How Regulator with 2 Photocoupler

Working of Regulator with 2 Photocoupler that is :

• Photocoupler N901 - used as a coupling-off control on the regulator by mikrokontrol. Which is set high and low voltage B + (st-by at the B + voltage is low). Control of the pin-37 POWER mikrokontrol → V610 → VD913 V908 → N901.
• Photocoupler N903 - used to control on-off the regulator of X-ray circuit protector. X-ray protector circuit of flyback → VD451 → VD452 → SCR VS472. If the flyback voltage regulator over the job will automatically be turned off by N903
• To disable the X-ray circuit protector, it can be temporarily removed photocoupler N903 first. In normal conditions the voltage at the transistor V474 should be zero.

Regulator Schematics

Trobelshuting there is no voltage for 5v st-by on the secondary :

1. Disable by removing the first circuit protectors N903
2. Check the voltage of 300V
3. Check all transistors
4. Check the start voltage of 300V by R909 >> R906 to the base of transistor power regulator
5. Check the feedback C910 >> R904 (to oscillate)