Hi all, after some tech advice, apologies if this is not the right forum, but any help would be appreciated. Basic problem I'm having: When I turn on my mac pro, the light comes on and it seems to boot up, but the monitor has no connection with it. The monitor is working (I've tested it with my laptop). It literally gives me the 'No connection' message on screen. As of today, Mac won't boot up at all. Details: I recently moved to the US from Australia and just had my MacPro shipped over. It's been in a box for 7 months (original box, properly packaged). I bought a cheap arse $10 LCD monitor from Goodwill to get me through till Friday when my new monitor arrives - it's a vga connection which I've got plugged into one of the DP's through an adaptor - as I said, it seems to be working fine. I fired the box up on Monday no problems. Updated to El Capitan from Yosemite, did all the set up, updated whatever else I needed to. So far so good. Tuesday night, the box randomly turned itself off while I was working on Photoshop. Weird, but I restarted it fine. Wednesday morning - Box would not power on at all. I unplugged it, swore at it a lot, left it for 30 mins, came back, tried again - the box turned on BUT no monitor connection. Checked monitor with laptop, monitor fine. Unplugged, turned off etc etc, restarted box by holding down power button, tried to blindly reset the NVRAM (cmd/option/p/r), tried other monitor port, left it for 30 mins, came back, swore at it some more, turned it on and it all fired up fine. (monitor included) Tried to some diagnostics to see if there was an error - nothing came back. Wednesday night, box abruptly powered off again. Tried restarting, powered on but no monitor connection. Left it, unplugged it. Came back. Tried it. No good. Went to bed. Thursday morning - same as previous night: box powers on but no monitor. Friday morning: box won't power on. So is this a graphics card issue? Power issue? El Capitan issue? Bad Karma issue? Any help greatly appreciated. Box Details: Mac Pro mid-2012 (5.1) - Quad Core 3.2 Ghz. 20 GB ram ATI Radeon HD 5770 1GB Can't remember all the HDD's but I have 4 installed - all minimum 1 terrabyte. OS on dedicated HDD (Not SSD tho) El Capitan (just updated on Monday 13th June 2016 so it should be the latest) I do not have anything like MacCleaner or any of those programs running. Neither am I running any anti-virus software All the software (Adobe CC, MS Office etc) is legit. It's not partitioned or using anything like boot camp etc - completely Mac dedicated. Quick note re: box power - I originally fired up the box with the original apple powercable - Australian connection with US adapter. However, I went out that afternoon and grabbed a US jug plug power cable and have been using that since. I have an ACER monitor with DVI connection arriving today, so I was going to test it with that, but as mentioned, the box will no longer power on at all. I realise I'm probably going to have to take it somewhere, but any advice (forewarned is forearmed) is greatly appreciated. Thanks ***UPDATE***: 1 minute after I posted this, everything powered up fine (monitor included). Any suggestions on diagnostics to run while this puppy is running?