HP w20 LCD Display Inverter, running out of options.

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  • deni-m
    replied
    Re: HP w20 LCD Display Inverter, running out of options.

    Originally posted by budm
    See picture for the B+ for the LED driver board.
    You still need to locate the BL_ON signal and the Dimming signal to control your LED backlights.
    Thanks for your post. Tomorrow I'm have free time to fix the screen.
    Just tell me is it necessary to remove the mosfet's?
    Isn't BRI mean brightness (dimming signal control),
    and ON/OFF its bl_on signal?
    Is it BRI first or second pin?

    Thanks again
    Attached Files

    Leave a comment:


  • budm
    replied
    Re: HP w20 LCD Display Inverter, running out of options.

    See picture for the B+ for the LED driver board.
    You still need to locate the BL_ON signal and the Dimming signal to control your LED backlights.
    Attached Files

    Leave a comment:


  • Agent24
    replied
    Re: HP w20 LCD Display Inverter, running out of options.

    Honestly if you're going the the trouble, you might as well just use new CCFLs.

    Considering the amount of LED backlight failures in cheap TVs these days, I don't have much faith in LED strips.
    LED strips have multiple LEDs. Each one is a point of failure. A single CCFL is much more reliable.

    Leave a comment:


  • deni-m
    replied
    Re: HP w20 LCD Display Inverter, running out of options.

    Hello,

    I need help. I'm want to update my hp w2007v from ccfl to led.
    I've already buy the led stripes and led drivers.
    Can somebody help me where to find 12V for drivers on this board.
    If need any info please tell me.
    Pictures attached.

    Thanks
    Attached Files

    Leave a comment:


  • sivads
    replied
    Re: HP w20 LCD Display Inverter, running out of options.

    Originally posted by CapBlown
    It's L106. Some sort of choke perhaps?
    test

    Leave a comment:


  • blackbox
    replied
    Re: HP w20 LCD Display Inverter, running out of options.

    Thank you for answering, selldoor. I paid for my impatience and for not reading carefully. Now I'm not living in the mainland and there are not many possibilities to find the 3KV caps. In the first page of this thread there is an explanation of the case with these caps but I decided not to wait and anxiously bridged C19 and C25 with the hope that something will change. It changed ... but for bad
    So I got what I deserved. Later I will try to investigate the problem and will communicate. Thank you.

    Leave a comment:


  • selldoor
    replied
    Re: HP w20 LCD Display Inverter, running out of options.

    Hmm read the thread some complex circuit stuff in there. More simple things I can help with. Did you test the secondary windings on the inverter transformers. Have you anything else you can check the bulbs on?

    Leave a comment:


  • blackbox
    replied
    Re: HP w20 LCD Display Inverter, running out of options.

    Hello guys, it's time for me to ask for help with this monitor. I read the thread and thanks to PlainBill and CapBlown I got my display working again. Previously it had the same problem like the CapBlown's but there was a smell like burnt. And the cause of this was the capacitor C17 (27pF/3KV) shown on the picture - it changed it's color to dark brown. The red line is the connection to the transformer.
    I removed Q23 and voila the backlight turned on. It worked some 4-5 days (10 hours a day) and started to smell again. Then I decided to put the two bridges (C19 and C25). When I switched the display on there was no backlight. I heared the high frequency noise for a while and then nothing.
    One important thing - I haven't changed any part on the board.
    Well, I will try to repair it. Thank you.
    Attached Files

    Leave a comment:


  • CapBlown
    replied
    Re: HP w20 LCD Display Inverter, running out of options.

    Update: This monitor has been working now for more than 750 backlight hours withour any problems since it was fixed. Strange that by removing parts you can actually fix something

    Leave a comment:


  • PlainBill
    replied
    Re: HP w20 LCD Display Inverter, running out of options.

    Originally posted by CapBlown
    Thank you for your advices and encouragement PlainBill. I've learned a lot within last few months.

    Removing Q23 seems to have solved this backlight shutdown issue for now. I just don't feel too good about it. Looking REV 3 board without that component I think I can live with it.

    I managed to destroy Q23 while removing it, so there is no going back anymore.

    It's great that this monitor is working again, but I have to admit that I am disappointed that I could not understand or locate the real reason causing this problem. Though I can always comfort myself thinking that there must have been a problem with the original design, why else would they have removed that Q23 from the next revision.
    I'm glad you have it working, too. Like you, I'd rather have understood exactly the reason for the problem. In general, there are two reasons for a new revision. In many cases it's to accommodate revised performance of one of the components. In the case of an inverter, to allow use of a different panel with different CCFLs. Sometimes it's to correct a design defect. I assumed the first reason; it may be that the design tolerances were too tight.

    PlainBill

    Leave a comment:


  • retiredcaps
    replied
    Re: HP w20 LCD Display Inverter, running out of options.

    Originally posted by CapBlown
    Thank you for your advices and encouragement PlainBill. I've learned a lot within last few months.
    Good job in getting this monitor working again.

    I think this thread and the "Acer AL2423W Recapped" by Per Hansson demonstrate the patience and persistance in troubleshooting the "tough dogs".

    I, for one, will have to re-read both these threads a few more times in the future for everything to sink in.

    Like smason wrote in another thread, I enjoy the detailed explanations and have lots more to learn.

    Leave a comment:


  • CapBlown
    replied
    Re: HP w20 LCD Display Inverter, running out of options.

    Thank you for your advices and encouragement PlainBill. I've learned a lot within last few months.

    Removing Q23 seems to have solved this backlight shutdown issue for now. I just don't feel too good about it. Looking REV 3 board without that component I think I can live with it.

    I managed to destroy Q23 while removing it, so there is no going back anymore.

    It's great that this monitor is working again, but I have to admit that I am disappointed that I could not understand or locate the real reason causing this problem. Though I can always comfort myself thinking that there must have been a problem with the original design, why else would they have removed that Q23 from the next revision.
    Last edited by CapBlown; 08-20-2010, 02:08 PM.

    Leave a comment:


  • PlainBill
    replied
    Re: HP w20 LCD Display Inverter, running out of options.

    Originally posted by CapBlown
    I got replacement cap for fragmented one. I purchased MMC with capacitance measurement capability and found out it was 98 nF so I replaced it with 100nF

    I measured also IC pin 13 (CT). I don't know if it means anything but if I measure it with multimeter, backlights immediately go off and AC voltage goes like this:
    1,8 V~ -> 9.9 V~
    Seems pretty sensitive circuitry... even though in this situation monitor can be switched back on immediately.



    I was wondering would it be worth trying to get rid off Q23. If that is the part which screws VSENS input signals, removing it like it's been done on REV 3 board might help?
    Try it.

    PlainBill

    Leave a comment:


  • CapBlown
    replied
    Re: HP w20 LCD Display Inverter, running out of options.

    I got replacement cap for fragmented one. I purchased MMC with capacitance measurement capability and found out it was 98 nF so I replaced it with 100nF

    I measured also IC pin 13 (CT). I don't know if it means anything but if I measure it with multimeter, backlights immediately go off and AC voltage goes like this:
    1,8 V~ -> 9.9 V~
    Seems pretty sensitive circuitry... even though in this situation monitor can be switched back on immediately.

    Originally posted by PlainBill
    You bring up a very good point. Q22 appears to be SMD code RKM; Q23 certainly is. That is a RK7002 MOSFET. Because of the way it is wired, it certainly changes the voltage on the OVP input of the controller. Because of the tests you did with jumpers we know that reducing the voltage on the Vsens input will prevent shutdown.
    PlainBill
    I was wondering would it be worth trying to get rid off Q23. If that is the part which screws VSENS input signals, removing it like it's been done on REV 3 board might help?

    Leave a comment:


  • CapBlown
    replied
    Re: HP w20 LCD Display Inverter, running out of options.

    Thanks again PlainBill.

    I think that eventually I will have a junk box . As a beginner I need to go shopping again. This time I'll get some extra components though, I never seem to have what it takes to do anything.

    Leave a comment:


  • PlainBill
    replied
    Re: HP w20 LCD Display Inverter, running out of options.

    Originally posted by CapBlown
    It's connected to pin 7, OVP, parallel with that 100kΩ
    Try something in the range of 1 - 10 nanoFarads. If you have a junk box with through hole ceramic caps, experiment. It shouldn't be critical.

    PlainBill

    Leave a comment:


  • CapBlown
    replied
    Re: HP w20 LCD Display Inverter, running out of options.

    Originally posted by PlainBill
    It's going to be difficult to determine the value. The first step would be to determine which pins on the IC it is hooked to. There are several timing caps that set delay times. If this is one of those, it will be fairly easy to select a 'common' value.

    PlainBill
    It's connected to pin 7, OVP, parallel with that 100kΩ

    Leave a comment:


  • PlainBill
    replied
    Re: HP w20 LCD Display Inverter, running out of options.

    It's going to be difficult to determine the value. The first step would be to determine which pins on the IC it is hooked to. There are several timing caps that set delay times. If this is one of those, it will be fairly easy to select a 'common' value.

    PlainBill

    Leave a comment:


  • CapBlown
    replied
    Re: HP w20 LCD Display Inverter, running out of options.

    I was watching some old pictures and it looks like that cap was looking allright when I got this monitor. It must have gone like that during testings or when resoldering it.

    Leave a comment:


  • CapBlown
    replied
    Re: HP w20 LCD Display Inverter, running out of options.

    Thanks PlainBill.

    Thinking about that OVP input I took a closer look at it. Makes me wonder if I've found a bad capasitor. At least it looks like there are fractures in it so I think I better change it. How could I identify it's capasitance as I have no schematics.
    Attached Files

    Leave a comment:

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