Benq G2255 doesn't power on - amber power light when plugged in

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  • will62
    replied
    Re: Benq G2255 doesn't power on - amber power light when plugged in

    OK. We doubled the delay, and it still failed. Do you have any 1N4148 diodes? Would need 2. If not, you're going to need to pull that B6 diode off the other board and check it. Is it a common anode dual? Should test just like the diode D801. If so, go ahead and try it. It's under valued, so it may fail, but we need to rule out the diode.
    Last edited by will62; 01-25-2018, 09:56 PM.

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  • rddube
    replied
    Re: Benq G2255 doesn't power on - amber power light when plugged in

    Ok Will, found one that was 2.33uf, so I tried it. Now the lamps turn on for about 5 seconds before going out. Jumpered on C803, they stay on nice and bright.

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  • rddube
    replied
    Re: Benq G2255 doesn't power on - amber power light when plugged in

    Ok, resoldered evrything and measure pin 2 and 3 to ground.

    Pin 2: 2.403Kohms
    Pin 3: 2.406Kohms

    Now did partially the other operation to remove C803 and checked the value with my Fluke and transistor tester.

    With the Fluke I get: 1.027uf
    With the transistor tester I get 1030nf

    I guess this is the same thing. As a replacement I found a 2.15uf and a 6.14uf...the 2.15uf is 2X the value and the 6.14uf is 6 times the value. Which one should I use Will?
    Last edited by rddube; 01-25-2018, 08:55 PM.

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  • will62
    replied
    Re: Benq G2255 doesn't power on - amber power light when plugged in

    Ok, solder pins back down. Get me that resistance to ground for each pin (2,3).
    Let's try extending the time the chip gives before faulting. Remove C803. Measure it's value. Try to find a replacement on another board with ~3 times the value. Remember, if you have to, you can parallel 2 and add their values.

    example: If you measure it as 820nf, try to find a replacement in the range of 2.5uf.

    After changing cap(s), turn on with and without pin 5 jumped.

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  • rddube
    replied
    Re: Benq G2255 doesn't power on - amber power light when plugged in

    Ok, so resoldered pin 3, lifted pin 2, jumpered to pin 3. CLF in original position. First time I flip the power bar switch, I got a quick flash from the CFL's then black. Waited approximately 1 minute, then when turned on they stayed on.

    Swapped the connectors. Exactly the same thing. First time I switched the AC on, got a quick flash from the CFL's then black. Waited approximately 1 minute, turned them on and they stayed on.

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  • rddube
    replied
    Re: Benq G2255 doesn't power on - amber power light when plugged in

    Ok, Will. Just to let you know however, I tried it again after about 10 minutes (pin 3 up) and CFL in original slots, and they came on and 2 seconds they were out. Waited about 45 minutes before coming to see if you had replied, so went to the board to move on to pin 2 lifted. Before dismantling it, tried it again, the came on and stayed on!

    Ok, moving to pin 2 now.

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  • will62
    replied
    Re: Benq G2255 doesn't power on - amber power light when plugged in

    Move on to pin 2 lifted.

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  • rddube
    replied
    Re: Benq G2255 doesn't power on - amber power light when plugged in

    Originally posted by Dumah Brazorf
    My experience is that i had to change lamps that look good the few seconds they was working but was worn/burned at the ends.
    You can only open that panel, it's not hard but tedious. Changing the cfl desoldering the old and resoldering the new in the manner that fits inside the panel instead is a pain in the arse...
    Hi Dumah,

    Tks for the info. I would really like to avoid having to change the lamps, because I don't have any spares and also, there is a problem on the main board that I haven't tackled yet, trying to get the power board to work. If you look at Budm's previous post, he show a way you can test the board with scrap CFL lamps which is pretty neat. I'll have to see what Will thinks (and Budm) before contemplating changing/testing the lamps.

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  • rddube
    replied
    Re: Benq G2255 doesn't power on - amber power light when plugged in

    Will, I am getting weird results. Still with pin 3 lifted and jumped to pin 2. When CFL's inverted, they come on and turn off after a few seconds. I did the test 3 times, same results.

    Swapped the CFL's, first test they wouldn't come on, so I thought maybe I have to wait a little for the chip to reset. Tried it after a few minutes, wouldn't come on. So I checked my jumper and the AC plug and tried it again, and this time they came on, but out after a few seconds. Waited approx. 2 minutes, they came on and out after 2 seconds. Waited about 5 minutes, this time they came on and stayed on. Turned them off, waited another 2-3 minutes, they came on and stayed on.

    It's as if the problem is intermittent? What should I do now?

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  • Dumah Brazorf
    replied
    Re: Benq G2255 doesn't power on - amber power light when plugged in

    My experience is that i had to change lamps that look good the few seconds they was working but was worn/burned at the ends.
    You can only open that panel, it's not hard but tedious. Changing the cfl desoldering the old and resoldering the new in the manner that fits inside the panel instead is a pain in the arse...
    Last edited by Dumah Brazorf; 01-25-2018, 02:39 PM.

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  • will62
    replied
    Re: Benq G2255 doesn't power on - amber power light when plugged in

    Yes, redo pin 2 as well. We need to be sure on this. Once you finish and resolder both down, please measure resistance to ground for both.

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  • rddube
    replied
    Re: Benq G2255 doesn't power on - amber power light when plugged in

    Ok Will, I'll do that before anything else. So you want me to redo the test with pin 2 lifted also again (pin 3 back in its place), sort of a double check just in case I might have missed something in the first test?

    Tks.
    Last edited by rddube; 01-25-2018, 01:33 PM.

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  • will62
    replied
    Re: Benq G2255 doesn't power on - amber power light when plugged in

    While you have the jumper between p2&3, please confirm what I said in post #174.

    Pin 3 lifted - Both lamps come on and stay on ONLY when lamp connectors are in normal position. Invert connectors, and both lamps come on, but go off in a couple of seconds.

    Pin 2 lifted - Both lamps come on and stay on, regardless of how the connectors are attached.

    Need to nail this down before moving on. Then you can put the pins down, remove jumper and recheck the waves. Don't forget to also check them by probing at voltage divider (before diode... reread post#169)
    Last edited by will62; 01-25-2018, 10:42 AM.

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  • rddube
    replied
    Re: Benq G2255 doesn't power on - amber power light when plugged in

    Hey Budm,

    I have a few of these lights, do you think I could use them without having to open them?

    They are sold at home depot for 4.97$

    Tks!
    Attached Files

    Leave a comment:


  • rddube
    replied
    Re: Benq G2255 doesn't power on - amber power light when plugged in

    Hello Gentlement,

    Sorry for my late reply, had an emergency last night which kept me away from my bench. Will resume testing tonight.

    Will: Ok will be probing again pin 2 and pin 3 to repeat results. I presume I put pin 3 back in it's place and remove the bridge with pin 2?

    Budm: The test with one lamp connected, do you want me to do it while the chip is bridged (i.e. pin 3 is lifted right now, connected to pin 2) or do I put everything back in it's place before testing the one lamp at a time? And tks for the link on verifying power supply/inverter board.

    Leave a comment:


  • budm
    replied
    Re: Benq G2255 doesn't power on - amber power light when plugged in

    Originally posted by rddube
    Ok Will, did the test. When CFL's plugged in original position, they turn on and stay on. When reversed, they turn on and turn off after about 2 seconds.
    That made no logical sense to me.
    If you have just one lamp connected one at time, does get the connected lamp to flash on for seconds and go black?
    I use this to verify the power supply/inverter board: https://www.badcaps.net/forum/showthread.php?t=19987
    Last edited by budm; 01-24-2018, 09:32 PM.

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  • will62
    replied
    Re: Benq G2255 doesn't power on - amber power light when plugged in

    The fact that the lamps came on with only pin 2's input going into pin 2 & 3, tells us that there is nothing wrong with the pin 2-cn801 circuit by itself. It's the difference between the 2 inputs that is causing the shut down. I didn't expect the lamps to go off when the plugs are inverted though. That points towards a bad lamp. They worked both ways when you lifted pin 2, but with pin 3 lifted, they only work one way (normal connection). I'm going to have to think about that.

    Can you go back to post #169 and answer that 2nd paragraph about the first pic. Was the negative swing on pin 2 a fluke? Please check that out again, and try the others in that paragraph.
    Last edited by will62; 01-24-2018, 09:30 PM.

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  • rddube
    replied
    Re: Benq G2255 doesn't power on - amber power light when plugged in

    Ok Will, did the test. When CFL's plugged in original position, they turn on and stay on. When reversed, they turn on and turn off after about 2 seconds.

    Leave a comment:


  • will62
    replied
    Re: Benq G2255 doesn't power on - amber power light when plugged in

    That's great about the original mosfet, one less variable to consider. Still wondering why the lamps came on with the under rated mosfet. Is it blown? If you haven't started already, I'd jump ahead to the lifting of pin 3. That might tell us that there is not an over-current problem.
    Last edited by will62; 01-24-2018, 04:15 PM.

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  • rddube
    replied
    Re: Benq G2255 doesn't power on - amber power light when plugged in

    Originally posted by will62
    Another thing that I was wondering about, is when you first changed the mosfet to the under rated AF4910N that you had on hand, you said the lamps came on for about 10 seconds. Now that you know how to properly check a mosfet, are the original AP9962 and the AF4910N actually blown?
    Hi Will,

    Took you up on this comment and I checked the AP9962AGM (I had kept it) and guess what, you're quite right. It was not blown at all, just me not measuring it properly off the board. So, I removed the other one and placed this one back and tested - exact same results...CLF's light up and go off after 2 seconds. If I install my alligator clip on C803, they light up and stay lit.

    So, I'm off to do the other tests...should I start with the probing of the pins, maybe try to get a better scope image (yours is a nice square wave and you can see the spike very well)...or should I try the resistor up and measure milliamps?

    Leave a comment:

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