GA-Z170 MX stopped working five long beeps

[GrandDadTexas]

GA-Z170 MX
G Skill Ripjaws V PC4-17000 8Gx2 DDR4-2133  Two of them Slot 1 and 3
Intel I5-6600K 3.5 GHZ 6MB Cache LGA1151
EVGA 500 Watt power
Cooler Master
Gigabyte GV-RX480G1 Gaming 4GD video card
Samsung SSD

Dad helping son after his build.

New equipment
Booted
Installed W10
Internet worked
10 hours of use and it will not boot. Has five long beeps. No video.

Removed video card and used on board graphics = 5 long beeps, no boot, no video
Removed 1 of 2 memory sticks; used slot 1 = 5 long beeps
Did same with second memory stick = 5 long beeps gone but no boot or video
Tried slot 3 & 4 with 2 sticks = 5 beeps
Tried slot 3 with one card - slot 4 = 5 beeps the other stick no beeps
Tried different power supply and monitor =did not work
Checked processor for damage, no evidence of overheating, cooler master fan working, reset processor = 5 long beeps

Suggestions please. Thank you.

[shadowsports]

5 long beeps..  usually ram or CPU.  If you have reseated all hardware in the previously working system, try the following:

-CLR_CMOS with button and jumper if equipped (power should be disconnected, battery remains installed) Test
-Remove power, CLR-CMOS, press and hold power button for 10 sec, then remove battery, replace after 2-3 min, retest
-If the board is equipped with BIOS_SW, change from dual to single and BIOS 2, test boot

Long shot..  test MB battery voltage, if low replace. 

Reseating devices is usually enough to reset the BIOS if it has become corrupt for whatever reason.  Forcing start up from second BIOS is also helpful in these situations.  You've already gone the extra step of testing with different PSU, onboard GPU and display.  It could be the CPU, but I understand testing would be difficult if not impossible.  If nothing else has been changed, I'd return the MB for replacement with retailer. 

Edit***

Since this board does not have BIOS switches, the following methods can be used to invoke the back up BIOS.

Method#1:
1. Shut off the power supply using the switch on the back of the PSU, wait 10-15 seconds.
2. Press and hold the case Power On switch, then while still holding turn on the power supply from the switch on the rear.
3. Still holding the case power on switch, the board will start, once it does release the case power on switch and shut off the power supply via the switch on the read of the unit. (Do the latter two parts as quickly as you can once the board starts)
4. The board will shut down.
5. Turn the power supply back on using the switch on the rear of the unit.
6. Turn on the motherboard by pressing the case power on button.

Method#2
1. Shut your PC down
2. Hold the power button until the PC starts and shuts down again
3. Press the power button again, your backup BIOS should kick in now and should re-flash the main BIOS if there's anything wrong with it.

Method #3:
1. Shut your PC down
2. Hold the power AND the reset button for about 10 sec, than release.
3. Backup BIOS should kick in anytime soon now.

[GrandDadTexas]

Great instructions but did not work. Was bad ram AND damaged motherboard. I spent so much time troubleshooting that I or 15 year old (new builders" bent a few pins. Went to computer store to buy tiny tweezers (I used to be a watchmaker) and sales person shook their head and said "good luck". Not wanting to put more time into this I bought a new board and memory. Computer went together in an hour. I'll fix the pins and give it to a young person saying "don't get your hopes up but if it works  . . .enjoy". Told the new builders Rule 1: Read the manual then follow the manual Rule 2 Touch the inside of a computer like it is a bomb waiting to explode. Thanks for the quick reply.

[shadowsports]

Bending pins in the CPU socket or memory slot can happen.  Especially the memory slots which are extremely difficult to straighten or repair.  This is probably why the guy selling you the tweezers said, "good luck".  Its a hard lesson, but I'll bet it never happens to you again.  Glad you got everything working.  Good little system I'm sure he'll enjoy.

Cheers!