I suspected the integrated TNY278 that I tried to replace with a new one but after replacing the component the defect persists.
The voltage on the green wire at the source output does not exist.
The voltage over the electrolytic capacitor of primary after the rectifying bridge is around 175V (B+) or so.
I tried to find the schematic diagram but couldn't

seems it is simply forward PSU with one high voltage mosfet like 2SK2654. (8-9 Amper 900-1100 Volt)
http://images.100y.com.tw/pdf_file/2SK2654.pdf
PWM regulated by something like UC3843.
https://www.elektroda.pl/rtvforum/topic2909875.html
http://deleted.vlab.su/view3/9420909/ade3263 ... 2fe9/1200/
Sunny Model ATX-250W
check all small elektrolitic capacitors around TNY

my question is , is it normal for the voltage on pins 2 and 4 of TNY278 to be almost equal around 165 v?

for 4 normal for 2 nonnormal

Мда у них еще и стандарты под 110 вольт

да не, судя по картинке, туда половинка выпрямленного поступает

This power supply uses a voltage switch. At the entrance after the rectifying bridge is used 2 200v electrolytic capacitors

comon sistem, discussion is about what entrance voltage You have: ~110 or ~230
I think half of rectified ~230V come to 4 pin of UC3843
rectified ~230 is about 324V, and half of it is 162V
rectiefied ~110 is 155V


PS. You wrote in english, so look like You are from US (where is popular ~110V), but Your nikname "eletmoraes" look liks more to spanish or romanesc (latin) language countries where ~230V dominated.