samsung 245bw blank screen, pop then no power.

[b6echufr]

Hi,

I have a samsung 245bw with the BN44-00195A power board. I have been reading up on this forum about it. I see many people have had issues. My problem does not seem to be the standard blank screen but a working led on the power button. My monitor worked fine then went dark. I turned it off. when I turned it back on I heard a loud pop and the power led on the power button went out. After searching this forum I was unable to find the same issue. I do not see any bad or bulging caps. The only damage I can find is a smoked resister. It is the blue one just north east of the large 82uF cap. I have included a picture. I am guessing here but I suspect a resister blowing would not make that kind of noise. The fuses test good. With a little guidance I should be able to fumble my way through this. Does anyone think that this one resister could cause the problem? If not what should I look at next? I do not mind testing but I am not comfortable with doing a live power test with out some more information on how to safely conduct it. Sorry for the poor photos. They are from my cell phone. Its the best I have on hand at this time to take a picture.

Thank you.

[selldoor]

Re: samsung 245bw blank screen, pop then no power.

If you have read the MONSTER thread on this set every test imaginable is included.
One thing that is stressed is to remove all the yellow glue. Have you done that?
It actually looks as though the glue has gone conductive and shorted out the resistor.
Lift one leg of the resistor and check it. If it is faulty until it is replaced there is not much more that can be done. You may as well order the 68ohms resistors to replace the cluster of three as that is the other classic fault.

[Rtech]

Re: samsung 245bw blank screen, pop then no power.

What is the colour code of the Resistor ?/also its possible that the transistor/Mosfet on the Heatsink next to it may have also failed...do need better photos ??

[b6echufr]

Re: samsung 245bw blank screen, pop then no power.

I have read a number of large threads however I can not say for certain if I have read the one you have referred to Selldoor.

I plan to remove the glue. I wanted to get some pictures in before I chance breaking something. That glue does not want to let go. Any tips on this? I have read about just using a pick and pliers. I'm doing that now but I fear damaging the fragile connections/components.

Where the cluster of three usually is I have a cluster of 2. The third item is small and black. It is also totally covered in glue so until I scrape it I am not sure what it is.

The blue resister is (top to bottom) red, red, silver, gold.

The Mosfet next to the blown resister appears undamaged. I suspect a Mosfet blowing could make a loud pop. Could a resister make that noise?

I will try to include better photos tonight.

Thanks for the help.

[selldoor]

Re: samsung 245bw blank screen, pop then no power.

Yes - sorry you have the other board so 2 resistors and a diode so not usually a problem
except for the glue.
The thread I refer to is here
https://www.badcaps.net/forum/showthread.php?t=9343
It covers both boards - One poster with your board did not have any faulty components it just shorted out with the glue!
I dont see why resistors shouldnt pop when they blow. please test it.

[euromatlox]

Re: samsung 245bw blank screen, pop then no power.

There are two varistors on board, 3D-15 and 10D751 (if I read it right on a broken board in front of me at the moment). Check if burn marks or pieces missing. Also check fuses (measure using diode tester/ohmmeter). I once heard a loud pop when turning on a computer, and psu had broken fuse and varistor had piece missing. Those components don't fail without a reason, there must be something shorted on board in this possible scenario. If you try to repair it, in any case the three electrolyte capacitors near Sanken 8008hfe should be replaced (and 8008hfe checked).

[budm]

Re: samsung 245bw blank screen, pop then no power.

That is the 0.22 Ohm fusible resistor (RM801?) which feed the B+ from that 82uf 450V cap to the 24V SMPS power supply section. The two MOSFETs for 24V SMPS are on that heatsink, so you need to check both MOSFETs for short.
The diagram I attached are real close to what you have, the designators may not match but the connection and the operations are real close, I use it for troubleshhoting -195A board.
If you trace the board and you can see that one end of the resistor is connected to the + of the cap, another end of the resistor is connected to the Source pin of one of the two MOSFET.

By the way, are you getting any DC outputs at all from the connectors?

[Rtech]

Re: samsung 245bw blank screen, pop then no power.

If you do not know how to check the mosfets as advised,then the 'sticky' 2 secs to black,Post #13,gives you one test,and/or the following may be of help:-
http://www.4qdtec.com/mostest.html

[b6echufr]

Re: samsung 245bw blank screen, pop then no power.

Thank you all for the help. I will check the resister but I'm sure its shot and in need of replacement. I will also read up on how to check the MOSFETs and then test them. I think I may need a solder sucker and a better iron then my RS one though. I will have to research what to buy.

I have not done any live power testing yet. I am not comfortable doing that without some input on how to safely accomplish it.

The glue does not want to come off. I seem to be doing more damage then good. Any tips on how to remove it without damaging or twisting up components?

Thanks.

[selldoor]

Re: samsung 245bw blank screen, pop then no power.

It is not easy.lots of patience and time needed - you can try to soften by repeat applications of isopropyl alcohol.

There are a lot of non power tests in this guide written by retired caps
https://www.badcaps.net/forum/showthread.php?t=10419
start at post19

[budm]

Re: samsung 245bw blank screen, pop then no power.

I use Denatured Alcohol to sofeten the glue before removing them.
You can put a 75 Watts lamp in place of one the of the fuse (there are two main AC fuses on your board, one is on the Neutral side, anothe one is on the Hot side (this is the one you want to remove and unstall the lamp in its place)).

[b6echufr]

Re: samsung 245bw blank screen, pop then no power.

Thank you for the tips. I will try the alcohol. What is the purpose of replacing the fuse with a lamp? My fuses did not blow.

Thanks.

[budm]

Re: samsung 245bw blank screen, pop then no power.

Just in case you slip the probe while testing the voltage, the lamp will automatically limit the current draw and the voltage to the board (when lamp lights up brightly due to shorted circuis). You should also the AC power through GFCI outlet or use isolation transformer.
I use this setup:
http://s807.photobucket.com/user/bud...38847330675986

[b6echufr]

Re: samsung 245bw blank screen, pop then no power.

budm,

Does that setup you have linked still require using a bulb in place of one of the fuses? Or does that setup replace having to put a bulb in place of the fuse? Also when testing the power supply do you put the board on a rubber isolation mat?

Thanks

[budm]

Re: samsung 245bw blank screen, pop then no power.

No, the box will put the lamp in series with the load (the TV or the board you are working on), the fuses on the board will be in place.
Yes I do put the board I ma working on cardboard or rubber pad (but not black rubber pad that has corbon impregnated which will conduct due to carbon)

[b6echufr]

Re: samsung 245bw blank screen, pop then no power.

ok that sounds good. I was thinking of one of the high voltage mats we stand on at work to keep from electrocuting our selfs when we throw the main breaker. I will build one of those boxes. I'm also going to research a better soldering iron so I can get that resister out to test.

[euromatlox]

Re: samsung 245bw blank screen, pop then no power.

Don't know details of this model, but Samsung 245b has also fuses on inverter and video board (located under metal plate), the logic board might be fuse-free but can't remember right now. I found it hard to believe that a resistor can make extreme loud sound..and if it can, then the current must be very big and some fet or regulator or cap or something shorted there. If you know for sure that a very noisy explosion like sound was heard, carefully check everything.

[b6echufr]

Re: samsung 245bw blank screen, pop then no power.

There was definitely 1 pop. I was sitting right in front of it when it happened. It sounded like it came from the area of the power board. The pop is what worries me. Its starting to sound like I should just look for a new power board.

[Rtech]

Re: samsung 245bw blank screen, pop then no power.

Don't be put off by the 'pop', as explained if the resistor is blown,chances are the mosfet may have been the cause of the noise,and if so then these are obtainable and reasonably priced.

[euromatlox]

Re: samsung 245bw blank screen, pop then no power.

You should look for BN44-00173A instead of BN44-00195A, if you decide to change power board. I have made this switch for a Samsung 245b+ monitor. Much better board and 100% compatible (same connectors). Some for sale at ebay but price is pretty high. If in original condition, just replacing three 68ohm resistors and some electrolytic capacitors will very likely be enough (those are typical fail causes for that board).