr
Next pic 5234, that same TO220 is center top of the board, without heat sink.. thats the scr i reckon.
Pic#5 ( last one) shows the TO220 that you are questioning... which I wrongly assumed was the same as the top center one.. ie no heat sink.... I was fooled.
It will be a NPN standard transistor eg 2sc4242 or mje13007 etc. It needs a heat sink, the scr does not.
maybe I got the right one this time.
Is is totally dead, or is there a squeal... if it has a squeal, then likely the scr ... no squeal, likely the npn at least. The flyback diodes are also at risk.
Small ferrite sounds like it should work with those values.. two low ( or split ) impedance ones on the primary, and a hv winding 52r secondary. Two primary ones cause the oscillator to oscillate using the 2sc4242 etc. If you use a tip35 etc, the oscillator will work too well.. the 4242 should be about right for that one. They will be found in many many computer power supplies, or MJE13007 etc
Dead UJT.... unit charges but won't fire, or unit behaving like scr is on all the time.
Dead SCR will be short....will hear the oscillator, but no voltage coming out of the tranny to the cap.
Short flyback... will cycle, but no voltage output.
New fencers are expensive compared to a few dollars worth of parts.