No Display Signal

Hello, I'm getting No Display Signal on a Windows 10 Pro PC with an ASUS HD Radeon 7750 graphics card and I'm pretty sure I know exactly what caused the problem, but I don't know how to fix it.

This PC has worked perfectly for about 1.5 years in its current configuration. The only change I made was I replaced the HDMI cable from the graphics card to the monitor with a DisplayPort cable in order to free up the HDMI port on the monitor for something else. Immediately, the PC refused to power up. After checking cable connections I took out the DisplayPort and re-connected the original HDMI, and the PC instantly whirred to life with all the usual hard drive noises, only now it was sending no signal to the monitor.

I had purchased the DP cable from Amazon on the basis of over a thousand 5-star reviews, but upon returning to the sales page I found several 1 star reviews stating that the cable was uncertified and had an extra pin wired up that could damage some graphics cards. Given that my PC seems to have short circuited immediately after connecting it, that sounds highly likely to be the culprit.

Since then, after much googling, I have tried:
- Different ports on the same video card.
- replacing the video card with another video card.
- removing the card and using the on-board vga port.
- different monitors (I've confirmed that the original works fine).
- holding down the power button for a minute before booting.
- cleaning and replacing all RAM.
- pulling the cmos battery.
- hard resetting the mother board with the jumper.

Nothing worked. Also, after reading a response to the same question posted elsewhere here, I tried booting with no RAM installed, and there was no warning beep, which I read means that the mother board may be damaged. Do they all reliably beep under those conditions? It's an ASUS P8Z77-V LK mother board, for what it's worth.

So I guess my 2 part question is:
1. Is there anything left to try with my current equipment? And...
2. If I replace the mother board with a new board of the same type, keeping everything else the same, does that alone sound likely to solve the problem (if in fact the mother board is shot)?

I'm not completely inept at tinkering with hardware, but I'm mostly the plug-and-pray type. I've never worked with a mother board that someone else hasn't set up first.

Much appreciation in advance to anybody taking the time to read all this and offer any advice.