iMac took a hit and won't start - logic board or lcd?

Hi, my imac fell over while it was powered on and now it won’t start. I’m trying to figure out if it’s the logic board or the display itself that needs replacing.

• If I turn it on I can hear the fan at low rpm and the hard drive (fusion) ticking.
• There’s no chime and I have tried numerous attempts to reset the PRAM and SMC.
• There’s nothing on the display. It doesn’t even flicker to suggest there’s power running through it.

Thanks for any suggestions.