View Single Post
Old 01-24-2018, 01:04 PM   #1
Badcaps Veteran
Behemot's Avatar
Join Date: Dec 2009
City & State: Prague, 504'52.22"N, 1423'30.45"E
My Country: CZ
Line Voltage: 230 V/50 Hz
I'm a: Knowledge Seeker
Posts: 4,460
Default Acer B326HUL power supply dead

Display only blinks and than stays dead. Check open the PSU revealed it is dead.

There are three output rails: winding to feed the TEA1791T synchronnous rectification controller (this thing has no connection with primary side!), the output for the rectification transistor - this rail feeds the signal board, and than backlight rail.

Seems like the unit only pumps few cycles to the secondary so voltage rises a bit and than falls down as the caps discharge. I have about 15.5 V on a small cap on the primary auxiliary rail just after the diode which slowly falls, pumps again to 15.5 V and that repeats.

There is however oscillating voltage between like 18 and 19.6 V on the cap directly in front of the primary common PFC/PWM controller. Do not think this is normal condition. Cannot identify the controller right now, it has layer of lackquer, gonna have to try removing it.

I do see only 320V on the input cap though, there is no spike suggesting the PFC would be turning on, so maybe the problem lays in here?
Less jewellery, more gold into electrotech industry! Half of the computer problems is caused by bad contacts

Exclusive caps, meters and more!
Hardware Insights - power supply reviews and more!
Behemot is offline   Reply With Quote