benq fp91g+ (q9t4) monitor not turn on

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paulmars

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benq fp91g+ (q9t4) monitor. Mostly wont turn on. Once in awhile it does and works fine. However, that's very seldom. The on off switch hot side is 3.3vdc. The switch grounds that when its
pressed and my dvm then reads 0vdc. Every time. Ive traced it to the display circuit board plug, gray wire. So, it goes from 3.3vdc to 0vdc when the switch is pressed - Every time. Over and over
I can do this and every once in awhile, the unit powers up and it works fine. however, the next time, it wont power up.

Any ideas what could be wrong? All the caps look fine. Ive also inspected all solder joints.

tks,
pa
 


Check the power supply there may be a dried capacitor and instead of pure dc you may have pulsating dc in another words you may have ripples going to the micro controller the best thing to do is add another capacitor to get better filtration it might work, or check the clock to the micro-controller it may be un-stable.
 

3rd try replying. what is wrong with this forum. please post my reply.

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ok, this site is a joke. I replied and poof after submitting my reply its gone. I did it a 2nd time and poof its gone too. then I replied above, and it posts. so where the F is my original 2 relevant replies????? I stated that i checked the caps and asked how do i check that clock/controller? i wonder is this will post.
 

Check the 3.3 vdc with an oscilloscope to see it is clean and not pulsating, many microprocessors work with 3.3 vdc but the range usually is 3.0 to 3.6 vdc and if the filtering is poor of the 3.3 vdc it might be going below 3.0 vdc and it won't work. As you said that it works sometimes, that leads me to believe that some caps may have dried-up. With regular volt-meter you will read 3.3 vdc.
 

I was trying to find the schematic for the above model and found this instead. **broken link removed**

This is the power supply board, some one is selling it may be worth while to get and install it and your problem might go away.

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I was trying to find the schematic for the above model and found this instead. http://www.dhgate.com/store/product/genuine-power-supply-board-monitor-benq-fp91g/14200045-140156430.html

This is the power supply board, some one is selling it may be worth while to get and install it and your problem might go away.

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I have found the schematic for the similar model but I don't know how to up-load.


This is it, if up-load succeeds.
 
Prime suspects would be R608/R609 going high in value or C606/C611 going low in value. Measure the resistors out of circuit and change the capacitors anyway. Note they are low ESR types and rated to 105C temperature.

Brian.
 

thanks, I checking all these latest leads. Tks much. Too bad I only see posts when i log on to this page. it is set to notify me vie email, but it only did that once. Now i need to check myself everyday. I was out all sunday.
 

hmmmm. I tried that and I cant read it on screen or printed.

tks anyway.

pa

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hmmmm. I tried that and I cant read it on screen or printed.

tks anyway.

pa
 

Testing subscription notification 1

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Testing subscription notification 1

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Testing subscription notification 2
 

Hi paulmars
benq fp91g+ (q9t4)[schematic]
 

Attachments

  • BENQ Q9T4- FP91G.rar
    1.2 MB · Views: 165

how do i read an *.rar file?

I can read the schematic now.

my setting are set to be notified of posts to this thread. However, that is not happening.
 

This is compressed file, use winrar to unzip to a specified directory and than read it. It is also called extract.

paulmars said:
how do i read an *.rar file?

I can read the schematic now.

my setting are set to be notified of posts to this thread. However, that is not happening.
Click to expand...
 

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