White Screen ...got stuck booting,recovering,etc

Had a black screen with no signs of life.Replaced power supply which was not a problem.Replaced logic board, at the time of very first time powering a new logic board had a single beep every few seconds.Shutt the system down pulled RAM and reinserted back.Not sure if that helped at that time to start up a system but it did started somehow.It was up and running for a 30 min or so…after that the screen became sort of flickery and distorted.

Decided to restart the system and then got stuck on a white screen with the Apple logo and a progress bar .It does not get beyond 60% on a bar…Removed HDD and replaced with formatted one from another computer.Ceated a bootable install USB and that does not help…still the same. Created a bootable Memtest86 USB ,the test on RAM Pass no Errors! AHT signals no hardware problems. Tried SCM and PRAM reset and no go on a white screen with the Apple logo and the progress bar which gets little bit of tiny and short lines in it and a logo as it gets closer to 60% ……