Hello badcappers!
I'm an IT guy and most of the time I deal with operating systems and networking.
In the past when a colleague of mine reported a monitor as defected I simply substituted it and drop the old one into the junk bin, because I don't have an electronics background.
But in the last months I started to try to learn a bit about SMPS and repair them. Almost every month I got a couple of not working videos sent back to me and so I'm lucky I got material to work on! You know, my primary goal now is to learn new things; having a monitor brought back to life is a nice plus.
So, right now I got two LCD's Samsung Syncmaster 710; one had the following symptoms:
- led slowly blinking even with input signal from PC
- nothing on screen, not even the 2 inital seconds
- with a torch light I can faintly see something on screen
From what I've learned in this great forum they are symptoms of a problem with the inverter.
Anyways I opened up the monitor and I found 2 bulging caps (820uF 25V); measured them with an ESR tester (yep! I bought one) and they both gave 0,60 Ohms. I found also a 330uF 25V cap near the inverter section with an ESR of 0,60 Ohms. So I changed the 820uF caps with two 1000uF and the 330uF. Result: when I turned on the video the led started to blink very fast and I heard a ticking sound, as if it was resetting itself.
Then, as a test, I changed ALL the caps, even the big filter 400V one (remember: I am learning), connected everything: same as above (fast led and ticks). I even connected the power supply board to the other video: same symptoms.
I know that in cases like this you often ask to take voltage measures, but I don't feel safe to do so, at least not until I got myself an isolation transformer and become more knowledgeable about this stuff.
I attach a couple of photos; got any clue of what should I check?
Thanks in advance
--
rob
I'm an IT guy and most of the time I deal with operating systems and networking.
In the past when a colleague of mine reported a monitor as defected I simply substituted it and drop the old one into the junk bin, because I don't have an electronics background.
But in the last months I started to try to learn a bit about SMPS and repair them. Almost every month I got a couple of not working videos sent back to me and so I'm lucky I got material to work on! You know, my primary goal now is to learn new things; having a monitor brought back to life is a nice plus.
So, right now I got two LCD's Samsung Syncmaster 710; one had the following symptoms:
- led slowly blinking even with input signal from PC
- nothing on screen, not even the 2 inital seconds
- with a torch light I can faintly see something on screen
From what I've learned in this great forum they are symptoms of a problem with the inverter.
Anyways I opened up the monitor and I found 2 bulging caps (820uF 25V); measured them with an ESR tester (yep! I bought one) and they both gave 0,60 Ohms. I found also a 330uF 25V cap near the inverter section with an ESR of 0,60 Ohms. So I changed the 820uF caps with two 1000uF and the 330uF. Result: when I turned on the video the led started to blink very fast and I heard a ticking sound, as if it was resetting itself.
Then, as a test, I changed ALL the caps, even the big filter 400V one (remember: I am learning), connected everything: same as above (fast led and ticks). I even connected the power supply board to the other video: same symptoms.
I know that in cases like this you often ask to take voltage measures, but I don't feel safe to do so, at least not until I got myself an isolation transformer and become more knowledgeable about this stuff.
I attach a couple of photos; got any clue of what should I check?
Thanks in advance
--
rob
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