Something burned :( how to pin point what died?

[kmaar]

Hi forum,

I’m a first time builder and put together an S4M with following components:

MB: ASUS ROG STRIX Z370i
CPU: i5-8500
SSD: Samsung EVO960
FAN: Noctua l9i
PSU: HDPLEX 400
BRICK: Dell 330 something
GFX: MSI AERO 1060 6GB
NFC machined on/off switch

I assembled it WITHOUT a gfx card cause I hadn’t decided on one yet and it worked fine for weeks. Today I got an MSI aero 1060 and installed it with the nfc riser, plugged it in with the 8pin pci cable that splits into 2x8 pins each with a detachable 2 extra pins and powered it on... what followed was a series of small pops and a small amount of smoke and I unplugged it ASAP after that.
I don’t know what blew but here’s my diagnosis so far:
- Dell psu has a green light when plugged in the wall
- with only the motherboard connected to the HDPLEX400 the motherboard rgb light show is running but it won’t power on

Any ideas what went wrong here?

 

[VegetableStu]

did you follow the facing directions on the riser assembly correctly? it should be printed on the ribbon and the key itself
also visually check for burns on the capacitors and PCIe socket area on both the motherboard and the GPU

 

[kmaar]

did you follow the facing directions on the riser assembly correctly? it should be printed on the ribbon and the key itself
also visually check for burns on the capacitors and PCIe socket area on both the motherboard and the GPU

I don’t see how the riser could be installed wrong? Anyway there's a 8pin mosfet next to the battery connector that seems to have blown I just don't know what I did wrong :/

 

[ExplodingWaffle101]

https://smallformfactor.net/forum/threads/psa-siliflex-riser-instructions.8593/#post-112879

 

[Choidebu]

Must be the riser card. The key AND the cable has directions printed on it.