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Re: HP no backlight
Thanks retirecaps here are the results for the diodes D116 .948 - .547, D111 .546 - 0L D107 .842 - 0L, D 108 .537 - .696, D114 .549 - 0L, D103 .543 - 0567, D101 .543 - 0L, D120 .547 -.951, D121 .547 - .951, D118 .549 - 0L, D105 .547 - .573, D109 .543 - 0L, D112 .543 - 0L, D113 5.37-.696.
D 116, 108, 103, 120, 121, 105, & 113 look suspect and I have not removed them?? I am checking the transistors first and will report when complete.Comment
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Re: HP no backlight
Transistors Q101 S-G 0L S-D 20m G-D 0L Q109 S-G .98m S-D .92m G-D 4.62m Q107 EC 0L EB 99.2k CB 15.7m Q102 EC 29.5m EB 29.5m CB 0L Q103 EC 51K EB 31M CB 0L Q106 EC 99K EB 98K CB 197K Q108 SG .90m SD .90M GD 4.5m I have not removed the suspect ones and all test done as per your instructions post #19Comment
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Re: HP no backlight
I have taken Q101 of the board an it would appear that it is shorted. S-G 0L S-D .67m G-D 0L Q101 is a 2N7000 same as Q109. I don't have a replacement so I can't try itLast edited by davg; 11-09-2012, 11:44 AM.Comment
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Re: HP no backlight
Your readings would be a lot easier to read if they were like this
S-G - 0L
G-D - 0.5M
D-G - 0.7M
instead of everything on one line.--- begin sig file ---
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Re: HP no backlight
Thanks retiredcaps I can see what you mean so sorry. Hope the attachment is easier?Comment
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Re: HP no backlight
I notice that on some of your resistance readings for transistors, you use "M" versus "m". What's the difference?Comment
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Re: HP no backlight
Just a slip of the finger caplock on?? No difference. My meter is auto and most of the readings were megaohms? I just borrowed a fluke 87 lll from my son and some of the readings are different "not much" Am I correct in thinking that Q101 is shorted because I am not reading 30 ohms or is this normal? I believe Q101 may be a switching transister?? Would that make a difference to the reading?Comment
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Re: HP no backlight
If a reading is less than 30 ohms, then it is shorted.--- begin sig file ---
If you are new to this forum, we can help a lot more if you please post clear focused pictures (max resolution 2000x2000 and 2MB) of your boards using the manage attachments button so they are hosted here. Information and picture clarity compositions should look like this post.
We respectfully ask that you make some time and effort to read some of the guides available for basic troubleshooting. After you have read through them, then ask clarification questions or report your findings.
Please do not post inline and offsite as they slow down the loading of pages.
--- end sig file ---Comment
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Re: HP no backlight
Am I reading your chart wrong? For Q101, you're showing 0L, 0L and 20M. "0L" means "out of range". In other words, I don't see anything that reads less than 30 ohms, indicating a short.Comment
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Re: HP no backlight
Ha you are right what am I thinking and with Q101 removed the reading is
S-G - 0L
S-D - .67m
G-D - 0L
So I can re solder that back in and start over?? ShootComment
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Re: HP no backlight
Pin 7 is the big suspect right now since there is no any low resistance circuit connected to this pin at all (lestr was getting about 900K Ohms).
It can be c110 (.01uf) may be bad or internal IC at pin 7 is bad. Try removing C110 first, see if it is surface mounted or not? You can try lifting pin7 but that may be difficult to do.Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809Comment
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Re: HP no backlight
Thanks budm I am not sure I understand your request with respect to C110? C110 is not surface mounted and if I remove it do I try the board without it in place??Comment
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Re: HP no backlight
Cant second guess that but have been looking at the pics. I am not sure
which is pin 7 but if you start at bottom left or bottom right in the attached as pin1then can you check that pin6 and pin7 are not conducting at the solder joints.
Clean the flux off if it is only flux.Attached FilesPlease upload pictures using attachment function when ask for help on the repair
http://www.badcaps.net/forum/showthread.php?t=39740Comment
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Re: HP no backlight
Thanks Selldoor that is pin 6 & 7 it was some flux and I cleaned it up still no differenceComment
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Re: HP no backlight
There is something at pin 7 to make it show real low resistance (123 Ohms) at that pin, you can remove the cap C110 or lift pin 7 off the trace and measure the pin7 solder pad to see if you still get low resistance reading. We are trying to find out what is causing this low resistance reading since there is no component with that low value resistance connected to that pin7.Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809Comment
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Re: HP no backlight
Thanks budm with C110 removed pin 7 is still reading 123.9 ohms so should I try lifting pin 7?Comment
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this tv is throwing me for a loop. do samsung tvs no longer have the backlight self test feature built into the power supply?
i tested the backlight with my LED tester and it lights up both strips. one of them reads 100v and the other reads 63.7v.
unplugged mainboard from power supply but left backlight plugged in, and then plugged psu wall power in. expected to see backlights light up but see nothing.
according to how ive diagnosed in the past, this would almost always be a bad power supply. replacement power supply was cheap like 20$ from ebay. but still i get not even... -
I bought this p2210f dell monitor to fix. Schematic is the same as p2210.
Behaviour is that monitors comes on but then backlight switches off almost instantly. If I look with flashlight I can still find the "No signal message". So definitely a backlight issue. Trying to advance the issue I proved that the protection circuit is switching off the backlight by shorting out C3 and resistor to disable the INL chip then re enable by removing the short.
This is where it gets interesting. When I disassembled the monitor to solder leads on c3 capacitor I noticed the backlight flickered... -
Hello all,
Am trying to figure out this backlight issue with this A1990 Macbook Pro.
Tests performed:
There is no backlight even with a good screen.
Backlight IC is receiving the correct support voltages.
Fuse F8400 ok
Current sense resistor R8400 ok
Backlight IC is receiving 3.3V on enable pin.
Backlight IC receiving voltage from PPBUS_G3H, aprox 12.5V.
Backlight IC receiving 5V from PP5V_G3S
Backlight IC BKLT_SCL and BKLT_SDA both measure 0.545V diode mode to ground
I2C_BKLT_SCL and I2C_BKLT_SDA both measure... -
Hello, got an iPad Pro A2378 12.9 5th gen with no backlight. Got another test unit without screen, tested the screen, still no backlight with the test unit.
Figured out the backlight on the screen was bad, ordred a new backlight from mobilesentrix, *carefully replaced it* without damaging the lcd, oh well.
Final result, issue is still there, the screen has no back lights. So i'm back to square one, with 3 hours less and 100$ out, issue still on the screen.
The panel is still ok, i can see the apple in the middle of the screen when it kicks in, just no backlight.
Anyone... -
Hi all,
I've got an LG Flatron 24EN33TA with a backlight issue. The problem began with the monitor not powering up after sitting for a long time (overnight or during the day throughout work). When I would wake the computer up, the backlight would flick on for a second then go out. Sometimes it would take many tries to get it to come on. Once the monitor came on, it worked flawlessly until another long duration of being powered off.
I thought the problem would be bad caps but I checked both of the caps on the board and they are fine. I also tried powering the monitor from...
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