the two scrs are making some kind of triac, maintaining the full ac phase.
Humm maybe not totally phase controlled, somekind of pwm controling
The supplies i have seen, are sniffing the ac phase, and adjust accordingly ... doesn't seem the case here ?
Check the auxiliary supply unit,
ground are #15, #14, #8
vcc on point #16 should be around 50volts ?? , and after on point #2 around 30vdc
BUT there is a symetrical supply of +15vdc and -15 vdc as shown and written, but the common point ground is #5
I think they use floating grounds in the psu, be careful you may have some falses values because of that, it depends where you probe on the boards.
The scr control board is floating on the - o/p output connector ... so does the two other boards, because of the second transformer.
Pin#5 on the control amplifier board is ground for that board, #8 is +15vdc, #1 is -15vdc
Your huge serie pass transistor E, B C should be tested disconnected from the circuit, check your d23 and d24 output diode for short, conductivity or leakage ...
Did you connect something on it before it gone smoking ?? had bad experience with inductive loads before, my Kepco psu went berserk, modified to add supplemental protections ..