I have a Dell E172fpb 17" lcd manufactured by BenQ. It will not power on, the power button justs blinks green and the screen flashes. I have taken the panel apart and examined the power inverter board. There are no bulging capacitors, but it is full of Lelon caps. I have seen on this forum that this brand is considered one of the least desireable. Anyone have any experience with this LCD panel or problem? I have done several other capacitor repairs, but always the sure tail sign(bulging).
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Re: Dell E172fpb
Originally posted by syclonejimI have a Dell E172fpb 17" lcd manufactured by BenQ. It will not power on, the power button justs blinks green and the screen flashes. I have taken the panel apart and examined the power inverter board. There are no bulging capacitors, but it is full of Lelon caps. I have seen on this forum that this brand is considered one of the least desireable. Anyone have any experience with this LCD panel or problem? I have done several other capacitor repairs, but always the sure tail sign(bulging).
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Re: Dell E172fpb
This board was a little bit confusing at first to determine which connectors are not at mains potential. CN701 (and CN753) are safe to measure, because there appears to be a blank area of PCB between it and the primary side.
The first area to make measurements is CN701 (low voltage power supply). Also measure the output on diodes D751 and D761. Take care when measuring CN752 and CN753. You may need to measure voltage between each pin of these connectors, instead of GND.My first choice in quality Japanese electrolytics is Nippon Chemi-Con, which has been in business since 1931... the quality of electronics is dependent on the quality of the electrolytics.
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Re: Dell E172fpb
Symptoms...
If the monitor is connected to a PC (in windows or whatever), when you first power it up, you get a very quick flash of the windows desktop on the display. The power LED then starts flashing at a rate of around 1 flash per second.
I have taken voltage readings at CN701... Pins 9 & 10 pulse 3.3V, but as i'm using a Digital VM, it seems to fluctuate between 1.5 and 3.3V. Pins 7 & 8 pulse between approx 2 and 5.0V. Pins 3 - 6 are GND.
If you listen closely to the board, you can hear a "tick" when it pulses... my hearing is not great, so i can't pinpoint where the "tick" is coming from...
If anyone is interested, I've attached a pic of the under-side of the board.
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Re: Dell E172fpb
here is an interesting thread
http://www.network54.com/Forum/87612...9/DELL+E172FPB
regarding the caps, those elna style vents suggest koshin caps. i would be interested to know if they test off spec.
its hot in the region of the fets.....Last edited by willawake; 03-12-2006, 02:09 PM.
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Re: Dell E172fpb
on that thread i linked they had some fets going bad. but there has got to be a reason for that? badcaps running fets hot? or just bad design
i would sink them anyway once you get that up an running. looks kinda toasty there. edit : actually forget that some are sinked the others impossible.Last edited by willawake; 03-12-2006, 03:03 PM.
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Re: Dell E172fpb
Ok, on my board, the blue caps are brand new (maybe still crap, limited stockists nearby and not enough time to order over the net), labeled C751, C703, C712 C709, C707, C708 and C710.
D701 and D702 are UGF10DCT Diodes (with sinks).
Thanks for the link willawake... Looking at that, it looks like the same problem I have, so, does anyone know of a stockist in the UK that has some 2SC5707's (Edit: or equiv) (in lower quantities than 700)? Quick google didn't reveal much...
Thanks for all the help!Last edited by HelpQuick; 03-12-2006, 03:32 PM.
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Re: Dell E172fpb
I have the exact same monitor and as of tonight the same exact symptoms.
I pressed the power button and it broke. At this point the monitor started to flicker on and off once a second with the green light pulsing at the same time as well as a small click or chirp.
I took it appart and can not see any damage to the actual led or switch.. just the button is broken on the monitor face.
I can see no damage to the small board the led and switch is connect to.
Luckily I have someone here who is familiar with working with boards and they will take a look at it.
Thanks for the info.
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Re: Dell E172fpb
The monitor that i had fixed with the help of this forum has once again failed... this time, the monitor works for around 2 hours, then goes off with the original symptom.
If it's left off for a while, it can be used again for about 2 hours (presumably some sort of thermal problem)
I haven't had a chance to look at it again yet, but will let you know how i get on.
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