Samsumg 42pspf301501a no power main input ok

Your power board voltages are ok. I'd look at a main board issue. You could try "cooking" the main but even if it fixes it it's a temp fix

Mostly is the back lights strips, you may use a led check to check it out.

1. Make sure the back lights are OK, to do so, unplug the cable between the power supply & the main board, apply the AC power to the power supply, if the back lights are OK, it should light up.
2. If the back lights are OK, i will try a new main board first.

Fault at its main digital board. Short circuited component/s at it. Contact any service technician; or the authorized service center. If you wish to get some details; check the site linked here. Surf the site with patience. Pull up older posts.
http://electronicshelponline.blogspot.com/
In most cases, the main board might have to be replaced. If so, a software [firmware] update too might be necessary.

Remove Mains Plug and press Standby switch from LED Panel for 30 sec.
Press Input & Ch Down Switch from LED panel and plug in and start LED
LED will start and "K" will appear on screen
Press Ch Down & Vol Down switch at same time
You will get 1/10 page on screen
Go to 9/10 page by pressing left & right button from remote
Select EEP and press Ok button from remote
After 30Sec remove main plug and restart LED.

Fault with the main power supply regulator board. Check and replace damaged component/s at its main power regulator [SMPS] section circuit. Contact any service technician. If you wish to get some details; check the site linked here. Surf the site with patience. Pull up older posts.
http://electronicshelponline.blogspot.com/
Check its ON/OFF switch too for any contact failure. Replace it before do any other repair work.

ok, when you plug in the set, does the power light come on? Assuming you ordered a power supply in good working order, you may very well have a faulty main board. The power supply produces standby power that the main board uses to power the standby/power on light. Your main board also uses the standby power to provide the "ON" signal to turn on the rest of the power supply.

Does it have a standby light? If standby light is visible main fuse is likely ok, Suspect bad power supply check capacitors for swelling on the power board, if not, suspect main board.

hi,
There is a standby transformer inside the Onkyo receiver at the mains input stage. If the standby transformer is faulty then the unit will not power on. There will be two transformers. One is big and the other is a small one. The small tarnsformer is the standby transformer. Which will be fitted on a small board where the power cable is connected. Replace the transformer to rectify this problem.
OK

hi,
check the power cable first. also the power at the wall out lets.
if ok the you have to check the input ac fuse of your receiver. your recever has problem with its power supply stage, that's why there is no standby light also. fist of all check the fuse. then check the standby transformer is it faulty or not. the system will power up if the standby transformer is ok. standby transformer is a small transformer near the mains transformer. check these things first, if u need any further assistance feel free to contact me through fixya.
ok