This Samsung 172T powers up fine, and looks normal for about 1-2 minutes. Then, it blinks off for a few seconds, then comes back on again. As it continues to operate, it spends more and more time off, and eventually only comes on for a few seconds.
It makes no unusual sounds and, when it is operating, the display is perfect, has normal brightness, and does not flicker.
I have swapped out both the power cable and the cable between the monitor and the computer. Neither change stopped the problem.
This behavior started several months ago, and when it first started, the monitor would blink off for about one second, but only every 5-10 minutes. Thus, it was annoying, but the monitor could still be used. However, the problem slowly got progressively worse, and the monitor is now useless.
After reading several hundred posts in this forum (and elsewhere) I replaced ALL the electrolytic caps (Capxon caps) with 105 degree, low ESR caps (from Digikey, mostly Panasonics). I did not skip any caps. None of the caps were bulging, and when I tested them all after removing from the circuit, all tested OK (I tested capacitance and basic leakage -- I didn't test ESR). The only one that was below nominal capacitance was the 150uF, 450V capacitor. (Just as a side note: It is impossible to get a replacement for this 150uF 450V cap that is as small as the original, so I wired a 100uF and 47uF in parallel. There is just enough space to fit these two caps at right angles to each other inside the heatsink cage.)
Unfortunately, after putting everything back together, the behavior I described above is precisely the same as before (hey, at least I didn't make it worse!).
I'm posting this to see if anyone has other ideas. The duration of the "blink off" outage is pretty consistent, and while I've seen intermittents caused by cold solder joints, I did a pretty thorough inspection, and was unable to detect any obvious cold-solder joints. If it wasn't for all the SMD stuff, I'd just spend fifteen minutes and reflow all the joints.
I'm about ready to throw in the towel on this one, but I thought I'd ask and see if anyone has other ideas. All other components show absolutely no signs of thermal stress.
The board I am working on is absolutely identical to the one shown in the photos in this thread:
Samsung Syncmaster 172N with fried resistors under T1 - No backlight
Thanks!
============
Replacement cap list:
2 - 1000UF 10V ELECT KMG
3 - 470UF 25V ELECT KMG
2 - 1UF 50V ELECT EB
1 - 220UF 25V ELECT EB
1 - 1UF 63V ELECT EB
4 - 47UF 25V ELECT EB
1 - 4.7UF 50V ELECT EB
1 - 100UF 450V ELECT KXG + 47UF 450V KXG
1 - 47UF 50V ELECT
It makes no unusual sounds and, when it is operating, the display is perfect, has normal brightness, and does not flicker.
I have swapped out both the power cable and the cable between the monitor and the computer. Neither change stopped the problem.
This behavior started several months ago, and when it first started, the monitor would blink off for about one second, but only every 5-10 minutes. Thus, it was annoying, but the monitor could still be used. However, the problem slowly got progressively worse, and the monitor is now useless.
After reading several hundred posts in this forum (and elsewhere) I replaced ALL the electrolytic caps (Capxon caps) with 105 degree, low ESR caps (from Digikey, mostly Panasonics). I did not skip any caps. None of the caps were bulging, and when I tested them all after removing from the circuit, all tested OK (I tested capacitance and basic leakage -- I didn't test ESR). The only one that was below nominal capacitance was the 150uF, 450V capacitor. (Just as a side note: It is impossible to get a replacement for this 150uF 450V cap that is as small as the original, so I wired a 100uF and 47uF in parallel. There is just enough space to fit these two caps at right angles to each other inside the heatsink cage.)
Unfortunately, after putting everything back together, the behavior I described above is precisely the same as before (hey, at least I didn't make it worse!).
I'm posting this to see if anyone has other ideas. The duration of the "blink off" outage is pretty consistent, and while I've seen intermittents caused by cold solder joints, I did a pretty thorough inspection, and was unable to detect any obvious cold-solder joints. If it wasn't for all the SMD stuff, I'd just spend fifteen minutes and reflow all the joints.
I'm about ready to throw in the towel on this one, but I thought I'd ask and see if anyone has other ideas. All other components show absolutely no signs of thermal stress.
The board I am working on is absolutely identical to the one shown in the photos in this thread:
Samsung Syncmaster 172N with fried resistors under T1 - No backlight
Thanks!
============
Replacement cap list:
2 - 1000UF 10V ELECT KMG
3 - 470UF 25V ELECT KMG
2 - 1UF 50V ELECT EB
1 - 220UF 25V ELECT EB
1 - 1UF 63V ELECT EB
4 - 47UF 25V ELECT EB
1 - 4.7UF 50V ELECT EB
1 - 100UF 450V ELECT KXG + 47UF 450V KXG
1 - 47UF 50V ELECT
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