Samsung Syncmaster 245BW

[stewart710]

Hi, I'm a longtime lurker around here and have fixed a few lcd's with the help of some of these threads, so thank you in advance. I can't find much info on common issues with this 24" LCD. I ran across a couple of websites with people mentioning my exact problem, but no solution. The monitor powers on, the blue power Led comes on, but there is no image displayed. I have tried shining a light at it, but cannot see any image. I tried this with a DVI cable and VGA cable hooked up to my computer, no dice. The only thing I did notice is that my computer can detect the monitor and knows what resolutions it supports. Also after the computer goes to standby the blue Led on the monitor starts blinking. It comes back on when I wake the computer. This suggests that the lcd motherboard is functioning properly.

So I popped open the case, kind of annoying design, no screws just those pop tabs around the edges. I couldn't find any evidence of bulging caps, even though they are CapXon on the inverter and SamWha on the power board. The motherboard (or whatever it's called) has only polymer caps, so nothing obvious there. I replaced the 4 Capxon 220uf 35v (with Elna RJH caps, I know someone is gonna ask) guys on the inverter, but it didn't help. I then moved onto the power board. Both glass fuses are working. I replaced a couple of SamWha 100uf 35v with 2 100uf 25v caps (KY series, forgot the manufacturer). The transformer handles up to 24v, so I figured this was ok temporarily. No change. I looked at the power board and noticed a little evidence of heat on one of the diodes (FCH20A10). I removed it and it tests out OK. There is a slight bit of voltage getting through but it is like .002v difference when I put the + on the cathode and the black on the outer legs of the diode. I am kind of stumped here. Anyone have any suggestions?

[PlainBill]

Originally Posted by stewart710

Hi, I'm a longtime lurker around here and have fixed a few lcd's with the help of some of these threads, so thank you in advance. I can't find much info on common issues with this 24" LCD. I ran across a couple of websites with people mentioning my exact problem, but no solution. The monitor powers on, the blue power Led comes on, but there is no image displayed. I have tried shining a light at it, but cannot see any image. I tried this with a DVI cable and VGA cable hooked up to my computer, no dice. The only thing I did notice is that my computer can detect the monitor and knows what resolutions it supports. Also after the computer goes to standby the blue Led on the monitor starts blinking. It comes back on when I wake the computer. This suggests that the lcd motherboard is functioning properly.

So I popped open the case, kind of annoying design, no screws just those pop tabs around the edges. I couldn't find any evidence of bulging caps, even though they are CapXon on the inverter and SamWha on the power board. The motherboard (or whatever it's called) has only polymer caps, so nothing obvious there. I replaced the 4 Capxon 220uf 35v (with Elna RJH caps, I know someone is gonna ask) guys on the inverter, but it didn't help. I then moved onto the power board. Both glass fuses are working. I replaced a couple of SamWha 100uf 35v with 2 100uf 25v caps (KY series, forgot the manufacturer). The transformer handles up to 24v, so I figured this was ok temporarily. No change. I looked at the power board and noticed a little evidence of heat on one of the diodes (FCH20A10). I removed it and it tests out OK. There is a slight bit of voltage getting through but it is like .002v difference when I put the + on the cathode and the black on the outer legs of the diode. I am kind of stumped here. Anyone have any suggestions?

Quite a few. The flashlight trick sometimes works, sometimes doesn't. It seems to depend on the characteristics of the panel. The symptoms you describe suggest a non-functioning inverter.

I'd like two more pictures, and you can make one test. I'd like better pictures of the bottom of the board, covering the area around the connector to the inverter, and another covering the connector to the logic card. There are labels there that I can't read.

Also, there is a fuse on the inverter. Have you checked that?

PlainBill

[stewart710]

Hi Bill, thanks for taking the time to look at this. I checked what I believe is the fuse on the inverter and it is OK. It is labeled 125v 6.3A and it is a white rectangular surface mount chip. Here are some pics of the logic board and the back of the power board that you asked for.

[PlainBill]

Originally Posted by stewart710

Hi Bill, thanks for taking the time to look at this. I checked what I believe is the fuse on the inverter and it is OK. It is labeled 125v 6.3A and it is a white rectangular surface mount chip. Here are some pics of the logic board and the back of the power board that you asked for.

OK, a couple of points. One is that I am pretty good at reading legends on PC boards. I also can read upside down. Combine the two - I'm not so good.

On the connector to the inverter there are sections labeled +24V, GND, SOS(?), BL, A_DIM, and ST/P DIM Check for the presence of +24 volts, and the BL pin should toggle when you hit the power button on the monitor. I don't have a clue what SOS means other than something inedible served in the high school cafeteria.

On the power connector to the logic card, please verify the voltages are present.

PlainBill

[stewart710]

I'm an idiot, sorry I didn't even notice I did that. Here are the power boards right side up. I checked the voltage going to the inverter board: the +24v are putting out .229v and the BL is toggling from .18v (off) to ~.2v then back down to ~0v when switched on. I just realized you asked for the logic board side, not the inverter, I'll have to try again tomorrow. The way this thing is put together is very strange. The only way I could test it with everything still plugged in was to use the terminals on the connector on the inverter coming form the cabling that goes to the power board. I'm heading to bed for the night, but I'll be back at it tomorrow evening. Thanks again.

[PlainBill]

Originally Posted by stewart710

I'm an idiot, sorry I didn't even notice I did that. Here are the power boards right side up. I checked the voltage going to the inverter board: the +24v are putting out .229v and the BL is toggling from .18v (off) to ~.2v then back down to ~0v when switched on. I just realized you asked for the logic board side, not the inverter, I'll have to try again tomorrow. The way this thing is put together is very strange. The only way I could test it with everything still plugged in was to use the terminals on the connector on the inverter coming form the cabling that goes to the power board. I'm heading to bed for the night, but I'll be back at it tomorrow evening. Thanks again.

Sounds like this may be a case of no +24 Volts out of the power supply.

PlainBill

[Radio Fox]

Originally Posted by stewart710

...I then moved onto the power board. Both glass fuses are working. I replaced a couple of SamWha 100uf 35v with 2 100uf 25v caps (KY series, forgot the manufacturer). The transformer handles up to 24v, so I figured this was ok temporarily...

I am wondering why you chose the 100uF caps to replace? The more likely candidates to go faulty would be the higher value caps, such as 1000uF.

[PlainBill]

Originally Posted by Radio Fox

I am wondering why you chose the 100uF caps to replace? The more likely candidates to go faulty would be the higher value caps, such as 1000uF.

Most SMPS controllers use one or two electrolytic caps in the 22 - 100 µF range. These provide filtering for start-up and run power. When these fail they do not provide any visual sign. As a matter of routine, it is prudent to replace them. It is elating to replace $9.00 in caps and bring back a monitor from the dead. It is much less delightful to open the monitor up two months later to replace $.50 in caps.

PlainBill

[Radio Fox]

Originally Posted by PlainBill

Most SMPS controllers use one or two electrolytic caps in the 22 - 100 µF range. These provide filtering for start-up and run power. When these fail they do not provide any visual sign. As a matter of routine, it is prudent to replace them. It is elating to replace $9.00 in caps and bring back a monitor from the dead. It is much less delightful to open the monitor up two months later to replace $.50 in caps.

PlainBill

Yep. I agree entirely.

Only a couple of weeks ago I replaced 9 capacitors in a faulty Hyundai N91W. 5 of them were bulging, but I thought I would replace the other 4 large ones in the general area of the others (all Samxon). I replaced them with Panasonic FM's. There was only 1 other electrolytic on the board that I left. It was a small Samxon 47uF 25v.

After just 2 weeks the monitor failed again! Yep, it was the 47uF. The only elctrolytic that I didn't change! It was reading 6 Ohms on the ESR meter. Changed it yesterday for a Panasonic. Working again...so far.

Anyway, I was wondering why stewart710 changed those 2 only, when there are 14 electrolytics on the board, but as he has now said, it was a typo, & it was the 1000uF caps that were changed.

[stewart710]

Originally Posted by Radio Fox

Yep. I agree entirely.

Only a couple of weeks ago I replaced 9 capacitors in a faulty Hyundai N91W. 5 of them were bulging, but I thought I would replace the other 4 large ones in the general area of the others (all Samxon). I replaced them with Panasonic FM's. There was only 1 other electrolytic on the board that I left. It was a small Samxon 47uF 25v.

After just 2 weeks the monitor failed again! Yep, it was the 47uF. The only elctrolytic that I didn't change! It was reading 6 Ohms on the ESR meter. Changed it yesterday for a Panasonic. Working again...so far.

Anyway, I was wondering why stewart710 changed those 2 only, when there are 14 electrolytics on the board, but as he has now said, it was a typo, & it was the 1000uF caps that were changed.

Thanks for catching my mistake. In the stuff I have fixed successfully, it seems there are normally multiple caps with problems and at least one of them has visible signs. So I normally replace all the caps of a given size/brand that show any signs of failing or ones that are known to cause problems. If it works, then I would go back and order the correct parts to replace them all. If I had the correct sizes of caps for the rest of the board on hand, I would replace them as well. I just wanted to make sure that I wasn't barking up the wrong tree before I ordered anything. If the best course of action to replace every cap on the power board now before proceeding, I would. I just wanted to get some help before I go blindly ordering parts that may not fix the problem.

[stewart710]

Bill,
So the 24V is only connected to the inverter side, not the logic board, which reads ~0.225v. the Logic board gets a connection labeled PSON which reads ~3.2v and 5.2v Standby which reads 5.2v. It also has 3x connections that are supposed to supply 5.3v, but they all read -0.001v.

[stewart710]

Originally Posted by Radio Fox

I am wondering why you chose the 100uF caps to replace? The more likely candidates to go faulty would be the higher value caps, such as 1000uF.

You're right, it was a typo. They were 1000uF caps which was part of the reason I chose, also because I had replacements handy.

[drb]

Hey, new member here (and impressed at the level of experience other members here possess). Noob at this sort of thing, but able to figure things out when needed. I've got the same exact problem as the OP. Would love for others to post if they've had any new progress since the last few posts.

Many thanks!

[cloepula]

Hello to all you guys !!
Me to trying to find the solution on same monitor, samsung syncmaster 245b. Simptoms are the same like yours here. When try to power on, only blue led on the on button lit blue. Monitor dont start, inverter dont start, but there is a 5.2v standby power. This is the only voltage from power supply. No 24v or 5.3v, Found burned resistor RB805 68ohm. All caps ok, tested with esr tester, and tested for capacity. Tested all other resistor, all found ok. When testing for voltages on vcc pin on ice3B0365J found strange voltage, 11v-16v dc fast changing values, testing for ac was 30v-35v on the same pin (. Tested diodes for vcc pin power and found all ok, then try to change this two diodes with similar, and again nothing, same strange and not stable voltages on vcc pin. Other two integrated circuit are without any power supply. Tested optoisolators , and all seams good. Tested all other diodes and rectifyers, and everithing seams ok, but power supply just dont start. So for now, only one resistor burned, and changed. Ordered new ice3b0365J for 5 euros and maybe in 2-3 days will arive. I dont know if this will fix the supply but i will try this solution, and if you didnt solve the bug on this monitor, and dont have any sugestion or news on your problem, wil change the ic and see if this was the reason for dead supply. Any sugestion or help is greatly apricieted.

[stewart710]

I never made it any farther than you see in the thread. the monitor is still sitting apart in my basement. I was beginning to think about getting rid of it. Sounds like you've gotten a lot deeper into this than I have. I'd be interested to hear how you make out changing the IC. Please keep me posted.

[cloepula]

This is the photo made from you, i only marked burned resistor.

[cbytes]

Originally Posted by cloepula

This is the photo made from you, i only marked burned resistor.

I had the exact same issue as OP with my 245bw. I first checked caps, only bulged ones were on the inverter board. I replaced the 4 35v 220uf caps. Still had the same issue. After some more digging I was redirected to this thread. I had a burnt out resistor, same one that cleopula pointed out. I didnt have a 67.4 ohm handy so I threw in a 50 ohm resistor and the monitor works great now just wanted to let everyone know.

[mladen82]

Originally Posted by cloepula

Hello to all you guys !!
Me to trying to find the solution on same monitor, samsung syncmaster 245b. Simptoms are the same like yours here. When try to power on, only blue led on the on button lit blue. Monitor dont start, inverter dont start, but there is a 5.2v standby power. This is the only voltage from power supply. No 24v or 5.3v, Found burned resistor RB805 68ohm. All caps ok, tested with esr tester, and tested for capacity. Tested all other resistor, all found ok. When testing for voltages on vcc pin on ice3B0365J found strange voltage, 11v-16v dc fast changing values, testing for ac was 30v-35v on the same pin (. Tested diodes for vcc pin power and found all ok, then try to change this two diodes with similar, and again nothing, same strange and not stable voltages on vcc pin. Other two integrated circuit are without any power supply. Tested optoisolators , and all seams good. Tested all other diodes and rectifyers, and everithing seams ok, but power supply just dont start. So for now, only one resistor burned, and changed. Ordered new ice3b0365J for 5 euros and maybe in 2-3 days will arive. I dont know if this will fix the supply but i will try this solution, and if you didnt solve the bug on this monitor, and dont have any sugestion or news on your problem, wil change the ic and see if this was the reason for dead supply. Any sugestion or help is greatly apricieted.

I find burned resistor RB805 burned too.

[stewart710]

My resistor appears fine, reads 67.4 ohms

[cloepula]

Did you test the ics for supply voltage?? Try to test to see how is your voltages on the chip. On your picture i will mark test point for dc power supply on this chip, try to test ac voltage on the same test point. Let see how is yours reading .