Hardware PS3 Slim Red blinking light on cold boot only?

[Stremon]

Hi guys,

I recently got a PS3 Slim (120Go cech-2000a) in very good state for cheap ($15) because it seems to be faulty.
The problem it has is that on cold boot, and cold boot only, around 60% of the times, it switches on 2 second, beeps 3 times and shut down with a red blinking light, which usually means a system failure. If I reboot it right away, after 1 or 2 attempts it boots correctly and I can play hours without any issue, with real disc games or PSN games

After installing a 4.82CFW, I check the temps, which seemed normal (around 60°C in Multiman and 70°C after few hours of gaming).
I also opened up the ps3 to clean the fan system and secure the cables, which didn't change much.

Does any of you guys have an idea of what's happening here? it sure doesn't seem like a overheating problem, so from what other component could it be coming?
I know some people will say it a sign of an incoming YLOD, but if it was the case would it still be working for hours after booting fine, and would it stay cool?

Edit: I forgot to mention few things:
I have no yellow light at all before the red lights, only red.
And it happens only on cold boot, once the system in powered on correctly then switch it off, and if I don't leave it off too long it's always powering on without any issue.
So after those tests I suspect it to be a AC power Bloc issue (or maybe a blueray drive PCB problem but less likely), but before buying a replacement part, I wanted to ask if anyone had the same issue already or some knowledge on it.

 

[Ryccardo]

Yes, flashing red can be caused by power problem (easy way to cause it: use a mechanical power switch, turn it off and quickly back on while the console is running); I would guess capacitors on the output side of the power brick are aged, and can't keep the voltage stable enough at high loads