Re: Samsung Syncmaster 225BW
******* Samsung Syncmaster 225BW FIX after unsuccessful re-cap ********
Someone gave a Samsung Syncmaster 225BW a couple of weeks ago to work on. I am familiar with this site & saw that lots of other people had issues with this monitor related to caps. This monitor also had 1 second video, and then cut-out with solid blue LED.
The caps & voltages all looked OK, with no evident ripple on any of the rails. I decided to spend the $4.00 or so for the caps since the caps are probably near EOL anyways. The re-cap was NOT successful, but I honestly did not expect it to fix the problem. ( I am an Electronic Engineer btw...and quite familiar with the design of switching power supplies incorporating PWM).
Unfortunately, I do NOT have the schematic for the inverter board, but found & used the data sheet & eval board of the Full Bridge CCFL Controller for reference. I observed the failure mode of controller & noted the voltages. I have made a couple of minor modifications to the circuit to compensate for a (possible) marginal design using thru-hole parts. All of the CCFL turn-on reliably now. I will take a few more measurements, tweak the values, and then finalize the repair with SMT parts this weekend. If anyone has the schematic for the controller board, it would be helpful for me to scrutinize the design further. Note, I think this model uses a few different controllers depending upon board revision.....so this might not be applicable to your unit.
Kev
******* Samsung Syncmaster 225BW FIX after unsuccessful re-cap ********
Someone gave a Samsung Syncmaster 225BW a couple of weeks ago to work on. I am familiar with this site & saw that lots of other people had issues with this monitor related to caps. This monitor also had 1 second video, and then cut-out with solid blue LED.
The caps & voltages all looked OK, with no evident ripple on any of the rails. I decided to spend the $4.00 or so for the caps since the caps are probably near EOL anyways. The re-cap was NOT successful, but I honestly did not expect it to fix the problem. ( I am an Electronic Engineer btw...and quite familiar with the design of switching power supplies incorporating PWM).
Unfortunately, I do NOT have the schematic for the inverter board, but found & used the data sheet & eval board of the Full Bridge CCFL Controller for reference. I observed the failure mode of controller & noted the voltages. I have made a couple of minor modifications to the circuit to compensate for a (possible) marginal design using thru-hole parts. All of the CCFL turn-on reliably now. I will take a few more measurements, tweak the values, and then finalize the repair with SMT parts this weekend. If anyone has the schematic for the controller board, it would be helpful for me to scrutinize the design further. Note, I think this model uses a few different controllers depending upon board revision.....so this might not be applicable to your unit.
Kev
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