Question about ViewSonic Optiquest Q7b Flat panel TFT 17" Monitor

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Optiquest q20wb Screen goes blank after powering off

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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  • johnkr May 01, 2009

    I have the same problem of the screen going blank. I also took the monitor apart and found a large hole in the insulating sheet between the power supply and the metal case to which it's mounted.

    The power supply seems to be dead. Anyone know where I can get a new one?


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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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I had same problem , pulled out a old mobo and stole the 470uf 10v 105 deg. c cap {is the smallest one on the power supply board} replaced and it worked fine and now i am trying to mount a exhaust fan over the area where the caps are, i noticed the most heat damage there browning of the board start with the 470uf 10v and work your way down im shure that will work=-)

Posted on Jun 06, 2009

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SOURCE: Optiquest q20wb Screen goes blank after powering on

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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Posted on Jan 02, 2017

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