HELP! My Mac Pro 2012 won't turn on!!

SOLVED!!! First, many thanks to everyone who posted help! I managed to solve the problem using a technique I used many times on PCs: 1) Unplugged the Power Supply from the board. 2) I removed the battery; graphics card; DVD reader; and unplugged the power cord from the Power Source. 3) I pressed the on/off button for 2 minutes to remove all energy load from the components. I waited approximately 40 minutes. 4) I plugged the power cord into the Mac Pro without putting the battery, graphics card, DVD player or SSD/HDD Disc. The instant I reconnected the power cable, the Mac turned on and did the "BONG" Then I quickly turned on the keyboard and did a RESET PRAM by the keyboard. Afraid of turning off the power, I turned on the graphics card with the Mac On. I know it's not correct, but where I live, technical assistance is no longer paid for being discontinued. Anyway, I put the graphics card with the Mac turned on and it gave video and I put a pendrive with the ASD (Apple System Diagnostics). and everything OK!!!

Dear Grant, I still have the same problem. I'm very sad! I left the Mac Pro on until yesterday, when I decided to turn it off before going to sleep, but I left it on (Nobreack). Today when I went to turn on the on/off button on the Mac Pro, the same problem happened: It quickly turned on the front LED and turned off, it didn't start. So I did all that procedure, I unplugged the power cord, waited 15 seconds, plugged in the power cord again and waited 5 seconds, but it didn't start. I tried this procedure three more times without success! So I decided to do as the last time it worked, plug in the power cord and press the on/off button several times, until after about 20 minutes of doing this it took off. Before, I even tried the hair dryer near the power source, because when I had PCs and a similar problem happened, I only needed to heat the power source a little and it worked. But it didn't work with the Mac Pro, which makes me think it's not a problem with the font. After it turned on I turned it off to reset the HDD/SSD, and then it turned on perfectly. So I did the AHT and this time detected an error: 4MEM/62/40000000: 0x7a6efd98, but this error did not appear the other times the problem happened. looks like a memory error. So I did the ASD and found no PASSED error. So I decided to do a test: I removed the CPU tray and tried to turn it on, but it didn't boot. I put the tray back and he called. I remember you said that without the tray it should start and keep the fans running. But without the tray, it doesn't really boot. Remembering that after it gets to boot, I turn it on and off perfectly. He just doesn't call when I hang up for a few hours. In other words, it's like draining the power of some component when it spends a few hours turned off. And once it gets started, if I turn it off and on within an hour, it works. What do you think it might be?

I already replaced the 3V battery with a new one. And nothing has changed. I press the Power button, and the Mac won't start. I am desperate!!! I bought this Mac in November 2013 at the official store, new. And I'm very careful. super new! Is it the Power Supply? Though it turns red when I plug it in.

Hi guys! I need help! the computer worked normally, turning on for 5 days. However, after 2 days without turning it on, yesterday when I went to call it didn't start! It made a quick noise as if it had tried to start, but it didn't turn on. So I redid everything I had done to work last week: (unplugged the power cable from the backplane; removed the CPU flag; removed the GPU; CMOS battery, and pressed the power button for 4 minutes. then waited more than one hour). Then I reconnected the power supply cable to the back plate; I put the CPU flag again; GPU, and plugged in the power cord, waited 5 seconds and pressed the power button, but it didn't work. So I turned it off again, and left the rest of the night off and went to sleep; after 6 hours I tried turning everything on again but it didn't work. So I turned off and on only the CPU flag with only one stick of memory in the first slot, ah... and without the CMOS battery. enjoying the Power button and he turned it on until it made the "BONG" sound, but turned it off by itself suddenly. I tried to redo the same thing, but it didn't take off anymore. The DIAG LED when I press it turns yellow 5v light. In other words, theoretically the power supply and the logic board are in good condition. But I have seen some posts from other users with an obsessive problem, and they only had success when changing the back plate for another one. 😢 But how could it have worked for a week. And I always hung up at the end of the day and turned on normally the next day. However, after TWO days without me turning it on, it goes back to the problem. When I used a PC, and something like that happened, it was usually the source, and I just turned on the nearby hair dryer to heat it up, and it worked. PLEASE!!! SOMEBODY HELP ME! Here in Brazil, I don't have technical support for this machine. And I'm desperate, because I survive the music production work with this computer. HELP!!!

Hi guys! I need help! the computer worked normally, turning on for 5 days. However, after 2 days without turning it on, yesterday when I went to call it didn't start! It made a quick noise as if it had tried to start, but it didn't turn on. So I redid everything I had done to work last week: (unplugged the power cable from the backplane; removed the CPU flag; removed the GPU; CMOS battery, and pressed the power button for 4 minutes. then waited more than one hour). Then I reconnected the power supply cable to the back plate; I put the CPU flag again; GPU, and plugged in the power cord, waited 5 seconds and pressed the power button, but it didn't work. So I turned it off again, and left the rest of the night off and went to sleep; after 6 hours I tried turning everything on again but it didn't work. So I turned off and on only the CPU flag with only one stick of memory in the first slot, ah... and without the CMOS battery. enjoying the Power button and he turned it on until it made the "BONG" sound, but turned it off by itself suddenly. I tried to redo the same thing, but it didn't take off anymore. The DIAG LED when I press it turns yellow 5v light. In other words, theoretically the power supply and the logic board are in good condition. But I have seen some posts from other users with an obsessive problem, and they only had success when changing the back plate for another one. 😢 But how could it have worked for a week. And I always hung up at the end of the day and turned on normally the next day. However, after TWO days without me turning it on, it goes back to the problem. When I used a PC, and something like that happened, it was usually the source, and I just turned on the nearby hair dryer to heat it up, and it worked. PLEASE!!! SOMEBODY HELP ME! Here in Brazil, I don't have technical support for this machine. And I'm desperate, because I survive the music production work with this computer. HELP!!!

Grant Bennet-Alder, the fans don't spin either. the only thing that lights up is the red light that flashes when I plug in the power.

I took everything away. But it doesn't beep when I turn on the Power button.

Any idea? Please!!!

Any idea? Please!!!

SOLVED