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tofutofu Guest
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Posted: Sun Jan 22, 2012 12:16 am Post subject: BenQ FP547 15" BLACK SCREEN |
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hello everyone.
trying to found the problem in the Q5x3 power board of my benq FP547 monitor.
the problem started with black screen every few minutes . but soon become black permanent.
conecting to power and a signal, giving a green light (recognize the signal).
i changed 2 puffed cap's. with no chang.
checking the voltage on bord:
the V-inverter is 13.3v (is that OK?). but no power is geting in to the 2 small transformers (cant see any Voltage after the fu9024n mosfet-[ Q751 and Q743 on the diagram]) .
I changed the 2 couple of transistors [Q759,Q760 & Q730,Q740 on diagram] (should be 2SC5706. but I got only the 2SC5707 that was available at store ) and replaced the 2 fu9024n mosfet. but no chang.
I'm working with the diagram, but don't have any clue what to do next.
any help or idea?
the diagram URL:
elektrotanya.com/benq_q5x3-304_power-bd_acer-547.pdf/download.html |
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jts1957
Joined: 24 Nov 2008 Posts: 2476 Location: Far, Far Away
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Posted: Sun Jan 22, 2012 1:24 am Post subject: |
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Replace FP751 and resolder all terminals of T751 & T752. _________________ You're over there, I'm over here. |
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tofutofu Guest
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Posted: Sun Jan 22, 2012 6:58 am Post subject: need to וnderstend |
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jts1957 wrote: | Replace FP751 and resolder all terminals of T751 & T752. |
thanks for your replay.
but the voltage after the fuse (pf571) is good (13.33v)...
should I replace it anyway?
does T751=Q751?
thanks |
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tofutofu Guest
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Posted: Sun Jan 22, 2012 7:33 am Post subject: more data |
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the BLT_on voltage :
1)when starting, (no connection to vga source)- the green light is turning on for few seconds and the voltage is 3.3v as well (and then go to 0.0v)
2)when connection to vga source- the green light is turning on permanent- voltage is 0.0v
is that all-right? |
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jts1957
Joined: 24 Nov 2008 Posts: 2476 Location: Far, Far Away
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Posted: Sun Jan 22, 2012 8:36 am Post subject: |
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Yes
T= Transformer
Q= Transistor
FP= Fuse _________________ You're over there, I'm over here. |
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tofutofu Guest
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Posted: Sun Jan 22, 2012 10:54 am Post subject: more data |
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tanks JTS1957, I will try that.
I just found out that when starting, (no connection to vga source)- the green light is turning on for few seconds and the voltage is 3.3v as well (and then go to 0.0v). then, the back-light is turning on for few seconds. with the message "NO SOURCE" on screen.
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tofutofu Guest
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Posted: Mon Jan 23, 2012 2:24 pm Post subject: |
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I i told before, I can see the back light turn on for few second
does that means the inverter is good? |
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jts1957
Joined: 24 Nov 2008 Posts: 2476 Location: Far, Far Away
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Posted: Mon Jan 23, 2012 3:47 pm Post subject: |
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Try connecting one CCFL bulb at a time and see if each lights for a couple of seconds. _________________ You're over there, I'm over here. |
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tpfutpfu Guest
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Posted: Tue Jan 24, 2012 12:39 am Post subject: |
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jts1957 wrote: | Try connecting one CCFL bulb at a time and see if each lights for a couple of seconds. |
tried that. both bulb are working separately for few seconds.
the BLT_ON voltage drop from 3.3v to 0.0v when the back light turned off (also when connected to VGA source)
I tried connecting 3.3v to the BLT_ON from other source. the back-light is turning on, then I can see the picture blinking on the screen every second (wile the back light is continually turned on).
anything to do from hear? |
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jts1957
Joined: 24 Nov 2008 Posts: 2476 Location: Far, Far Away
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Posted: Tue Jan 24, 2012 1:00 am Post subject: |
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There should be FOUR bulbs - two top, two bottom. Since both bulbs on top (or bottom) share a holder, you must test them individually.
BLT_ON (backlights ON, active when LOW) - Backlights turn on for a couple of seconds ... what happens to the 3.3v/0volts? _________________ You're over there, I'm over here. |
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