| Electronics > Repair |
| bad caps on samsung lcd display |
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| P90:
I just fixed an LG monitor that had 3 bad CapXon caps. $3 and up and running again! woohooo! :) |
| Bud:
--- Quote from: linux-works on July 03, 2014, 03:29:28 pm --- it seems this model (Samsung 225BW) is nothing BUT trouble; --- End quote --- Hmmm.... The one I am using typing this message is I think 7 years old, still working fine |
| PlaneSailing:
Hello, looking for advice fixing my (nice when working) 2007 Samsung SyncMaster 226bw. Problem is after power on, top left screen shows the digital then analog box for a couple of seconds, then nothing, same issue after pressing the source button. Shining a strong flashlight at the screen, the "check signal cable" box can be seen moving about the screen, so looks like the backlight power supply (or control of it) has failed ?, but the backlights themselves are probably OK ?. Inside C113, a 330uF 25V SamWHA ? brand was bulging, replaced it with a 0.15 Ohm ESR new capacitor - the same problem. Replaced all 5 820uF with new 0.1 Ohm ESR Panasonic caps - the same problem. Replaced the 3 smaller capacitors (47uf, 22uf and 2.2uF) with no luck. Using a scope and 10" of wire soldered to the "13.5V" pins on the power connector showed a steady 15.6V with 100mV of 200kHz switching signal - not too unexpected. The ON/OFF line on the power connector is 0V when the monitor if off, and a steady 2.5V when on. The A-DIM and B-DIM lines are both about 0V with 50mV of noise, a bit less noise when the backlight is off. Seems a bit strange..... but it's the same when the backlight is on or off. I'm at a loss - maybe something has gone wrong on the high voltage side of the power board ?, appreciate advice, maybe retry with new capacitors ?, or I just buy a new (old but "working") power board on eBay ?, thanks. |
| wraper:
^With such problem - bad capacitors (most likely), bad ccfl transformer (measure secondary winding(s) resistance), or bad backlight lamp. |
| PlaneSailing:
Thanks wrapper for your reply. I have replaced all of the electrolytics on the power board with new low ESR caps. The backlight works for 2 seconds after power on and also works for 2 seconds after pressing the "source" button, so I "think" the capacitors, transformer and backlight lamp are OK ?. Appreciate if anyone has seen this symptom before or has idea, thanks. |
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