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dvorav
Member
Last Activity: 04-17-2010, 04:16 AM
Joined: 10-07-2008
Location: Czech Republic, Europe
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  • dvorav
    replied to BELINEA 10 20 05 no picture, confused
    in Troubleshooting Computer Displays
    Re: BELINEA 10 20 05 no picture, confused



    Never mind. It can happen to anyone.

    Talking about bad caps, I have always thought, that caps are degrading in continuous way. This case is most likely sudden death....

    Anyway, I'll probably give up this case... it is too much complicated... too much time and effort and still nothing.

    Thanks for all posts....
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  • dvorav
    replied to BELINEA 10 20 05 no picture, confused
    in Troubleshooting Computer Displays
    Re: BELINEA 10 20 05 no picture, confused



    Those caps on inverter board are:

    4 pieces of NICON, 56 uF, 25 V, 105°, F204C EVL, green

    Few posts before I have written this about voltages on PSU output (to inverter board):

    Connector:

    Bright. (37 mV*) | GND (0 V) | VO (12 V) | VO (12 V)
    -------------------------------------------------
    ON/OFF (4,15 V) | GND (0 V) | GND (0 V) | VO (12 V)

    Bright. 37mV with disconnected LCD panel. ON/OFF (4,15 V) with monitor turned on (green LED shining)....
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  • dvorav
    replied to BELINEA 10 20 05 no picture, confused
    in Troubleshooting Computer Displays
    Re: BELINEA 10 20 05 no picture, confused



    In fact it took around 2 sec, as you mentioned. Thus protection is obviously working.



    Well, according to the pictures of inverter board, caps (all 4 of them) seem all right.
    When you mentioned MOSFET... i have realized that presumption of working mosfet (which is always overheating after several secs) can be wrong. I'll try to measure the voltage and maybe even to measure the MOSFET to see if it isn't shorted. Then I'll give the report.

    Thanks...
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  • dvorav
    replied to BELINEA 10 20 05 no picture, confused
    in Troubleshooting Computer Displays
    Re: BELINEA 10 20 05 no picture, confused



    Hi.

    A strange thing is that inverter will shut down after protecting paint around mosfet starts smoking due to extensive overheating of that part. I mean if any lamp is defective I suppose that the inverter should shut down immediately, not after the overheating the mosfet. (I don't know how long it takes to inverter shut down due to CCFL defect.)

    As well as I don't know what to do with protective circuits, which were mentioned two posts before. I haven't worked with them before.
    ...
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  • dvorav
    replied to BELINEA 10 20 05 no picture, confused
    in Troubleshooting Computer Displays
    Re: BELINEA 10 20 05 no picture, confused

    Hi to everyone,

    after some time I carried out some tests with CCFLs. I disconnected one branch (with frying transistor) and then I turned it on (with external variable power supply). Remaining CCFL blinked on and off. No activity after that. Surprisingly the same result. CCFL blinked on and off. If both CCFL are bad, why would be only one transistor frying?
    Any ideas what to check next?

    dvorav
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  • dvorav
    replied to BELINEA 10 20 05 no picture, confused
    in Troubleshooting Computer Displays
    Re: BELINEA 10 20 05 no picture, confused



    They blinked on, then off. Is any procedure to measure bad transformer? Yesterday I have measured resistance between legs of both transformer primary circuits. They had both the same values about 0.2 Ohm. There should be some noise when the transformer is arcing, am I right?

    May I try to unplug the branch of CCFL, where the transistor is frying and to test the current drain?...
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  • dvorav
    replied to BELINEA 10 20 05 no picture, confused
    in Troubleshooting Computer Displays
    Re: BELINEA 10 20 05 no picture, confused

    Hi community!

    Here are the promised result from the measurement.

    I desoldered both fuses and soldered a pair of wires instead. I have used a variable power supply with maximal current of 6 A. Firstly I tried to slowly increase the voltage to 12 V and to monitor the current at the same time. The voltage was set up to approx. 8 V with current 4 A. When increasing the voltage the current rose over 5A. The lamps went on for short while (picture was ok, signal board is all right), then they went off, but at the same...
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  • dvorav
    replied to BELINEA 10 20 05 no picture, confused
    in Troubleshooting Computer Displays
    Re: BELINEA 10 20 05 no picture, confused


    Nice material, that's for sure. Some things are clearer after reading this.

    Yes, the value of fuses will be challenge. But as a clue, I think, can be used max current specifications on power board (central board). There are some specifications next to the black connector.

    Model A (ticked)
    VO1: 12V/1.8A
    VO2: 12V/2.8A

    Right side of fuses is powered by 2 VO's , thus at worst we have 2*2.8A. Probable value of fuses can be over 3A. But I agree, for first its safer to try only...
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  • dvorav
    replied to BELINEA 10 20 05 no picture, confused
    in Troubleshooting Computer Displays
    Re: BELINEA 10 20 05 no picture, confused

    Hi Bill, thanks a lot for advising.

    I tried both approaches; precisely according to your definition. Here are the acquired data.
    The first one (measuring voltage from both sides to ground) gave following readings.
    F1 – left side to ground – 0 Volts
    F1 – right side to ground – 12 Volts
    F2 – left side to ground – 0 Volts
    F2 – right side to ground – 12 Volts
    The second one – measuring resistance from left sides to ground showed that circuit is open. (Neglecting the...
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  • dvorav
    replied to BELINEA 10 20 05 no picture, confused
    in Troubleshooting Computer Displays
    Re: BELINEA 10 20 05 no picture, confused

    I have measured those components F1 and F2. Are they really fuses? If yes, they are blown open (DVM showing open circuit, of course I have removed isolating resin film) despite they do not have any obvious marks of being fried. What it a cause of opened fuses?

    F1 is the upper one from view of the inverter.jpg. Component F2 is the lower one. They both are bearing number 63. I don't know what for type of fuse is it.

    What next?
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  • dvorav
    replied to BELINEA 10 20 05 no picture, confused
    in Troubleshooting Computer Displays
    Re: BELINEA 10 20 05 no picture, confused

    First of all, thank you for posting your reply.



    You mean F1 - the main fuse? If yes then it has 0.1 Ohm. Maybe I'm blind but I can't find it. There are another two fuses F501 and F503, both having 0.1 Ohm. I think they work fine.


    I have measured that connector:

    Bright. (37 mV*) | GND (0 V) | VO (12 V) | VO (12 V)
    -------------------------------------------------
    ON/OFF (4,15 V) | GND (0 V) | GND (0 V) | VO (12 V)

    Bright. 37mV with disconnected...
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  • dvorav
    started a topic BELINEA 10 20 05 no picture, confused
    in Troubleshooting Computer Displays

    BELINEA 10 20 05 no picture, confused

    Greetings everyone!

    I have got Belinea 10 20 05 20" LCD monitor recently. It's not functional. When you plug it in (without signal cable) and turn it on, it doesn't display anything (not logo nor missing signal table, which is commonly displayed when you plug monitor without signal cable) but power LED is green. After a while (usually around half minute) power LED goes amber.

    Thus I opened it finding 3 swollen caps (on fig 3 marked by red arrows). Photos of untraditional 3 board agraggate are attached. After recapping, nothing changed; monitor is not working...
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    Last edited by dvorav; 04-27-2009, 02:00 PM.
  • dvorav
    replied to HP L1702 goes on and off
    in Troubleshooting Computer Displays
    Re: HP L1702 goes on and off

    Yes, the monitor all goes off. And it couldn't be turned on for a while (unless you unplug it and pug it in again with some delay). Seems strange.
    And also that buzzing noise, can't determine right direction, but it seem it is going from PSU board (maybe even from the small green board on it).
    Any clues?
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  • dvorav
    replied to HP L1702 goes on and off
    in Troubleshooting Computer Displays
    Re: HP L1702 goes on and off

    Hi to all,

    I got one HP 1702 recently. It has a similar problem. After switching it on, there is picture for lets say 1-2 sec, with outgoing such a scratchy sound. Then it goes off (power LED is not shining).
    I measured around 310V on main capacitor. But when disconnecting it, it stays charged for a long time (tents of minutes). So I measured starting resistors. They are two and have 0.6M Ohm in series. It seems good.
    The rest of capacitors looks fine, none swollen or so. (They are KZE green ones).

    Any ideas...
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  • dvorav
    replied to Samsung SyncMaster 720N - power LED blinks
    in Troubleshooting Computer Displays
    Re: Samsung SyncMaster 720N - power LED blinks

    Thanks for patience with me. I have great regard for it.

    I have taken some pictures of the Video Board. All caps are Su'scons. Although they are in good visual state, they may be faulty. Complete list and placement of the caps is attached.

    Is there chance, that the problem is in faulty caps?...
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    Last edited by dvorav; 03-13-2009, 01:45 PM.

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  • dvorav
    replied to Samsung SyncMaster 720N - power LED blinks
    in Troubleshooting Computer Displays
    Re: Samsung SyncMaster 720N - power LED blinks



    Thanks for explanation.

    If I understand it right, PSU giving 3.21V. Thus signal board evaluates the PSU signal as faulty and then turns the PSU and itself off.

    I'm testing it on my PC from where I'm actually writing. VGA was connected to running secondary monitor - I used it as a source....
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  • dvorav
    replied to Samsung SyncMaster 720N - power LED blinks
    in Troubleshooting Computer Displays
    Re: Samsung SyncMaster 720N - power LED blinks

    to: Scenic There aren't any components radiating extraordinary heat. But the caps may be bad. I'll try to exchange them.
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  • dvorav
    replied to Samsung SyncMaster 720N - power LED blinks
    in Troubleshooting Computer Displays
    Re: Samsung SyncMaster 720N - power LED blinks



    Thanks for remark.

    I have realised I wasn't right. I'm running that monitor on 230V AC so reading 346V or so is meaningfull.

    Edit: to: PlainBill Exactly Europe....
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    Last edited by dvorav; 03-13-2009, 10:28 AM.

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  • dvorav
    replied to Samsung SyncMaster 720N - power LED blinks
    in Troubleshooting Computer Displays
    Re: Samsung SyncMaster 720N - power LED blinks

    Well - I got it now (too slow ) but if output voltage from PSU isn't stable - it must be the PSU. But where is the source of that problem?
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  • dvorav
    replied to Samsung SyncMaster 720N - power LED blinks
    in Troubleshooting Computer Displays
    Re: Samsung SyncMaster 720N - power LED blinks



    Fitst of all, thanks for contributing.

    1) When VGA cable connected, I was possible to turn it on (power LED was shining). Then I measured 3.21V between 5 & 6. After while the LED started blinking. I measured the 5 & 6 again obtaining 0.02V (almost zero). That's the problem.
    Voltage measured between 6 & 1 was 5.08 - I suppose that is ok.

    2) I was confused how to measure that big cap. I measured AC between legs and ground (now I know it wasn't proper) resulting in around...
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