LAMBDA PS
One from two coolers was bad.
Overheat 5.1R => 5,6R, PCB and int. print to cooler's supply.
Fuse F15A, MOC8101 => CNY17 -4;
LM239 (voltage switching)
LM358 (control PS in module)
Corrosion, screws. 
Was unqualified repair.
For inspection PWM 2*BUZ71 the PS must be loaded.