Samsung SyncMaster T240 - 2 seconds then black problem

[anacryon]

O.K. first thank you all for the great posts. I have learned more about "Bad Caps" then I ever thought I wanted to know. Thank you in advanced as well for any comments you can make to help me.
I have read as many posts as I could before posting, so please go gentle on me if I miss something.

Here it is:

My 2 year old SyncMaster T240 started flickering early yesterday then eventually presented the classic "comes on for 2 seconds then goes off" symptoms. The only difference is that I can get the on-screen "Source" logo to display as I push the "Source" button on the side of the chassis. However, as soon as it hits the Input with any signal, DVI, HDMI, or VGA it does the "hey here I am then, hey there I go" thing.

I have taken the monitor apart and looked at the whole Inverter board. I cannot see any signs of obvious CapXon bulging, but I do see a slightly darkened area near two of the 820uF caps. that are near the long box coil (sorry, don't know the right name for it, but would love to know).
I am planning on proceeding with the Cap replacement procedures that have been listed in many posts here, however I have two problems.

1. I don't know if the dark browning I see on the board means something really bad, of is just a sign of bad soldering at the plant
2. The 820uF 25v 10mm X 25mm caps on the board are back ordered pretty much everywhere (I tried Digi, Mouse, several others both for Panasonic as well as any other low ESM brands, no luck). So I was hoping for some suggestions on where to get them, or some alternative replacements.

I have, or will attach picture of all the items I described above. Bellow please see a legend for the main up-side board picture showing the placement of all the interesting items that I could see.

A - 250V 15 AH fuse - seems to be ok but hard to tell because it is opaque not clear
B - 4 x 820uF 25v 10mm x 25mm 1050 Sam Young capacitors - no obvious signs of bulging
C - 2 x 1000uF 10v 10mm x 12.5mm 1050 Sam Young capacitors - again no obvious signs of defect
D - 330uF 10v 7mm x 10 mm Rubycon capacitor - same
E- 47uF 50v 1050 Sam Young capacitor - same
G - dark brown "burn" indication

Any pointers on the above would be appreciated. I was wondering if I could use higher 1000uF cap for the 820's because they are in stock. I also would like to know what that long wire warp is right next to the set of two 820's off by themselves is and whether or not it could be related to the problem stated above.

Thanks much
Anacryon

[Wizard]

Re: Samsung SyncMaster T240 - 2 seconds then black problem

Use those 1000uF, make sure they are low ESR with high freq type (similar to SMPS capacitors). Should do whole job on capacitors, about six in all.

You may need to replace the transformer if replacing capacitors does not fix the issues.

Cheers, Wizard

[PlainBill]

Re: Samsung SyncMaster T240 - 2 seconds then black problem

O.K. first thank you all for the great posts. I have learned more about "Bad Caps" then I ever thought I wanted to know. Thank you in advanced as well for any comments you can make to help me.
I have read as many posts as I could before posting, so please go gentle on me if I miss something.

Here it is:

My 2 year old SyncMaster T240 started flickering early yesterday then eventually presented the classic "comes on for 2 seconds then goes off" symptoms. The only difference is that I can get the on-screen "Source" logo to display as I push the "Source" button on the side of the chassis. However, as soon as it hits the Input with any signal, DVI, HDMI, or VGA it does the "hey here I am then, hey there I go" thing.

I have taken the monitor apart and looked at the whole Inverter board. I cannot see any signs of obvious CapXon bulging, but I do see a slightly darkened area near two of the 820uF caps. that are near the long box coil (sorry, don't know the right name for it, but would love to know).
I am planning on proceeding with the Cap replacement procedures that have been listed in many posts here, however I have two problems.

1. I don't know if the dark browning I see on the board means something really bad, of is just a sign of bad soldering at the plant
2. The 820uF 25v 10mm X 25mm caps on the board are back ordered pretty much everywhere (I tried Digi, Mouse, several others both for Panasonic as well as any other low ESM brands, no luck). So I was hoping for some suggestions on where to get them, or some alternative replacements.

I have, or will attach picture of all the items I described above. Bellow please see a legend for the main up-side board picture showing the placement of all the interesting items that I could see.

A - 250V 15 AH fuse - seems to be ok but hard to tell because it is opaque not clear
B - 4 x 820uF 25v 10mm x 25mm 1050 Sam Young capacitors - no obvious signs of bulging
C - 2 x 1000uF 10v 10mm x 12.5mm 1050 Sam Young capacitors - again no obvious signs of defect
D - 330uF 10v 7mm x 10 mm Rubycon capacitor - same
E- 47uF 50v 1050 Sam Young capacitor - same
G - dark brown "burn" indication

Any pointers on the above would be appreciated. I was wondering if I could use higher 1000uF cap for the 820's because they are in stock. I also would like to know what that long wire warp is right next to the set of two 820's off by themselves is and whether or not it could be related to the problem stated above.

Thanks much
Anacryon

Going with larger caps should be no problem provided you use low ESR (not ESM) types such as Panasonic FMs, etc.

The 'long box coil' is the inverter output transformer. This appears to be two transformers on a single frame.

I've seen browning like that when the transformer drivers were mounted on the underside of the board. That is not the case here. I would suggest removing the transformer from the board and examining it carefully. I would replace it if there are signs of arcing.

PlainBill

[anacryon]

Re: Samsung SyncMaster T240 - 2 seconds then black problem

Thanks for the replies, (I meant ESR, my finger just rebelled and hit M instead...to the rack with you finger !!!) now it's time to wait for shipping and another free moment to pull out the old solder kit.

I'll let you know how it goes.

Sincerely,
Anacryon

[PlainBill]

Re: Samsung SyncMaster T240 - 2 seconds then black problem

Thanks for the replies, (I meant ESR, my finger just rebelled and hit M instead...to the rack with you finger !!!) now it's time to wait for shipping and another free moment to pull out the old solder kit.

I'll let you know how it goes.

Sincerely,
Anacryon

My keyboard does that all the time. I think it's some sort of a virus. I've replaced it once, and now the new keyboard is doing it.

PlainBill

[DUCE]

Re: Samsung SyncMaster T240 - 2 seconds then black problem

Glad I found this post! I am a noob with the same exact monitor and problem. Hope we can take this post all the way to showing a completed fix.

I bought mine on e-pay and it was claimed to have a blown backlight. I picked one up on LCD parts net before digging into the monitor case assuming it would be a plug and go fix. That was an extremely dumb assumption!! Turns out it uses 4 backlights (2 top and bot) and after seeing the power board I could tell that it was probably failing there and not at the lights.

-Please check my logic here anybody, because I was just using basic troubleshooting ideas!

Powering it up while having the backlights exposed showed that the power line from board to lights was not providing anything to the top set of lights. I tested this by having both lines connected. The bottom set did the classic pulse with 2 second delay but the top did nothing. I swapped the power lines over so the "good" line was feeding to the dead light area and nothing at all.

Obviously the top set of lights could be blown and I will definitely be looking into that further, but I suspect the problem is at the power board. I attached some pics to show what I found because it appears that the board had blown caps and was fixed but possibly that was not the solution...or the caps are not correct...or the caps worked until the inverter failed.

I was going to test output at the light connection on the power board with my multimeter but the probes were very close together and I didnt want to cross them while powered up. I have to get around that tonight to get a better picture of what is really going on. I have no idea how to test the inverter output properly.

Hope this does not seem like a hi-jack but I am pretty sure I the origional poster and I have the same problem. It all sounds like inverter and caps to me but I could be wrong.

[PlainBill]

Re: Samsung SyncMaster T240 - 2 seconds then black problem

Glad I found this post! I am a noob with the same exact monitor and problem. Hope we can take this post all the way to showing a completed fix.

I bought mine on e-pay and it was claimed to have a blown backlight. I picked one up on LCD parts net before digging into the monitor case assuming it would be a plug and go fix. That was an extremely dumb assumption!! Turns out it uses 4 backlights (2 top and bot) and after seeing the power board I could tell that it was probably failing there and not at the lights.

-Please check my logic here anybody, because I was just using basic troubleshooting ideas!

Powering it up while having the backlights exposed showed that the power line from board to lights was not providing anything to the top set of lights. I tested this by having both lines connected. The bottom set did the classic pulse with 2 second delay but the top did nothing. I swapped the power lines over so the "good" line was feeding to the dead light area and nothing at all.

Obviously the top set of lights could be blown and I will definitely be looking into that further, but I suspect the problem is at the power board. I attached some pics to show what I found because it appears that the board had blown caps and was fixed but possibly that was not the solution...or the caps are not correct...or the caps worked until the inverter failed.

I was going to test output at the light connection on the power board with my multimeter but the probes were very close together and I didnt want to cross them while powered up. I have to get around that tonight to get a better picture of what is really going on. I have no idea how to test the inverter output properly.

Hope this does not seem like a hi-jack but I am pretty sure I the origional poster and I have the same problem. It all sounds like inverter and caps to me but I could be wrong.

Please clarify this. I interpret it to say with the 'normal' hook-up the top pair of lights does not work. Reversing the hook-up, neither set of lights work. If that is correct you have two problems.

You are correct, those caps were replaced by someone who missed his true calling - cleaning up after the elephants in the circus.

PlainBill

[DUCE]

Re: Samsung SyncMaster T240 - 2 seconds then black problem

I thought those caps looked a little suspect. There were other signs that the case had been cracked after factory like masking tape on the back plate to hold down wires. I hope that I have not purchased a total dud that I just cant fix but it seems that the last person was a tad careless so maybe they just missed something simple (I hope).

The 2 connections from power board to lights are shown here connected. Basically its just 2 cables that have 4 wires each and they connect to 4 CCFL lights in the screen back plate. Hope that pic and explanation explains what I meant better.

What bothers me and is the same as the OP is the burnt area around the caps and inverter area. My pics dont show it very well but I think both me and the OP have found a weak spot on this board. In my case the caps were obviously replaced but that may or may not have solved the original prob. The blinking on the lower section of lights indicates inverter (as I have learned lately). The scorching around the cap area makes me think that a cap failure could have aided in an inverter failure. Not sure if that is a plausible theory because of my low experience level but the burnt area and blinking CCFL plus the replaced caps seem to leave a bit of a bread trail.

I would like to test the CCFL's to see if they have failed and test my power lines connecting the CCFL's.

The specs for the replacement CCFL:
Strike Voltage 1600
Working Voltage 920
Watts 5.5

Strange voltages there (IMHO) maybe I missed somthing...
http://www.lcdparts.net/ccfldetail3D...ProductID=1600

I have no idea how to test the inverter yet. Thats one I will look into more but any hints or ideas are welcome.

I have scoured the net for a service manual but only found the older model 240T which is quite different so there is no correlation on part numbers and specs.

Basically it seems we are on our own with this monitor for reliable data to use. Maybe somthing will turn up in later searches. At least we have 2 people with similar issues posting here, hopefully the folks with more experience can help us deduce the problem.

[PlainBill]

Re: Samsung SyncMaster T240 - 2 seconds then black problem

I thought those caps looked a little suspect. There were other signs that the case had been cracked after factory like masking tape on the back plate to hold down wires. I hope that I have not purchased a total dud that I just cant fix but it seems that the last person was a tad careless so maybe they just missed something simple (I hope).

The 2 connections from power board to lights are shown here connected. Basically its just 2 cables that have 4 wires each and they connect to 4 CCFL lights in the screen back plate. Hope that pic and explanation explains what I meant better.

What bothers me and is the same as the OP is the burnt area around the caps and inverter area. My pics dont show it very well but I think both me and the OP have found a weak spot on this board. In my case the caps were obviously replaced but that may or may not have solved the original prob. The blinking on the lower section of lights indicates inverter (as I have learned lately). The scorching around the cap area makes me think that a cap failure could have aided in an inverter failure. Not sure if that is a plausible theory because of my low experience level but the burnt area and blinking CCFL plus the replaced caps seem to leave a bit of a bread trail.

I would like to test the CCFL's to see if they have failed and test my power lines connecting the CCFL's.

The specs for the replacement CCFL:
Strike Voltage 1600
Working Voltage 920
Watts 5.5

Strange voltages there (IMHO) maybe I missed somthing...
http://www.lcdparts.net/ccfldetail3D...ProductID=1600

I have no idea how to test the inverter yet. Thats one I will look into more but any hints or ideas are welcome.

I have scoured the net for a service manual but only found the older model 240T which is quite different so there is no correlation on part numbers and specs.

Basically it seems we are on our own with this monitor for reliable data to use. Maybe somthing will turn up in later searches. At least we have 2 people with similar issues posting here, hopefully the folks with more experience can help us deduce the problem.

OK, I'm trying to make this very simple. First of all, the discoloration isn't unusual. Yes, it MIGHT indicate a failed transformer. Or it might be the result of normal heating from the transformer drivers.

I have marked up your picture. Notice I have marked A and B cables, A and B connectors. You have stated that with the present connections the "top" CCFLs (presumably the 'A' set) does not light. What happens if you plug the 'A' cable into the 'B' connector and the 'B' cable into the 'A' connector, then apply power?

PlainBill

[mathog]

Re: Samsung SyncMaster T240 - 2 seconds then black problem

Powering it up while having the backlights exposed showed that the power line from board to lights was not providing anything to the top set of lights. I tested this by having both lines connected. The bottom set did the classic pulse with 2 second delay but the top did nothing. I swapped the power lines over so the "good" line was feeding to the dead light area and nothing at all.

What happens if you leave the bad set unplugged, and the good set plugged in? Will it stay on then? If yes, how about with the other side of the PS driving the good lamps, and the bad lamps not plugged in? Most PS will run happily with no load, but they shut down really fast if they see something that looks like a short. So if you are lucky, what you will find is that both sides of the PS can drive the good lamps, and all you have is bad lamps. That said, even in that case you might want to change all of the lamps if you change any, since the good ones may be very nearly at their end of life.

[PlainBill]

Re: Samsung SyncMaster T240 - 2 seconds then black problem

What happens if you leave the bad set unplugged, and the good set plugged in? Will it stay on then? If yes, how about with the other side of the PS driving the good lamps, and the bad lamps not plugged in? Most PS will run happily with no load, but they shut down really fast if they see something that looks like a short. So if you are lucky, what you will find is that both sides of the PS can drive the good lamps, and all you have is bad lamps. That said, even in that case you might want to change all of the lamps if you change any, since the good ones may be very nearly at their end of life.

This is one of the things that makes me want to tear out what little non-gray hair remains. By design, an inverter will shut down as soon as it senses a lamp that is not drawing any current.

You are right, he has to figure out if he has bad lamps or an inverter problem. You don't do this by leaving one set of lamps unplugged. And this is the reason I asked what happens if he switches lamps and inverter outputs. By his description, he seems to be saying if the connections are swapped NEITHER set of lamps will work. What does that mean?

PlainBill

[mathog]

Re: Samsung SyncMaster T240 - 2 seconds then black problem

This is one of the things that makes me want to tear out what little non-gray hair remains. By design, an inverter will shut down as soon as it senses a lamp that is not drawing any current.

Are you sure of that? I used exactly this method on a Sharp TV and in that instance one side of the inverter would drive lamps when the other wasn't plugged in. As it turned out on that machine both the lamps were working but one half of the inverter was out due to a bad capacitor. Either that inverter was not designed to shut down if unloaded, or perhaps that bad capacitor was leaking enough current internally that both sides of the inverter appeared to be loaded, even though they were not. I did try switching the lamps on this board and it immediately shut down in both positions. Probably because leakage current + CCFL current was too high for the inverter.

The ideal would be to apply the mythical "cheap and effective CCFL testing circuit" directly to the lamps, and so take the inverter completely out of the equation. Unfortunately said circuit has not yet been spotted on these forums.

[PlainBill]

Re: Samsung SyncMaster T240 - 2 seconds then black problem

Are you sure of that? I used exactly this method on a Sharp TV and in that instance one side of the inverter would drive lamps when the other wasn't plugged in. As it turned out on that machine both the lamps were working but one half of the inverter was out due to a bad capacitor. Either that inverter was not designed to shut down if unloaded, or perhaps that bad capacitor was leaking enough current internally that both sides of the inverter appeared to be loaded, even though they were not. I did try switching the lamps on this board and it immediately shut down in both positions. Probably because leakage current + CCFL current was too high for the inverter.

The ideal would be to apply the mythical "cheap and effective CCFL testing circuit" directly to the lamps, and so take the inverter completely out of the equation. Unfortunately said circuit has not yet been spotted on these forums.

The OP's photos leave something to be desired, but the voltage and current sense components are clearly visible. I've marked them on the attached picture. Upon closer examination, I think there is a pretty obvious explanation of why the upper CCFLs don't work. I've marked it 'Overheating, no obvious cause'. What do you think?

Again, what remains to be established is if the upper CCFLs are also defective.

PlainBill

[DUCE]

Re: Samsung SyncMaster T240 - 2 seconds then black problem

I am sorry for contributing to any male pattern baldness PlainBill, being a senior member must be tough but I am glad you have taken the time on this because your comments are spot on.

I didn't know that an inverter was designed to shut down when the lamps are not drawing current.

I did learn somthing useful today while attempting to swap the lamp output lines...the housing around the power plug is hot!!



I will take another stab at it later after the buzzy feeling has stopped.

[Wrog]

Re: Samsung SyncMaster T240 - 2 seconds then black problem

I did learn somthing useful today while attempting to swap the lamp output lines...the housing around the power plug is hot!!

Just in case it hasn't been said (or maybe this is reinforcement) -- only swap plugs with the power disconnected!

[mathog]

Re: Samsung SyncMaster T240 - 2 seconds then black problem

Upon closer examination, I think there is a pretty obvious explanation of why the upper CCFLs don't work. I've marked it 'Overheating, no obvious cause'. What do you think?

I think that it was a fluke leaving half the inverter unplugged worked on the Sharp TV.

As for the brown spot, isn't that in the same position as the brown mark on one side of the transformer on the other side of the board? In your marked up picture of the other side it is just below the "'A; connector" label. At least, that's the way it looks to me, triangulating on the blue capacitors visible through the holes in the board. There doesn't seem to be anything active there other than the transformer, so as you said earlier in this thread somewhere, the transformer is suspect.

[PlainBill]

Re: Samsung SyncMaster T240 - 2 seconds then black problem

I think that it was a fluke leaving half the inverter unplugged worked on the Sharp TV.

As for the brown spot, isn't that in the same position as the brown mark on one side of the transformer on the other side of the board? In your marked up picture of the other side it is just below the "'A; connector" label. At least, that's the way it looks to me, triangulating on the blue capacitors visible through the holes in the board. There doesn't seem to be anything active there other than the transformer, so as you said earlier in this thread somewhere, the transformer is suspect.

The transformer is definitely a suspect, but it appears the dark spot coincides with the jumper! A lot of these transformers are actually two transformers in a single package. I'd definitely try resoldering the jumper as the first step!

PlainBill

[mathog]

Re: Samsung SyncMaster T240 - 2 seconds then black problem

The ideal would be to apply the mythical "cheap and effective CCFL testing circuit" directly to the lamps, and so take the inverter completely out of the equation. Unfortunately said circuit has not yet been spotted on these forums.

For the other half of the equation, would one of these be OK for a dummy load? The 20W part shouldn't overheat even if the voltage is a bit too high, and they are less than $5 each.

http://search.digikey.com/scripts/Dk...e=HLWB-100K-ND

I keep trying to think of a really cheap and clever 100K load that could be put together from whatever one would have about the house. The only thing I have been able to come up with so far is a bucket of lightly salted water, in which is submerged a board with two nails through it, one test lead to each nail. The resistance could be adjusted to 100K by adding salt (titrating down from distilled water if the tap water conducts too much). The water could handle the heat produced, as long as the test wasn't run forever. But wiring hundreds of volts into an open container of conducting fluid just seems like an accident waiting to happen.

[mathog]

Re: Samsung SyncMaster T240 - 2 seconds then black problem

The transformer is definitely a suspect, but it appears the dark spot coincides with the jumper!

The jumper is probably an innocent bystander. It looks thick enough to handle the expected currents without heating up enough to darken the board. Hard to tell from the pictures, but it looks like the transformer might have blown smoke, or maybe even an arc, out along the general direction of the core. Since there were apparently previous repairs, it might have been the previous transformer that occupied that position which did this.

[PlainBill]

Re: Samsung SyncMaster T240 - 2 seconds then black problem

For the other half of the equation, would one of these be OK for a dummy load? The 20W part shouldn't overheat even if the voltage is a bit too high, and they are less than $5 each.

http://search.digikey.com/scripts/Dk...e=HLWB-100K-ND

I keep trying to think of a really cheap and clever 100K load that could be put together from whatever one would have about the house. The only thing I have been able to come up with so far is a bucket of lightly salted water, in which is submerged a board with two nails through it, one test lead to each nail. The resistance could be adjusted to 100K by adding salt (titrating down from distilled water if the tap water conducts too much). The water could handle the heat produced, as long as the test wasn't run forever. But wiring hundreds of volts into an open container of conducting fluid just seems like an accident waiting to happen.

I think the 20 watt rating is overkill. Do the math. The current of most CCFLs is in the 4-6 ma range. 600 volts, 100K ohm, 6 ma, 3.6 watts. Also, if I recall correctly, Wizard suggested 120 K ohm.

I'd think PPC120KW-3JCT-ND would do the job.

PlainBill