Re: HP W2207 Backlight Problem
Correct. Some designs have the CCFLs in parallel, others have them in series with the current sense circuitry at the junction. This board uses the series design.
PlainBill
HP W2207 Backlight Problem
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Re: HP W2207 Backlight Problem
with the cheap capacitor tester I recently purchased
I had ordered some new CCFLs a while back so I rigged one up to connect to the board. Brand new CCFLS! I tried testing each board and the SAME problem showed up:
https://www.badcaps.net/forum/showpo...1&postcount=14Leave a comment:
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Re: HP W2207 Backlight Problem
Require that 2 CCFLs be installed, If only one CCFL is used the lamp will only light part of the way.
I would redo the test with all the CCFLs installedLeave a comment:
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Re: HP W2207 Backlight Problem
If your board is the same as in post #1, then go ahead and check U501 and U502 for shorts. What are their part numbers?Leave a comment:
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Re: HP W2207 Backlight Problem
Yes they all need to be installed
I would use 2 new in one tranformer and 2 old in the other,then switch every thing around if the second to black problem continues.Leave a comment:
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Re: HP W2207 Backlight Problem
No, only the one. Should I plug in all 4?Leave a comment:
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Re: HP W2207 Backlight Problem
^
When you're doing the testing you do have 4 CCFLs installed correct?Leave a comment:
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Re: HP W2207 Backlight Problem
Resurrecting this thread yet again!
Ok, so I picked up an inexpensive DMM that can measure at the 2k range. Here are my findings:
As per retiredcaps instructions here:
Linky
I measured the red circles:
.478
and the yellow circles:
.484
That looks to be within the 3% threshold.
Now, some more info. I have about 10 monitors I received since my company does recycling. All of the monitors have a 3 second to black problem. Of the three monitors I have so far opened, ALL THREE HAVE THE SAME POWER BOARD.
I replaced ALL the caps on the powerboard pictured above on my first post. None of the caps were distorted at all, and with the cheap capacitor tester I recently purchased (which could be crap, but here is a link) said that the caps were mostly in the correct range. Granted, it's not ESR and it doesn't rule much out, but I was able to replace all the caps anyway.
After reading many posts about this board (it's fairly common and the actual LCD manufacturer seems to be Samsung for these 3 monitors I opened up with the same problem) I decided to set up a test CCFL. I had ordered some new CCFLs a while back so I rigged one up to connect to the board. Brand new CCFLS! I tried testing each board and the SAME problem showed up:
When the board powers up, the CCFL lights up dully (not a full light up) for about 2 seconds then shuts off. I have tried this with 3 of the brand new lights to the same effect.
I will not let this thing beat me! Especially since I have 3 different boards, if I could even get ONE to work I would be happy. I have a feel it's a similar problem, and I have found others with the same board with the same symptoms and the fact that I have THREE of the SAME boards makes me want to fix this like crazy.
The next step:
I read somewhere that someone was having problems with the mosfet or something like that. Should I give that a test?
Thanks for all the help! I'll try to buy everyone a round of beers when/if I can fix this thing!Leave a comment:
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Re: HP W2207 Backlight Problem
I was in the hvac-talk.com forum and saw reference to your multimeter, Field Piece.
Looks like it is a fairly specialized meter and thus doesn't have the same ranges like electronic multimeters.Leave a comment:
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Re: HP W2207 Backlight Problem
Awesome! Thanks for the reply. I'll see if I can't find a meter with the 2000 range.Leave a comment:
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Re: HP W2207 Backlight Problem
Most secondary inverter transformer readings are around 1000 ohms or 1K. With your multimeter set to 200K, that would mean the reading should show up as 1 on the right hand side of the display. A reading of 1K will probably not be sufficient resolution to tell if your transformer is good or bad.
In order to do this test, you will need to borrow a multimeter that is autoranging or a manual one with a 2000 ohm range.
PS. Most manual range multimeters have ohms ranges of 200 ohms, 2k, 20k, 200k, 2M, and 20M. I can't recall seeing one like yours with such a wide gap in the ohms range. I suspect it was to allow the MFD range so they had to compromise.Leave a comment:
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Re: HP W2207 Backlight Problem
Sorry I keep dragging this out. It's been a while since I've been able work on this again. I'm attaching a picture of my multimeter in hopes that someone can tell me which setting to use. When I measured it using the circled settings shown in the picture I didn't get a very good reading.
Thanks if anyone can tell me what to set it to to measure the inverter.Leave a comment:
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Re: HP W2207 Backlight Problem
I just picked up one of these today. It has 2 bad CCFL's.If you need to compare any readings let me know.Leave a comment:
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Re: HP W2207 Backlight Problem
0.00 IS a reading on a resistance measurement. It means 'too low to measure'. OL or the equivalent (varies with the meter) is 'no connection', two vastly different things.
PlainBillLeave a comment:
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Re: HP W2207 Backlight Problem
Hey, sorry about the delay. I finally measured the ohms of the locations you highlighted. I have my device set to 200k and was unable to get ANY reading. I even tried 20M and only got 0.00 on both.Leave a comment:
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Re: HP W2207 Backlight Problem
Those rarely fail. Not never, but rarely. If your line voltage is 110/120 and not 230/240 then they are not subject to voltage stress anywhere near their limits, and they normally don't see huge heating.Leave a comment:
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Re: HP W2207 Backlight Problem
You should check your work with a known good single ccfl and rule out a bad install/wiring. That is, unplug one ccfl at a time and substitute the good one (you don't have to disassemble anything, just stretch the cable to the good ccfl).Leave a comment:
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Re: HP W2207 Backlight Problem
Go ahead and measure across the 2 pins (7 and 8) of each inverter transformer and report your findings.Leave a comment:
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Re: HP W2207 Backlight Problem
1) Put your multimeter on 2000 ohms (if manual). Power off and unplug the lcd. Wait 2 minutes.
2) Measure the 2 red dots. Report ohms.
3) Do the same for yellow dots.Last edited by retiredcaps; 02-07-2011, 04:05 PM.Leave a comment:
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