(1) Phenomenon: There is no light
Please observe the LED indicator on the IGBT board under weak current test. If it is flashing, maybe it’s due to the bad
quality of the absorption circuit, resulting in line burst with a large current. If the LED is always off, then maybe the reasons are as  follows:
(a): SG2525 is damaged;
(b): The circuit around the SG2525 is damaged, showing as a result of welding or component damage.
(2) Phenomenon: There is no count for light
(a): IGBT burst (or the pad had melted around the fixed screw);
(b): Photocoupler damage on IGBT;
(c): The output pulse signal on the motherboard does not work (D27 or R16 is damaged).