Question about ViewSonic OptiQuest Monitor

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Optiquest q20wb Screen goes blank after powering on

The other day I turned the screen back on, the computer was still running, and I got my desktop for about 2 seconds then the screen goes blank. I've read previous post that were similar to this problem that stated the issue was in the power supply and the fix was to replace bulging capacitors. I pulled the power supply and found 3 - 25v 470 mF can style caps and 2 - 10v 1000mF can style cars. I replaced the 470's but this didn't solve the problem. I'm currently trying to hunt down the 1000's and see if this resolves the issue.

My question is; Has anybody had this problem on a q20wb and is someone might know if there is a possible transitor problem. How could/would I check this?

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  • formulacoop Mar 04, 2009

    I bought the monitor new about 2 years ago from Newegg. It was purchased for personel use so it was only turned on on the weekends. I would say it has less hours on it than my Acer 19" I have at work that works fine. So I don't believe this monitor has been over user or run its course.

    There are only a screen, power supply and power/OSD controls for this monitor. The inverter may be built into the power supply. It looks pretty close to one of these but just slightly different;



    http://www2.shopjimmy.com/showmonitorpar...



    I went ahead and replaced the capacitors mentioned due to previous comments made in other posts regarding this issue. I did tested the capacitors I removed with my Fluke 88 DMM and they tested good to me. None of the capacitors appear to bulge but I have also been told they don't neccesarily have to bulge to be bad. I'm just not sure how to test some of these components but I know it has to be something simple. Any other ideas would be greatly appreciated.

  • formulacoop May 06, 2009

    Thanks for all your suggestions. I did however managed to figure out the problem. The issue was identified in the power section.



    Thanks again



  • daron_uk May 11, 2010

    Hi I have the same monitor with the same problem. I have changed the 2 x 1000mf 10V caps and the single 470mf 10v but still no fix. Can you tell me how you fixed your monitor? Thanks

  • Oblivion
    Oblivion May 11, 2010

    "The issue was identified in the power section."



    In other words... It was the fuse and you don't want to admit it :-)

    LOL just kidding, Even if it was. It happens to the best of us. I once worked on a TV for three days just to find out that one socket in the surge protector I was using was burned out -.-



    Ahhhh... good times

  • Lou Ebert May 11, 2010

    formulacoop, Don't keep it a secret. Tell us what was wrong!!! Was it a WEEVIL infestation that you sprayed with RAID bug killer?? Did you need to take the power board to car wash to clean off the dried soda-pop residue? Is everything OK now? louie12fix on fixya

  • Oblivion
    Oblivion May 11, 2010

    This may seam child’s play, but have you covered *ALL* the basics properly? Things like trying different power cords and computers, checking fuses with a continuity meter as opposed to just checking by eye? ect. ect.



    If so, pat your self on the back as most people pass over these "formalities" in an attempt to get the problem fixed faster.



    Now that that’s out of the way, answer me this. Do the lights on the bottom (like the power light.. if it has one) still come on?



    If NOT then the problem may not be in the inverter but rather in the main power area its self. And if so then I would put money on the switching FET of the SMPS being blown. Incase you don't know the switching FET is a black thing with 3~5 leads attached to a heat sink in the HV/mains area of the circuit. The area will have the power socket and be surrounded by a "trace-free-mote" of sorts.



    As for testing caps with a standard $5 ohmmeter. Set it to less than 1000K ohms (or on the continuity setting.) A good cap will conduct (short) for a while (like a second) then slowly stop (open). If the meter never gets close to infinity, (more than around 500k ohm's) then the cap is likely blown. Of course a cap can pass this test and still be bad. But if it fails it is most likely dead. Bulged caps will almost always PASS this test, but still be bad so I guess it doesn't really help you out much.



    An other EASY way to test a capacitor is to hook it to a 9V battery for a second. Then hook it to a small light and count how long it takes to discharge. I just tested this theory for you with a 2200ohm resister (red-red-red-gold) and a standard 5mm red LED and a good 1000uF cap took a bought 9~14 seconds to get mostly dimmed out. And a 470uF cap took 5~7 seconds as expected. Your actual test results may vary do to component tolerances and part choices (if you choose to do this at all) (LED color DOES make a diffrence)



    I'll get back to you as needed -Oblivion



    P.S. I have caps that I MAY be able to mail you if its absolutely necessary. But any radio shack should have what you need.

  • Lou Ebert May 11, 2010

    formulacoop, If you are not sure how to use digital multimeter ( DVM-DMM) your best shot would be to ask a local TV tech if he could look for any SHORTED JUNCTIONS on the driver and output semiconductors (transistors) that pulse the small transformers that are on the inverter board. You should also verify that the inverter board is receiving it's own 12volts from the other pwr supply board. Also look at the bottom of the Printed circuit for what is called " COLD SOLDER JOINTS" and rework if necessary. It might be benificial for you to find an old 20 - 30x microscope to look at them. Now if you have only 2 boards in your monitor then chances are you have a COMBO supply. If there are 3 boards then you most likely have a seperate inverter board. Now here is a web site that deals with replacement inverter boards that you may want to check out. www. slectronics.net/NEC-LCD/monpart.htm Oh! one more thing. If replacing Capacitors. Always use the 105 deg. C capacitors. Do not use cheap 85 deg C Did you have anyone check with a meter to verify that the removed ( pulled) capacitors were in fact bad? Had lost 40-60% of their capacitance?? When you post a message on something that has failed try to estimate the age of the product or how many hours of use the device has on it. I hope that some of this helped out. I'm louie12fix on fixya or lmistyrel @ aol.com

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I'd like to report a success story. I had this same problem with my Q20WB. It sat for over a year in my garage. I eventually bought replacement capacitors, soldered them in, and now it works. You can find kits with the right capacitors preselected, or if you feel like it you can also buy them individually.

good luck

Posted on Feb 25, 2011

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SOURCE: Optiquest q20wb Screen goes blank after powering off

I had the exact same problem. The screen went black and the green light flashed. I went ahead and took the monitor apart (scary) and took a look at the power supply circuitry. I saw 6 suspicious electrolytic caps on the board. Three 470uF 25V 105 degree C caps, two 1000uF 10V 105 degree C caps, and one 470uF 10V 105 degree cap. They all appeared to be slightly bulging and one even had a small hole in the top. I decided to replace all of them. The parts cost a little more than 5 bucks. I couldn't find a 470uF 10V cap at my local store so I bought a 16 V version instead, which is fine. Anyway, after replacing all 6 caps, the monitor works as good as new.

Posted on Jul 15, 2010

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