Did I kill the monitor

Discussion in 'General Electronics Chat' started by Gdrumm, Oct 17, 2014.

  1. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
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    It's a ProView 464 (or 483, or 400 something) monitor that someone threw away.
    I took it home and tried it out, and it worked, except for a slight red tinge.
    I tried adjusting it with the color button, but couldn't navigate the adjustment.
    After 4 attempts to download a Users Manual, I finally found a forum post that said it didn't work well with Windows Vista.

    In an unclear moment, it seemed to stop working, although the LED "ON" light was flashing.
    In frustration, I literally "pulled the plug", without disconnecting it from the PC first.
    The PC was still powered on.

    As I unplugged it, I saw a tiny spark at the 110 outlet, as the plug prongs were coming out.
    I'm guessing I fried something, because now it won't do anything.

    It has an AC Adapter, and I plan to test that later today.
    The PC still works fine, with another monitor.

    So my question is: "Did my haste in unplugging it while it was still hooked up to the PC cause it to crash?"
    I've repaired several flat screen monitors over the years, and I usually find bad capacitors.
    Would the action of unplugging it while it still hooked up to a live PC cause that?

    Thanks for reading.

    Gary
     
  2. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    No pulling the monitors "power plug" out of the outlet did not cause any problems...
    You said it "seemed to stop working" before you pulled the plug anyways.

    There is always a "spark" (voltage spike, etc...) when you disconnect any power circuit while "energized".. Electricity basically wants to stay connected.. The "arc" was the fingertips of the electricity jumping the air gap right before finally letting go
     
  3. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
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    Thanks for the feedback mcgyvr.
    Gary
     
  4. wayneh

    Expert

    Sep 9, 2010
    12,151
    3,058
    It may be bad form but I wouldn't expect that to destroy a monitor. After all, unplugging it would be identical to having the power go out or a breaker blow.

    I wonder about the quality of the interface connection, and perhaps a monitor setting that has become scrambled.
     
  5. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
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    I found the problem.
    The Power Supply that was with it when I picked it up is 24v DC, and the Monitor is 12v DC.
    (PS is Kodak, Monitor is ProView).

    They may have accidenally connected it to the PS of some Kodak device.
    I guess it was shutting down and they didn't relize it was connected to much higher voltage than required.

    I have several PS, I'll find the right one and give it another try.

    Thanks for the input.

    Gary
     
  6. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
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    I found two bad caps.
    One was 470 uf 16v, and I have a salvaged one in my box.

    The other was a 100 uf, 6.3 v........... all I have is 100 uf, 16v.

    Can I use that?
     
  7. shteii01

    AAC Fanatic!

    Feb 19, 2010
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    When I was replacing capacitor on power board of my lcd monitor, I found following advice and I followed it, I now have working lcd monitor:
    For replacements:
    - ESR should be the same or lower.
    - Ripple should be the same or higher.
    - Voltage should be the same or higher. [Without getting ridiculous.]
    - Don't wanna change uF unless you have to.
    - Also make sure it will physically fit both diameter and height.

    So far:
    - Your uF are good.
    - Your voltages are good.
    - You are missing: ESR, Ripple, Dimentions.
     
  8. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
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    No soap.
    I'll try again tomorrow.
    Pizzas here.

    Thanks
     
  9. Agent24

    Member

    Jun 14, 2010
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    But not excessively lower, some power supplies will become unstable or noisier if ESR is reduced too much.
     
  10. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
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    I'm testing the board mounted Power Jack Socket with my meter.
    I'm using the audible conductivity function.
    Pos. to pin, Neg. to socket wall).

    A weird thing is happening, when tested the pos. to neg., I get one beep, and then nothing.
    Likewise, when I do neg. to pos., I get one short beep, then nothing.

    When I do Pos. to Pos. I get a continual beeeeeeeeeeeeeeeep (like it should)
    and when I do Neg. to Neg. I get a continual beeeeeeeeeeeeeep. (like it should)

    Does the weird scenario mean that the board mounted Power Jack Socket has a short it it?

    Hope this make sense.

    Thanks
     
  11. Agent24

    Member

    Jun 14, 2010
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    Not sure what you mean when you say you tested "Positive to negative or Positive to Positive" etc.

    Positive of what to the negative of what? jack only has 2 pins, how you can have 4 different test cases?
     
  12. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
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    Sorry,
    Normally when I check for continuity, I put one meter lead on the pin, and one on the board where the pin is mounted, and if there is continuity, I get a long beep (thats good).

    Likewise, I can put one meter lead on the inside wall of the Power Jack Socket, and the other on the board, where that bit attaches, and I get a long beep (thats good).

    I then check one against the other (from the pin, to where the socket wall ataches to the board) to see if there is a short. Usually that produces no beep (no short, also good).

    In this case however, when I cross check them, I do get a very brief beep, and then if I detatch one lead, and touch it in the exact same place again, a second time, I get no beep.

    Does that sound like something normal?

    Maybe I found it.
    A Diode nearby is shorted out.
    I'll replace it if I have one, and post back.

    Thanks,
    Gary
     
    Last edited: Oct 22, 2014
  13. Agent24

    Member

    Jun 14, 2010
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    Ah,, I get it now.

    What you describe does sound normal - when you test across the jack pins, your tester voltage is charging up the filtering capacitors across the power rail. At the start they look like a short circuit, so you get a beep. As they charge they look like an increasing resistance and finally an open circuit when charged so the beep stops. Of course they don't discharge instantly, so when you test the 2nd time, there is no beep. If you reverse the probes you are discharging them and then charging them in the reverse polarity, so you get another beep.

    You can do a basic test of large capacitors (above say 100uF) this way with resistance scale - measure across the leads and watch the resistance increase (works better on analog meter). If you don't see increase, the increase is too fast, or the charge does not hold, the capacitor is probably bad. Of course such a test can not determine reduced capacitance, (except in severe cases) or test for ESR etc. But it can be a quick test to weed out really bad ones like shorted, high leakage, or open.


    From your first post, you said there was a red tinge to the image. That may have been from the too high voltage PSU messing with the image processing circuits, but it can also indicate old\dying backlights, which can also cause problems. You can replace these but it's a bit tricky. Not impossible though. Lamps are cheap on eBay.

    It would help if you could upload some photos of the boards etc, and get the exact model number.

    If it does not work at all now, suspect blown fuses, blown regulators etc from the overvoltage.
     
  14. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
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    Agent 24,

    Excellent feedback, and thank you.
    I should have time to work on it this weekend, and can post photos of the board, etc.

    Gary
     
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