1 Display shutting off on iMac randomly.
Hello all. Thanks for reading.
2017 iMac a1419 EMC 3069. Sat for 3 years, used to work fine. Upon poweringy it on, it works for a bit and then the display shuts off. Anywhere from 10 seconds to 5 minutes later. Rest of the computer stays working. No backlight or image that I could see with flashlight. When this happens, diagnostic lights 4 and 5 shut off.
Sometimes when booting, lights 4 and 5 never come on, and screen stays dark
I’ve tried replacing the blade ssd and hard drive, reseated all connectors, reseated CPU, etc.
I’ve tried an external monitor via usb-c to hdmi adapter, but it never works. I’ve wiped the drive, so I’m not getting to a login screen. I’ve heard that external will only work at login screen and after.
I’ve replace the NVRAM backup battery. Reset nvram, smc.
USB devices like keyboard and mouse work fine.
I’m trying to determine if it’s the lcd panel or the logic board. I’m quite proficient in electronic repairs, but I’ve not done much with Macs.
Any ideas? Thanks in advance.
Tom
329 
971 