Viewsonic VA1903WB no stand-by power

[PinGuy]

Hi all, I am diagnosing this old monitor that died on me while off but plugged in.
The standby light won't turn on at all.
With the mainboard disconnected, the power supply shows both 12V and 5V but they both fluctuate (12V is fluctuating between 9-13V and 5V is fluctuating between 4.5-5.4V). A tiny click-click sound is heard every second.
All capacitors are visually intact, and I measured them all with their capacity and ESR in the correct range.
I don't think this is a problem in the 5V or 12V but a problem in the HV section that makes the power supply restart continuously.
Any tips on how to diagnose where the short is in this HV section?
Attached pictures of the boards.
TIA

[PinGuy]

Re: Viewsonic VA1903WB no stand-by power

After removing the jumpers that power the HV section entirely, the clicking is still there. The 12V is at 14V, and the 5V continually floats between 4.9-5.4V, I noticed the click occurs when it reaches 5.4V as if the overvoltage is detected and the protection trips, then once it lowers to 4.9V it powers again and repeats, all this in less than 1 second. I measured everything on the secondary as well as on the primary, no shorts at all. Could it be a bad LD7575 that is acting up and overdriving the PS?

[PinGuy]

Re: Viewsonic VA1903WB no stand-by power

Ok, problem solved!
After some more checks (removing the transformer and injecting external 12V and 5V to find there were no shorts anywhere on the secondary), I found the culprit was the TL431 for the feedback to the primary. Never seen one of these fail, but you know, there's always a first time for everything!

[HellasTechn1]

Re: Viewsonic VA1903WB no stand-by power

Never seen one of these fail, but you know, there's always a first time for everything!

Me neither and yes surely there is a first time for everything !