ACER XB27 , shorted tcon, bad caps?

[danishaznita]

Good day all ,

I have a ACER XB27 that go onto only to white screen .

Upon disaasembly, a Transistor at Q308 is burned good, and two big ceramic caps beside it is blacken . I removed both component , and checked for short (between Fuse and ground) and get 37 ohm, which is still too low .


After weeks of digging old posts about Tcon , i stumble upon this old post from 2017 (https://www.badcaps.net/forum/showpo...0&postcount=19), which user momaka wrote

" first measuring the resistance from each of those test points above to ground. Anything with less than 100 Ohms resistance indicates a possible short-circuit, and anything with less than 50 Ohms (especially VDD, VGH, and VGL) is quite likely to be a shorted or partially-shorted ceramic cap"

So i went back to my board, probed every testpoint and only 12V-IN returned 37 ohm . Then , i went ahead and probed every single ceramic caps that are still attached to the 12V power plane and all of them returned 37 ohm.

I am at lost now in tracking what component is shorted. Your guidance is much appreciated.


Note : i am a student and only own a multimeter and a solder . so voltage injection is out of question


Pictures : https://imgur.com/a/ZiCXrzo

[CapLeaker]

Re: ACER XB27 , shorted tcon, bad caps?

Momaka is correct what he said. It may indicate a shorted ceramic cap. Also a shorted MLCC cap reacts to heat and the resistance will change. So you could heat (heat gun / wifeys hair dryer, soldering iron) and freeze (can of air upside down) each suspected MLCC. Not having a bench PSU available sucks, basically you have not much possibilities left, besides reinstalling that board and see if the voltage comes back up, or section that affected circuit up by either cutting traces or taking strategically components out trying to isolate where the short comes from. The best and laziest way to tackle this is with voltage injection and 99% IPA or a thermal camera.