Philips 42PF7320

Hi I have had four of these sets in my workshop, all with the same fault. The picture and sound disappears but the green LED stays green (no red flashing error codes). If you turn the set off then on again it comes right untill it does this again, very intermittent. There is also no error codes in the software. I was advised by Philips tech support to replace the NVM IC on the SSB board, I did and this did not fix the fault. I then decided to replace the PSU board, this seemed to have fixed the fault, sets ran for three weeks non stop ok. Sent back sets to customers. One customer has said their set faulted again. Has anyone came across this fault before. Could it be a slight voltage problem eg VS or VA voltages from the power supply.