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Old 07-31-2011, 04:28 PM   #1
gapi
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Default Samsung 215TW Testing Questions

Hi Guys, I have searched and read but I am not a seasoned technician but do have a Fluke multi-meter and can solder fairly.

I have two displays both being the non REV.02 powered units.

I want to state my symptoms and ask a couple if I can.

The display turns on for a second and blackens out. I replaced all the caps and they were not bulged. I have done this operation on another display having bulged caps with success. What next?

Another display that flickered and blacked out I changed the caps and it seemed fine until I went to adjust it. The brightness was almost maxed so I dimmed it and the left side went darker and she blacked out. I cycle power and it shows for a second only. I cannot get at it to brighten it but why if its bad right?

As for the transformers?? Can the be tested on board or do the need to be removed?

Thanks, any help would be great.
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Old 07-31-2011, 04:56 PM   #2
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Default Re: Samsung 215TW Testing Questions

Quote:
Originally Posted by gapi View Post
Hi Guys, I have searched and read but I am not a seasoned technician but do have a Fluke multi-meter and can solder fairly.

I have two displays both being the non REV.02 powered units.

I want to state my symptoms and ask a couple if I can.

The display turns on for a second and blackens out. I replaced all the caps and they were not bulged. I have done this operation on another display having bulged caps with success. What next?

Another display that flickered and blacked out I changed the caps and it seemed fine until I went to adjust it. The brightness was almost maxed so I dimmed it and the left side went darker and she blacked out. I cycle power and it shows for a second only. I cannot get at it to brighten it but why if its bad right?

As for the transformers?? Can the be tested on board or do the need to be removed?

Thanks, any help would be great.
The problem you describe is usually referred to as 'two seconds to black. There are four likely causes - bad caps, bad CCFLs or wiring to the CCFLs, bad inverter transformers, and a bad component in the sense circuitry. You have eliminated the first likely cause.

The transformers can be tested while still on the board, of course with power off. Measure the resistance of the secondaries of each transformer. They should match to within 3%. If you are not certain about which pins are for the secondaries, post pictures of the top and bottom of your power supply / inverter. PLEASE use 'Manage Attachments' - below the text entry area.

Substituting known good CCFLs (it is not necessary to remove them or the originals from a panel) one at a time can help locate the problem CCFL or wiring.

PlainBill
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Old 07-31-2011, 09:07 PM   #3
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Default Re: Samsung 215TW Testing Questions

Thanks,

Attached are pics of a duplicate board that hums. Also note the caps in between the transformers are supposed to be 13mm in Dia but the supplier sent me 10mm. Problem?

Also a closeup shot of some discoloration on the boards bottom.

I did not post the actual board because its still assembled but it is the same part number.
The purpose here is hopes for you to help me with the test pins locations, and to show you a second board and ask about the 10mm vs. 13mm.

Let me know if if the pics are ok and if you need to look at the actual board. Thanks!
Attached Images
File Type: jpg BN44-00127B_FRONT.jpg (208.8 KB, 20 views)
File Type: jpg BN44-00127B_REAR.jpg (360.2 KB, 12 views)
File Type: jpg BN44-00127B_REAR_MARKS.jpg (194.2 KB, 13 views)
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Old 07-31-2011, 09:29 PM   #4
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Default Re: Samsung 215TW Testing Questions

Quote:
Originally Posted by gapi View Post
Thanks,

Attached are pics of a duplicate board that hums. Also note the caps in between the transformers are supposed to be 13mm in Dia but the supplier sent me 10mm. Problem?

Also a closeup shot of some discoloration on the boards bottom.

I did not post the actual board because its still assembled but it is the same part number.
The purpose here is hopes for you to help me with the test pins locations, and to show you a second board and ask about the 10mm vs. 13mm.

Let me know if if the pics are ok and if you need to look at the actual board. Thanks!
I've placed a yellow dot on each end of the secondary. It appears that all six transformers have one end of the secondary tied to the same point, probably ground. The other end is covered in insulation. I'd suggest just probing the pin in the connector.

The critical parameters on replacement caps include capacity - exact match is important, voltage - don't go lower, ESR (impedance at 100Khz) - don't go higher - and physical size - you must be able to get the covers on. A smaller diameter should not be a problem provided the other parameters are met.

PlainBill
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File Type: jpg Samsung 215TW Power Supply bottom-1.jpg (400.7 KB, 11 views)
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Old 07-31-2011, 10:23 PM   #5
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Default Re: Samsung 215TW Testing Questions

Fantastic, I'll check them out.

While waiting for you I did some trouble shooting by swapping parts. I have two of these I am trying to make one out of I hope or better.

What I ended up with is:
  • One panel thatseems to have no back light.
  • A power supply board that hums
  • A working panel of sorts that when dimmed below 100% brightness the left side goes dark and then she goes black. If I play around with the buttons and cycle power I can get her back up but if I mess with brightness or take it into a custom setting she'll go dark. I swapped logic boards also and there is no change. I think I need some cfl testing instructions too.

Fun stuff. I'll checking the transformers and perhaps await a link to checking my lamps?

Thanks!
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Old 08-01-2011, 06:38 AM   #6
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Default Re: Samsung 215TW Testing Questions

Far and away the best way to test CCFLs is by substitution. Fortunately, most CCFLs use the same pinout. One part of my test kit is a CCFL assembly removed from a monitor. By using that to replace each CCFL in turn, I can identify a defective CCFL without opening the LCD panel. One Unique guy here also modified a power supply / inverter so he can test CCFLs directly.

Each of these are tools. In your case, I would use the inverter / power supply and signal card from the monitor with brightness issues to test the other panel.
And vice versa.

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