Mac does not start after crash

Thanks for your reply arbaman. I replaced the graphic chip already once. I also thought that could be the problem but if so, isn't strange that the hardware test didn't notice that and showed there no problems were found? Do you think that is convenient to replace the graphic chip and keep the mac as a backup buying a new one or is more conviene to sell it for parts? I don't think I'll go for the new mac for the impossibility to change its components.

Thanks again

Would be curious to know how long it lasted the replacement. Fact that AHT didn't pick the graphic chip failure is not so unusual, test is based on a number of values received by the various sensing components..it's an advanced check but not as advanced as one might think..many faults can slip through it. You're into a dilemma shared by many and I don't have a ready answer..there are pros and cons in any decision you might take. It also depends on what you use your computer for. Value of such machine for parts can be easily seen on ebay which has offerings of them every day..it's not that much and fixing would make sense. Only thing I can remark again..make sure if you go for it find someone reliable out there..I've seen many boards for parts with the original underfill still in place but browned by heat. Wonder how many have just reheated the chip for their customer hoping the "fix" would last longer than the warranty.