imac 21.5 820-3126-A 2011 dont power on
The device was brought to me after self-cleaning. After replacing the thermal interfaces, the iMac stopped turning on. While the client was rummaging around in it, he touched the power supply with the processor radiator, after which there was a bang.
I examined the power supply, replaced the burnt-out Zener diode ZD36 and the PWM controller DAP017. Now there are standby 12 and 4 volts
When connecting the board to the power supply, autostart occurs, only LED 501 lights up. The cooler starts to rotate, after half a second it stops and so on in a circle. For these half a second, the main 12 volts appear, other voltages try to rise. I examined the board under a microscope, did not find any knocked-down elements or any obvious faults. All resistances are within normal limits. I took out and reinserted the central processor, took out the discrete video card. The board without peripherals behaves the same way.
The client said that before he shorted the power supply, the device behaved the same way
I examined the power supply, replaced the burnt-out Zener diode ZD36 and the PWM controller DAP017. Now there are standby 12 and 4 volts
When connecting the board to the power supply, autostart occurs, only LED 501 lights up. The cooler starts to rotate, after half a second it stops and so on in a circle. For these half a second, the main 12 volts appear, other voltages try to rise. I examined the board under a microscope, did not find any knocked-down elements or any obvious faults. All resistances are within normal limits. I took out and reinserted the central processor, took out the discrete video card. The board without peripherals behaves the same way.
The client said that before he shorted the power supply, the device behaved the same way
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