Samsung SyncMaster T240 - 2 seconds then black problem

[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

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

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

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

[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

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

[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

[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