Re: Samsung Syncmaster 245BW
The second failed monitor has been repaired and is running again. One of the 68 ohm resistors was open. I replaced all three. I inspected the caps and they all looked good. It was six months between the first monitor failing and this one. I wonder how long it will be before monitor number three fails.
dbinokc
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Last Activity: 11-19-2017, 01:04 AM
Joined: 10-21-2011
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Re: Samsung Syncmaster 245BW
The second of my three 245BW monitors went dead today. Same symptoms as before, blue light and no display. It will be interesting to see if it is the same resistor problem as before or something else. Will post results or ask for help if I get stuck.Leave a comment:
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Re: Samsung Syncmaster 245BW
The monitor is working now. It turned out to be that RB803 was open as well. So that is two bad resistors on this monitor. I replaced with a 2.2 ohm and it works. Now I just have to put it back together.
Since RB803 and the 68 ohm resistors both have that coating on the leads, I have to wonder if it is causing some kind of corrosion that is causing the opens.
I appreciate everyones patience with my bumbling around some. I normally build electronic projects, not try to fix them. I only bothered trying to fix this time, because...Leave a comment:
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Re: Samsung Syncmaster 245BW
Hooked up my isolation transformer and a ground off the negative side CP803.
I finally have some voltages that make a little more sense now. I am seeing 180VDC off of DB801 on both sides.
I removed the cables from the video side and checked for 24V. I found no 24V. I also checked FB802S and it was not open.
I probed VCC of ICB801S and found about 15V.
I probed VCC of the F92222L and found 0 volts. I also probed off of the
68ohm resistors and found no voltage present there as well.
It looks like...Leave a comment:
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Re: Samsung Syncmaster 245BW
I am probing with my oscilloscope, not a multimeter. I have been grounding to the chassis, but I was planning to ground to the negative side of the bridge since I have the isolation transformer setup on the monitor.
I just need to find a place to connect. I can not really flip the board over while the power is on because of the cables. If I can not find a good place to connect to on the top side, I will solder a wire on the bottom side and and get to the hotside ground that way.Leave a comment:
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Re: Samsung Syncmaster 245BW
I got my replacement fuses. I did the video card test. I removed the connectors from the video card side. When I probed the 24V I saw a 160V pk-pk AC waveform at the 24V. With the card connected, this went to 0V.
I need to figure out where I can get a ground reference on this board. I find it hard to believe I have a real 160VAC running around on 24V.
Just as a later edit, I have my isolation transformer connected to the monitor now. I just need to find a good place to attach my ground lead, so I can get rid of AC showing up all over....Last edited by dbinokc; 11-03-2011, 10:35 PM.Leave a comment:
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Re: Samsung Syncmaster 245BW
@Toasty,
I did some more checking last night. I rechecked the other two 68 ohm resistors to make sure thay had not opened up after my replacing the first one. They were still good.
I was doing some probing and accidentally hit the hot hotsink with the grounded portion of scope probe. Should have setup that isolation transformer after all! Before I can continue, I will need to get a replacement fuse.
I did not get a chance to try your disconnection suggestion before I blew the fuse.Leave a comment:
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Re: Samsung Syncmaster 245BW
I found one bad resistor in the 3 on my board. Before removing and/or ordering you may want want to check them on the board with a multimeter first. They should each read 68 ohms. The bad one on my board read as an open.Leave a comment:
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Re: Samsung Syncmaster 245BW
The number on mine is BN44-0173A as well.Leave a comment:
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Re: Samsung Syncmaster 245BW
Sorry, I meant Toasty, not Danweil...Leave a comment:
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Re: Samsung Syncmaster 245BW
I did a little more checking last night before the replies were posted. I checked a few components. At first I thought the problem was at DB871. I pulled the component and the diode tested good. I suppose it could have problems with breakdown Next I pulled ICB801S thinking maybe the 292V going in at pins 4 and 5 had blow through the chip somehow and was making it to pin 7. Looking at pin 7 showed the same waveforms as before.
I saw the comments about RB807,RB806 and RB805 sometimes failing. I ohmed out those resistors. I did find one open. (Never...Leave a comment:
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Re: Samsung Syncmaster 245BW
I have a 245BW that shows no display, but the blue power switch lights up.
I have already pulled the monitor apart and started checking some voltages.
There is no 24V out. No obvious bulging caps or blown components.
At first I thought I had found a clue when I connected my multimeter to look at VCC of ICB801S. I saw about 15V AC. To get a closer look I connected my scope and I am seeing see -150VAC rectified which makes absolutely no sense. Every component in this part of the circuit should be blown to bits! Not sure why...Leave a comment:
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