I had exactly the same problem, it happened after shipped the ps4 and didn't package it very well. Then after 20-30 min of gaming PS4 was loosing conection with HDMI and the light was white. Then i search the web what is the problem, i follow bobby's advice, i turned PS4 upside down and i put something heavy on the power supply. PS4 worked with no problem for 5 hours, when i turned the PS4 to its normal position the problem appeared again. I thought it was power supply and i bought other power supply and problem was still there. If it is not the power supply why when i put something heavy PS4 works? what part of PS4 The heavy item pushes and make it work? I heared about reballing the APU but this does not make sense in my problem. If the APU needs reballing no heavy item could make the PS4 work. So i dissaseble it and i saw that under the power supply is a metal plate and under this the APU, so the heavy item pushes the metal plate to touch APU. Between this two parts (APU, metal plate) is the thermal paste and thermal pads. So i thought thermal paste detached from APU and lost its abillity to cool. Do not underestimate the abillities of thermal paste, i put new thermal paste and now PS4 works fine for two days, PS4 hasn't turned off yet.