IMac 24" doesn't start after installing Mavericks.

Question

After installing Mavericks (10.9.2) the machine started having hiccups... rebooting at random times on it's own.  After upgrading to 10.9.3, it only got worse.  Reboots were more frequent (as little as 1 minute between each reboot).  Then it took the final step and went into a state where it remains with black screen, the startup jingle may begin, but is killed within half a second or less... goes into a reboot loop.  The DVD sounds, then it tries to reboot again, DVD sounds... sometimes the jingle starts... but is cut off by a reboot.  Trying to get ANYTHING done with different key press combinations (option+command+R+P, D, T, Command, Option... pretty much every single combination one can find online for accessing safe boot or recovery or whatever... does not work.  The machine seems to have been killed by Mavericks.  I have come across a LOT of posts by other people who have experienced the same thing (rebooting after installing Mavericks) going back to October last year, and a few have experienced the same dead computer issue as I am having... all the while there is no fix or explanation from APPLE regarding this issue.  I have even opened the machine up and checked all cable connections, tested the HDD on another computer (was ok), cleaned the memory module connectors etc.  Before the total crash I had installed a temperature monitoring program with ventilator control, due to the DVD ventilator running at high RPM after installing Maverics.  All the temp sensors were reporting modest temps (ranging from 39 - 79 Celsius (only the power supply was above 50 Celsius). 
The computer is as useful as a brick by this point. Since it went dead, it has successfully started up 3 times (out of 500+ attempts), but rebooted within a couple of minutes, into it's cycle of dead reboots.
One way of getting it to boot and prepare for re-installation, is to keep the power button pressed until it sounds 3 times long, 3 times short and 3 times long beeps... it would only start making the first beep... then it rebooted in to death again.
Could it be that Mavericks is destroying the firmware, or even killing the hardware?  I also have Mavericks on MBA and MBP, where the MBA has no problems, while the MBP freezes up every 2 days or so... requiring a forced reboot.
Anyone with a usable advice on what to do in order to get the machine working again?  How many years does it normally take APPLE support staff to fix serious issues like this one?  It's already been over 7 months since the first people began experiencing these issues with Mavericks, but nothing has been done about it on APPLE's end ... as far as I can tell.
Looking forward to some solutions.

Answer 1

Just wanted to write the conclusion of this issue here, and make things as clear as possible.
I took the iMac to a support center, and they confirmed that several components on the power supply board were fried and other parts had been overheated.  It took a few weeks for them to get the needed parts (much cheaper than replacing the entire unit).  I brought the iMac back home and started it up, and it did work... but it was getting very hot very quickly. I was thinking that maybe I should install Mountain Lion on it, and get away from Mavericks... just in case.... the computer had been turned on for around 1 hour at that point, and then it rebooted.... and stayed dead for 10 minutes or so... until it could start up again.  Was on for a few minutes... then dead again.
Clearly the cause of the problem was still present, and fixing the symptom did not prove to be a lasting solution.
The machine would not stay turned on long enough (when it DID turn on) for even formatting the disk, so I removed the SDD from it, formatted it with my MBA (connected through USB), and inserted it in the iMac again.  Starting it up resulted in a few minutes being turned on, overheating and crashing. Having downloaded ML and created a USB installer for it, it was now a case of trying one's patience ... hoping for the machine to stay turned on long enough to make it all the way through the installation process.... it managed to do the first part of the installation after several hours of crashing and overheating.... and it came to a point where I simply turned it off and gave up... thinking that the problem simply was physical in nature, and not caused by Mavericks as I had assumed from the start.  Next day I had renewed energy, turned the puter on and it behaved in the same way... turning off, then starting by itself trying to get through the installation.... it would fail again and again... I left the house, with it turned on, hoping that it would at least manage to finish at some point in time... so that I could write off my "BAD Mavericks" suspicion.  When I returned several hours later, the installation was complete and the machine was purring quietly and the back of the computer was NOT hot like a steam iron.
Now it has been working for several days without any problems at all.
The final conclusion is this:
Mavericks IS at fault, and will physically DESTROY computers that are "somehow" not compatible with it.  I would have thought that Apple had enough capable engineers to prevent the operating system to mess up the hardware in this way, but clearly I was wrong on that account.  I can only WARN other people to even attempt installing Mavericks on puters of this type:
Hardware Overview:
  Model Name:   iMac
  Model Identifier:     iMac7,1
  Processor Name:       Intel Core 2 Duo
  Processor Speed:      2.4 GHz
  Number of Processors: 1
  Total Number of Cores:        2
  L2 Cache:     4 MB
  Memory:       4 GB
  Bus Speed:    800 MHz
  Boot ROM Version:     IM71.007A.B03
  SMC Version (system): 1.21f4
  Serial Number (system):       W8*******X89
  Hardware UUID:        00000000-0000-1000-8000-001B639688F7
Anyone claiming that Mavericks is not at fault, is plain and simple WRONG, in DENIAL or LYING.  There is absolutely NO doubt in my mind any longer, that the problem was indeed Mavericks getting installed on the machine and messing with the hardware on a level where it should never happen. If someone working at Apple would like to purchase/replace my iMac in order to test it and figure out that this is a REAL problem, they are welcome to do so. I think it is more than guaranteed that the damage caused by this Mavericks nightmare installation will never be recovered, nor will the time and work lost ever be compensated, but I would actually like Apple to acknowledge their responsibility and failure to address this issue in a professional and responsible way.
IF Mavericks was NOT at fault, then someone should explain the logic behind the machine physically burning components shortly after the installation of Mavericks, and even when the SDD had been wiped clean with no OS, it was still overheating and shutting off, until it could finally have ML installed... and at that point it was cured and has worked flawlessly ever since.  Not a single hiccup, no over heating, no problems.
My offer to sell/replace the iMac stands if Apple is really interested in looking at this SERIOUS issue with Mavericks.  This is NOT a minor issue they should expect simply goes away, or will be ignored by people who experience their machines BURNING to pieces.
On my MBA and MBP Mavericks is not causing any problems, so it is not "all bad", but for the iMac it meant total annihilation.
Anyone who has installed Mavericks on their iMac of similar age as mine, having rebooting and overheating problems: REMOVE the Mavericks installation ASAP and get ML on it before it goes up in flames!
Other Mac's have been reported having the rebooting/overheating problems as well, although I have not noted down which builds those were.  The problem is REAL and COSTLY for those who experience it.... both time-wise and in terms of lost time/work.
Hopefully this will help others from getting the same terrible experience as I got, and save some computers from burning up.
<Personal Information Edited by Host>