Hi, I just put together a new desktop, the video card is a Sapphire Radeon RX 580 8 GB PULSE. It's on a b450 msi motherboard, with a ryzen 2600 processor (so no onboard/integrated graphics).
I have a monitor connected to the card via DVI, and it works fine. Then I have a displayport monitor to connect with hdmi, but it gets no signal.
I know the display works (can plug it into my macbook with an apple hdmi/dp cable). Have reseated the video card and other components several times for various reasons. Always this problem.
Maybe the cable is bad (it's actually an hdmihdmi cable with a displayport adapter). But I don't have other cables lying around to compare - is there any other troubleshooting that can be done, e.g. with a multimeter should I be able to get some particular voltage on some contacts of the hdmi out? Or is there a hdmi good-cable test? I remember doing that stuff back in VGA days.
Should the Radeon software (or even the windows device manager) be able to tell me if it even perceives the hdmi port?
I just want to know if the hdmi outs are even working before I go and order a new cable.. 
Obviously I am new to this
(Adding to suspicion about the card: sometimes after a reset, POST fails on the vga check. Then I have to unplug everything, wait a while, plug in, then it's all fine again... so I am suspicious of this card).
thanks a lot
