Here is my story of how I fixed a defective FujitsuSiemens SL3260 (26" LCD). The problem appeared to be the classic '2 seconds to black' phenomenon. The previous owner told me the monitor all of a sudden stopped working along with a strong smell of burnt plastic.
I expected having to do a recap and maybe checking/replacing the transformers, CCFL's or mosfets. The culprit turned out to be something completely different, though. After opening up the casing and removing the 2 boards (with took some effort I might add) the actual cause was not difficult to spot at all.
This board has 2 transformers to drive the backlights. On each transformer each of the 2 'hot' lines (the thick pink or blue wire) going to the CCFL's is connected to GND through a HV cap. Strange thing is, these don´t have the same value. C504 and C519 are 12 pF, but C503 and C517 didn't have any clear value marking on them. After desoldering they turned out to be 5 pF. All 4 are rated 3 kV. In all, on each transformer one of the hot lines has a 5 pF cap and the other a 12 pF cap. Which is weired, why aren't they the same?
Now, on the PSU/inverter board C519 had dramatically burned up, it looked just like the head of a used matchstick. No visible markings about the value and voltage, of course. No clue as to why it had failed this catastrophically either, as the secondary of both transformers showed an almost identical resistance. After sketching out this part of the circuitry, I concluded the 'matchstick' had to be identical to C504. Amazingly, after desoldering it still measured 11 pF, very near its supposed value...
Schematics or service manual were nowhere to be found on the usual websites. I couldn't find anything on this forum either about the usual value of these HV caps, but maybe I didn't search properly. So I used a few Samsung service manuals to study this part of the circuitry, and concluded the value should not be terribly important. I replaced both 12 pF ones with 5 pF 3 kV caps I cannibalized from an old Samsung inverter board. In addition, as some solder connections looked a bit dodgy, I resoldered every single through hole component on this board just to be safe.
After reassembly the monitor immediately came back to life. I have had it test running now for about a week without any problems. The monitor does not smell 'electrical' or run very hot. I'm pretty confident it will be fine.
Only after I had fixed this monitor, I noticed a bump in this old thread https://www.badcaps.net/forum/showthread.php?t=15413 It deals with a Vizio LP2626 monitor that has a nearly identical PSU/inverter board (two 12 pF and two 5 pF 3 kV caps in the output circuitry), which showed exactly the same symptoms (a burned 12 pF cap). Even the component numbers for the 4 caps are identical. Don't know how and why I missed this thread.
re-atari
I expected having to do a recap and maybe checking/replacing the transformers, CCFL's or mosfets. The culprit turned out to be something completely different, though. After opening up the casing and removing the 2 boards (with took some effort I might add) the actual cause was not difficult to spot at all.
This board has 2 transformers to drive the backlights. On each transformer each of the 2 'hot' lines (the thick pink or blue wire) going to the CCFL's is connected to GND through a HV cap. Strange thing is, these don´t have the same value. C504 and C519 are 12 pF, but C503 and C517 didn't have any clear value marking on them. After desoldering they turned out to be 5 pF. All 4 are rated 3 kV. In all, on each transformer one of the hot lines has a 5 pF cap and the other a 12 pF cap. Which is weired, why aren't they the same?
Now, on the PSU/inverter board C519 had dramatically burned up, it looked just like the head of a used matchstick. No visible markings about the value and voltage, of course. No clue as to why it had failed this catastrophically either, as the secondary of both transformers showed an almost identical resistance. After sketching out this part of the circuitry, I concluded the 'matchstick' had to be identical to C504. Amazingly, after desoldering it still measured 11 pF, very near its supposed value...
Schematics or service manual were nowhere to be found on the usual websites. I couldn't find anything on this forum either about the usual value of these HV caps, but maybe I didn't search properly. So I used a few Samsung service manuals to study this part of the circuitry, and concluded the value should not be terribly important. I replaced both 12 pF ones with 5 pF 3 kV caps I cannibalized from an old Samsung inverter board. In addition, as some solder connections looked a bit dodgy, I resoldered every single through hole component on this board just to be safe.
After reassembly the monitor immediately came back to life. I have had it test running now for about a week without any problems. The monitor does not smell 'electrical' or run very hot. I'm pretty confident it will be fine.
Only after I had fixed this monitor, I noticed a bump in this old thread https://www.badcaps.net/forum/showthread.php?t=15413 It deals with a Vizio LP2626 monitor that has a nearly identical PSU/inverter board (two 12 pF and two 5 pF 3 kV caps in the output circuitry), which showed exactly the same symptoms (a burned 12 pF cap). Even the component numbers for the 4 caps are identical. Don't know how and why I missed this thread.
re-atari