2nd Display not working on iMAC

          I have a 2nd display that has recently stopped working with my iMAC - I had issues with the second monitor before I upgraded to 10.9 - then the problems went away ... had a bad storm one night and power flickered on / off.  And can't get it to work since.  I know the monitor / cord is good because i have an Mac Air and I plug it in and it comes right up and works great.  I cleared the system log - unplugged and replugged the monitor in.. i don't see any errors in the system log..  can anyone see what is wrong? I cleared the log and put a marker on each side of the output.. I looks to me to see it - it say display added then right after that display removed..
4/11/14 10:19:24.832 AM Console[11817]:  Marker - Apr 11, 2014, 10:19:24 AM
4/11/14 10:19:27.809 AM WindowServer[96]: Received display connect changed for display 0x42c0140
4/11/14 10:19:27.814 AM WindowServer[96]: Found 60 modes for display 0x042c0140 [39, 21]
4/11/14 10:19:27.835 AM WindowServer[96]: Received display connect changed for display 0x3f003d
4/11/14 10:19:27.835 AM WindowServer[96]: Found 1 modes for display 0x003f003d [1, 0]
4/11/14 10:19:27.836 AM WindowServer[96]: Received display connect changed for display 0x3f003e
4/11/14 10:19:27.836 AM WindowServer[96]: Found 1 modes for display 0x003f003e [1, 0]
4/11/14 10:19:27.849 AM WindowServer[96]: Display 0x042c0140: GL mask 0x1; bounds (0, 0)[2560 x 1440], 60 modes available
Main, Active, on-line, enabled, built-in, boot, OpenGL-accel, Vendor 610, Model b005, S/N 0, Unit 0, Rotation 0
UUID 0x1cbf8fef38ae9dfec93508341d780c47, ColorProfile { 2, "iMac"}
4/11/14 10:19:27.849 AM WindowServer[96]: GLCompositor: GL renderer id 0x01022724, GL mask 0x0000000f, accelerator 0x0000449b, unit 0, caps QEX|MIPMAP, vram 1024 MB
texture max 16384, viewport max {16384, 16384}, extensions FPRG|NPOT|GLSL|FLOAT
4/11/14 10:19:27.849 AM WindowServer[96]: Display 0x003f003f: GL mask 0x8; bounds (3584, 0)[1 x 1], 2 modes available
off-line, enabled, OpenGL-accel, Vendor ffffffff, Model ffffffff, S/N ffffffff, Unit 3, Rotation 0
UUID 0xffffffffffffffffffffffffffffffff
4/11/14 10:19:27.849 AM WindowServer[96]: GLCompositor: GL renderer id 0x01022724, GL mask 0x0000000f, accelerator 0x0000449b, unit 0, caps QEX|MIPMAP, vram 1024 MB
texture max 16384, viewport max {16384, 16384}, extensions FPRG|NPOT|GLSL|FLOAT
4/11/14 10:19:27.849 AM WindowServer[96]: Display 0x003f003e: GL mask 0x4; bounds (3585, 0)[1 x 1], 1 modes available
off-line, enabled, Vendor ffffffff, Model ffffffff, S/N ffffffff, Unit 2, Rotation 0
UUID 0xffffffffffffffffffffffffffffffff
4/11/14 10:19:27.850 AM WindowServer[96]: Display 0x003f003d: GL mask 0x2; bounds (3586, 0)[1 x 1], 1 modes available
off-line, enabled, Vendor ffffffff, Model ffffffff, S/N ffffffff, Unit 1, Rotation 0
UUID 0xffffffffffffffffffffffffffffffff
4/11/14 10:19:27.869 AM WindowServer[96]: Display 0x042c0140: Unit 0: Startup Mode 2560 x 1440, CGSThirtytwoBitColor, Resolution 1, ioModeID 0x80000000, ioModeDepth 0x2, IOReturn 0x0
4/11/14 10:19:27.869 AM WindowServer[96]: Display added
4/11/14 10:19:27.869 AM WindowServer[96]: Display removed
4/11/14 10:19:27.870 AM WindowServer[96]: Display 0x042c0140: GL mask 0x1; bounds (0, 0)[2560 x 1440], 60 modes available
Main, Active, on-line, enabled, built-in, boot, OpenGL-accel, Vendor 610, Model b005, S/N 0, Unit 0, Rotation 0
UUID 0x1cbf8fef38ae9dfec93508341d780c47, ColorProfile { 2, "iMac"}
4/11/14 10:19:27.870 AM WindowServer[96]: GLCompositor: GL renderer id 0x01022724, GL mask 0x0000000f, accelerator 0x0000449b, unit 0, caps QEX|MIPMAP, vram 1024 MB
texture max 16384, viewport max {16384, 16384}, extensions FPRG|NPOT|GLSL|FLOAT
4/11/14 10:19:27.870 AM WindowServer[96]: Display 0x003f003f: GL mask 0x8; bounds (3584, 0)[1 x 1], 2 modes available
off-line, enabled, OpenGL-accel, Vendor ffffffff, Model ffffffff, S/N ffffffff, Unit 3, Rotation 0
UUID 0xffffffffffffffffffffffffffffffff
4/11/14 10:19:27.870 AM WindowServer[96]: GLCompositor: GL renderer id 0x01022724, GL mask 0x0000000f, accelerator 0x0000449b, unit 0, caps QEX|MIPMAP, vram 1024 MB
texture max 16384, viewport max {16384, 16384}, extensions FPRG|NPOT|GLSL|FLOAT
4/11/14 10:19:27.870 AM WindowServer[96]: Display 0x003f003e: GL mask 0x4; bounds (3585, 0)[1 x 1], 1 modes available
off-line, enabled, Vendor ffffffff, Model ffffffff, S/N ffffffff, Unit 2, Rotation 0
UUID 0xffffffffffffffffffffffffffffffff
4/11/14 10:19:27.870 AM WindowServer[96]: Display 0x003f003d: GL mask 0x2; bounds (3586, 0)[1 x 1], 1 modes available
off-line, enabled, Vendor ffffffff, Model ffffffff, S/N ffffffff, Unit 1, Rotation 0
UUID 0xffffffffffffffffffffffffffffffff
4/11/14 10:19:27.899 AM WindowServer[96]: MPAccessSurfaceForDisplayDevice: Set up page flip mode on display 0x042c0140 device: 0x7fccf9d04630  isBackBuffered: 1 numComp: 3 numDisp: 3
4/11/14 10:19:29.836 AM WindowServer[96]: **DMPROXY** (2) Found `/System/Library/CoreServices/DMProxy'.
4/11/14 10:19:29.868 AM WindowServer[96]: **DMPROXY** (2) Found `/System/Library/CoreServices/DMProxy'.
4/11/14 10:19:29.881 AM WindowServer[96]: Display 0x042c0140: Unit 0; ColorProfile { 2, "iMac"}; TransferFormula (1.000000, 1.000000, 1.000000)
4/11/14 10:19:29.893 AM WindowServer[96]: Display 0x042c0140: Unit 0; ColorProfile { 2, "iMac"}; TransferFormula (1.000000, 1.000000, 1.000000)
4/11/14 10:19:29.907 AM WindowServer[96]: Display 0x042c0140: Unit 0; ColorProfile { 2, "iMac"}; TransferFormula (1.000000, 1.000000, 1.000000)
4/11/14 10:19:29.934 AM WindowServer[96]: Display 0x042c0140: Unit 0; ColorProfile { 2, "iMac"}; TransferFormula (1.000000, 1.000000, 1.000000)
4/11/14 10:19:38.781 AM Console[11817]:  Marker - Apr 11, 2014, 10:19:38 AM

You can attempt to use Apple Hardware Test, if you do run it in Extended Mode 2-3 times. It's not the most reliable test however if it does locate an error that confirms you have a hardware fault that needs to be fixed. The ONLY alternative is to take it in for service. However IMHO I'd take it in to an Apple Store or AASP anyway, because A) AHT is not that reliable and B) even if it does find something that means you have to take it in.

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