MY IMAC 20011 DESK TOP WENT BLANK I WAS TOLD IT WAS CAUSED BY CIGERRET SMOKE AND NICATEEN BUILD UP HOW CAN I FIXS THIS ?

As an ex-Apple employee who repaired those models, I would be suspect of such claims. Reality is, all things fail. Just the sad truth. Whilst being employed, I did run into a few machines that we were able to refuse service due to the degree of "TAR" that we encountered upon the diagnostic stages. I am mean, this stuff was thick! Could something like this damage components? Sure, but it would be hard to conclude. Though if thick enough, it would be well reasonable to state that the onus is on the owner.

With regards to fixing it... it really depends on what specifically is wrong. The display is a swap out unit. Not difficult to do, though Care needs to be taken when pulling it off*** The video Card could be out, resulting in similar behavior... or even something on the MLB (Main Logic Board) or Mother board to most people.

Test! Plug in an external Display. Does it work? if so, then 90% chance it is the internal display that is bad, not the video card or MLB. if not... then... well... you have a lot more investigation to go through. if it is the display... replace it... you can probably get the parts off of eBay or iFixit.com (iFixit.com will probably include instructions, they are good that way)

Very Crude How-To
*** it is easy to tear out cables, which would be more damaging than just the display issue. You will need a set of suction cups (at least that is the easy way) to remove the front Glass. Magnets hold the glass to the Frame (it is true, newer ones just use Double stick tape). and either a T-8 or a T-10 (I don't specially recall) to remove the Display from the Main Housing. (the Torx screws are along the edges) Once that is done, Lay the Mac on it's back (Display up) from the bottom... SLOWLY!!!! Lift (Tilt) the display up Did I say SLOWLY! the cable that attach to the display are very short! NOTE: where these short cables go, as you disconnect stuff. including the camera cable at the top as on some models the routing is funny. The display cable is the long one, but it is taped to the back of the display with a Dark Brown tape. Do your best to not wreck that tape, unless you have more (iFixit.com might provide it... not sure)

Another option... and, unless your exceptionally inclined Just plug-in the external monitor (if it works) and use it as such. Granted, not what I would do, but it would be easy.

For both of your sakes, QUIT SMOKING... I find it hard to believe that you could have that much build up and not be dead. If that's the case you need to dissassemble the machine and clean it out. I know of no other fix, if the problem is what you state. As a suggestion, search on google (or whatever search engine you use) for how to boot into diagnostics or some other mode.

Usually holding the command and other keys will allow this. That should at least give you some idea of how much damage has been done.

Not to pick on you, but I find it hard to believe that anyone would smoke when we KNOW the damage it causes. Might as well shoot yourself (and your ocmputer) in the head! Please stop smoking.

Sorry about the editroial, but I have the info I've give you helps you sort out the problem with your machine.

Jack

P.S. Quit shouting (Get out of CAPS lock!!!!)

Nice one but no, sure power plug is in the rear, it happens, gently wiggle may solve.

If not try holding on/off switch in a little longer than normal