Why won't my Xbox 360 stay on?

Ok i got this Xbox 360 it's a 2005 model and seeing as it's old i'm guessing something gave up on it. But i'm still not too sure. I'm seeking some help.

Ok so the problem is that it turns On but then in less than a second it then shuts off. I can keep doing it and it just shuts off. So i dissambled it and tinkered around disconnecting the DVD drive and the RF module. I removed both. So i decided to instead turn on the Xbox via the Controller so it did turn On but it just turns On the fans. Nothing else is operating. USB ports aren't working. No Display. Nothing at all. So while it's on i connected the RF module and it just gives me a green light in the middle. No red ring lights. I am using component cables.

(this model has no HDMI port) Pressed Y + Right trigger to reset display nothing happens. What's weird about all i've seen is that with the

- RF module attached it will turn on less than a second.

- Without the RF module but this time with the controller i can turn it On.

- When it turn on only the fans work. Nothing else is On.

- Power brick is fine. I've tested it on a 2nd Xbox 360 (Living room)

This Xbox was reballed last year by a professinal electronic repair man. It worked before this happened and tempetures were low at 40c - 50c using AS5 paste and also it has no X-Clamp fix. It's using the original X-Clamps.

I don't know what's wrong with it. I'm just left clueless.

I mean .. I checked all the ports that might be causing a short. Nothing. I don't see anything at all nothing is bent or damaged. I don't think it's overheating or lose BGA or something about the CPU or GPU. The CPU and GPU are in fine condition. That's why i'm not getting any red ring lights.

Has anyone had something identical to what i have on this Xbox 360?

How can i fix it? I don't really want to have to send it again to a repair shop.

HOPEFully someone here knows whats up.

Yeah. Yeah. I know. You are probably thinking it's an old System. I should just give up on it and move on. But i really enjoy this Xbox. It's been with me since 2005, and its rarely used. I only play like for an hour or two either Skyrim or Oblivion. Maybe like 2 days each week.