I never liked the HDMI interface, there are far too many iterations for my liking. I went from D-Sub to DVI then skipped HDMI and went straight to Display Port. Older HDMI displays are notoriously problematic to use with newer HDMI standard boards/GPUs. I doubt it killed your monitor but it is possible it pushed it over an edge it was already heading to. Even if it were the case, it would have happened no matter what newer standard device you connected to it. 

This is why I stick to DVI when available or Display Port for higher res/refresh, DVI always works and DP is not far behind in my experience. 

Although your monitor broke down I can confirm the issue with my AB 350 Gaming ITX/ac and a Sony TV. The TV model is from 2009 and it seems to me that the board uses some kind of weird display mode the HDMI inputs of my Screen can not handle. The picture is shifted until Windows 10 and the Radeon Drivers are loaded. Therefore I can only reasonably change my uefi settings when I use my more recent Dell monitor.

hdmi is 5volts

feel free to use voltmeter

Good news:

The replacement board came with 4.70 installed, and booted up out of the box.  It also very easily handled overclocking the memory to it's rated speed.

Bad news:

Unlike every other system I've had over the past many years, the HDMI port hates my current monitor.  (A 24" Dynex TV.)  The HDMI display is shifted to the right, leaving a good quarter of the screen blank (i.e., I can see all the BIOS options, but the not the verbose explanations on the right side.)

This appears to be exclusive to this monitor, as HDMI seems to work fine on other TV displays in the house.  It is, however, still super disappointing.  (Yeah, I can use VGA, but I don't want to.)

Haven't done enough digging to find out if this is something that might be corrected with an update.

Feels like a situation of so close, yet so far.

There's really no reason it should be doing this.

I fully agree with the cheaper to RMA angle. With the prices of RAM these days the motherboard is often cheaper to swap out. 

Let us know how the replacement works out for you. 

On a side note, I tend to avoid both Gigabyte and MSI boards, I have had nothing but issues with them in the past. Gigabyte BIOSes tend to have issues and be rather unpleasant to use and MSI have had quite a few issues with quality on the lower end (b350 counts as lower end). In the end, it's all down to your experience with a manufacturer. Whatever you chose, be sure to check reviews (both tech sites and user reviews like on newegg/amazon). Any recurring issues need to be investigated. 

Good luck 

That said, yes, I think it probably all comes down to specific BIOS versions.  Until I can get things up and running, I've no idea what I'm working with.  4.5 may not have the same memory compatibility as 4.7 or 4.82.  *shrug*

Sadly, it's easier and cheaper to replace the board with one that accepts the components I have, versus playing the slots (heh) trying to find memory this board likes enough.

(Currently, I'm returning the board to NewEgg as defective, and replacing it with the same model.  But if this continues, yeah, I'm gonna have to jump ship to Gigabyte or MSI.)

And then there's the boot loop.  Which throws a little bit of doubt on the memory as a culprit.

Because -- and correct me if I'm wrong -- especially with no memory, wouldn't the system simply hang at boot, trying to throw a beep code (assuming they're enabled by default), as opposed to rebooting?

do you have any local small independant computer shop near you ?

might be an idea to take board and cpu into one with a big smile and ask advice

most independant shops are willing to help for future business .............

With Ryzen, history has taught me to always suspect RAM. If RMAing the board is less of an ordeal than finding more RAM to test for you then go for it.

Let us know how it goes and good luck 

RAM being used is Patriot Viper 4 Series 3000Mhz 8GB Dual Channel Kit (2x4GB), Model PV48G300C6K.

Not strictly verified on the QVL for this board, but other users' experiences show it should work fine, if everything has been updated properly.  (I'd have to go digging again to give sources...)

Anyway, since my last post, I've pulled the entire board from the case: nothing on the board but CPU, cooler & RAM, 24+8pin, speaker, and power switch jumper only.  Tested with 1 and 2 RAM modules, and NO modules.  Tested with different PSU, as well.

No change in behavior.  Still no POST, no beep codes, 30 second power cycles.

At this stage it could only be the CPU, or the board.  And I'm leaning toward the board.

Only thing I haven't done is reseat the CPU, something for which there should never be a need to do.

EDIT:  I can now say that I've reseated the CPU, with no change in behavior.

Without alternate RAM to test, and my belief that this RAM should work, I'm not sure what to do except RMA the board, and hope for better results with its replacement.