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Dell 17 inch LCD repair

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golemmaster

New Member
I have two Dell 17 inch LCD screens that are not working.
They have similar power supplys in them. Typical BenQ innards.

One has an open fuse and four bad transistors that I'm about to replace. Power LED stays stead on. Hopefully that's it for that one.

The other one has a good fuse and transistors. The power LED flashes. I can hear ticking from the high power section. The LED flashes in time with the ticking. Voltage in the low power section pulses with the ticking.

I'll post a pic when I find my camera.


What to check.....
I have a decent multi-meter. I don't have an ESR meter. Love to have one.


Thanks
 

creakndale

New Member
I repaired a 19" Samsung SyncMaster 920N that had the same ticking/blinking LED issue. One of the P-Channel Mosfets on the CCFL inverter hybrid circuit board shorted out (drain to source). This caused a high current "shoot through" condition.

I suggest monitoring the 12V feeding the inverter with your multimeter. With the Samsung, each "tick" would momentarily short out the 12V power supply.

I initially replaced an electrolytic capacitor that was bulging and had leaked a little hoping that was the problem. Unfortunately, that didn't solve the problem so I had to dig deeper and eventually found the shorted Mosfet.

Ordered a replacement component from DigiKey.

creakndale
 
Last edited:

HiTech

Well-Known Member
At the least visually inspect CLOSELY, the CCFL's inverter transformer for signs of heat, abnormal discoloration to the windings. Often the Xformer gets taken out with the inverter semiconductors.
 

golemmaster

New Member
Dell E172PFb and E173PFb

Dell E172PFb and E173PFb
See attachments.

I've removed the Q743 and Q751 D10PFT06 on one model, FU9024N on the other. Best I can tell they may all be bad.
The Q739, Q740 and Q759, Q760 C5707 seem to be good on one monitor and bad on the other. The fuse is bad on one monitor. I've checked R765 and C765 that control the frequency of the oscillator circuit in IC751. Best I can tell they are within tolerances.

Waiting for parts and time and knowledge.
 

Attachments

smith_mario

New Member
Dell E152FPB Lcd Screen is Blank

Dear There,
Dell E152FPB Lcd Screen is Blank
Please see my Dell LCD condition in
WELCOME

How I can repair my Dell LCD
Regards
 

golemmaster

New Member
Dell E172PFb and E173PFb

I replaced the C5707 and ST D10PF06 MOSFETS and fuse.
Backlights work but no video. No "No Signal" box that would normally be displayed. The monitor doesn't go to sleep. I know I've read about this symptom somewhere but can't remember where and of what to suspect and test next.

Although the fuse on one of the monitors tests good on the DMM, it seems to die when I turn the monitor on. Measuring directly off the legs of the fuse:
Voltage ahead of the fuse 18.5VDC. 19.5+VDC behind the fuse. (strange)
When I push the button: ahead remains 18.5VDC, behind the fuse quickly dives to about 4VDC. Voltage returns to 19.5VDC behind the fuse when I shut the monitor off. This results in a flicker of light from the backlights. I temporarily shorted the fuse leads together and the back lights turn on. Didn't check video function on that one yet.
 

golemmaster

New Member
Dell E172PFb and E173PFb

I spoke too soon. One of the screens works fine. FIXED! :D

The other with the weird fuse.... that works but does that odd thing previously mentioned. I shorted the fuse and that monitor is working too. I need to fix that and I'll be all done. Shweet :p

I'm also working on a BEFSR41 router.... but that's another thread.
...And my AMP/Receiver. Too complicated for me but I'm poking around in it anyway.
 
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