I felt it was time to post another case history.
Gateway 2100 LCD monitor, the monitor would turn on screen would flicker and then go black. After opening the monitor I found 1 capacitor, 47
uF @16V with an
ESR of 10 ohms(obviously bad) in the secondary side of the
SMPS section of the
SMPS/Inverter board. Looking at the inverter section I noticed two puffed and vented electrolytic capacitors both 220
uF @16V, locations C301 and C302 that were obviously bad as well. Sorry but I did not record the location of the 47
uF capacitor, but you can see where all the capacitors were located in the photos. I also noticed some darkened spots on the component side of the PCB, on the other side, the solder side of the PCB you could see that
where the dark spots were is where the inverter circuit
MOSFETs were located, U301, U302, U304 and U305.After testing the
MOSFETs for shorts between gate to drain and gate to source to my surprise they tested good, but they did have major solder connection problems, the solder on their connections had completely broken down from heat. I re-soldered all the connections and replaced all the bad electrolytic capacitors and checked for any other problems with the monitor. After putting the monitor back together hooking up
signal and turning it on, it worked like new.
If you are wondering why the transistors are identified with a U instead of a Q, as normally transistors are labeled with a Q and
ICs are labeled with a U, well this is the case on some
PCBs the designers will label transistor locations with U instead of Q and instead of labeling
ICs as U they will just print
IC.
Mail in repair service:
We offer mail in repair service on LCD monitors. We do the repair on the PSU/inverter board from the monitor in this post for $75.00 plus return shipping and handling.
Click here to see our
mail in repair service page for more information.
