Dell 1703fps backlight problem

[mu2]

I have a Dell 1703 fps where the backlight turns on for about a second. Turning the monitor off and on again causes the light to repeat the cycle.
The monitor has a Lien Chang inverter board (LI-2070) and the power board is numbered BN41-00296B. I've replace 3 1000 mf 25v Capxon and 3 1000 mf 16v Capxon electrolytics on the power board. The caps showed no signs of bulging and also tested good with an esr meter. There are two other caps on the power board and one on the inverter board that check good (with esr meter) that I have not replaced.
If I monitor pins 1 and 12 on the connector going to the inverter board (I'm pretty sure this is supposed to be the 12 volt line) I get 17.70 volts when plugged in but not turned on - after turning on and the backlight comes up the voltage is 15.26. The backlight goes off and the voltage increases to 19.47 volts.
Seems like this backlight issue is common for this monitor - anyone have a fix for it?

Thanks

Mike

[PlainBill]

Re: Dell 1703fps backlight problem

I have a Dell 1703 fps where the backlight turns on for about a second. Turning the monitor off and on again causes the light to repeat the cycle.
The monitor has a Lien Chang inverter board (LI-2070) and the power board is numbered BN41-00296B. I've replace 3 1000 mf 25v Capxon and 3 1000 mf 16v Capxon electrolytics on the power board. The caps showed no signs of bulging and also tested good with an esr meter. There are two other caps on the power board and one on the inverter board that check good (with esr meter) that I have not replaced.
If I monitor pins 1 and 12 on the connector going to the inverter board (I'm pretty sure this is supposed to be the 12 volt line) I get 17.70 volts when plugged in but not turned on - after turning on and the backlight comes up the voltage is 15.26. The backlight goes off and the voltage increases to 19.47 volts.
Seems like this backlight issue is common for this monitor - anyone have a fix for it?

Thanks

Mike

Post good quality pictures of the boards. I'm not familiar with that monitor. The symptom you describe (often refered to as the 'two seconds to black' problem) has several causes. It can be a problem with either the inverter or the backlights (CCFLs).

PlainBill

[mu2]

Re: Dell 1703fps backlight problem

I'll work on getting some photos over the weekend, if my digital camera is still working.
Does the fact that the 12 volt input is high have any significance? Could the inverter be shutting down due to a too high voltage condition?

Mike

[PlainBill]

Re: Dell 1703fps backlight problem

I'll work on getting some photos over the weekend, if my digital camera is still working.
Does the fact that the 12 volt input is high have any significance? Could the inverter be shutting down due to a too high voltage condition?

Mike

It could be. Most inverter controllers monitor the output voltage and current and shut down if either go out of limits. But that raises other questions - what is the voltage supposed to be? (Not all inverters use a 12V supply). What is the voltage going to the logic board? Is it correct?

PlainBill

[mu2]

Re: Dell 1703fps backlight problem

My information on the 12 volt input came from this link.
http://www.lcdparts.net/InverterDeta...ProductID=2233
My inverter board (the Lien Chang LI-2070) doesn't look like this one although the CCFL connectors, inverter transformers and input connector are the same.
Since this is supposed to be a sub and 12 volts is mentioned as the input voltage, I figured my supply voltage was high. There is a KA431LZ which is supposed to be a programmable shunt regulator on the power board, but I haven't looked at the voltages in that area. Not sure if the 12 volts comes from there.

Mike

[mu2]

Re: Dell 1703fps backlight problem

Here is a photo of the power and inverter boards. I found that a connector on the power card is marked "14v" and "5v". My 5 volt supply is pretty close (5.1) but the 14 volt supply is high.

Mike

[Dgtech]

Re: Dell 1703fps backlight problem

I just bought this same exact monitor and it has the same exact problem. The power board is the same as above. It had 3 X 1000uF 25V and 3 X1000uF 16V. Recapped to all six new 1000uF 25V caps. Same problem exists still. I have yet to go through the checklist of "2 seconds to black" procedure. Has anyone ever found a solution to this problem with this monitor?

[retiredcaps]

Re: Dell 1703fps backlight problem

I just bought this same exact monitor and it has the same exact problem.

One case was traced to bad a CCFL post #16.

https://www.badcaps.net/forum/showth...t=Dell+1703fps

[hoadle]

Re: Dell 1703fps backlight problem

I work on Dell 1703 fps the problem you had is Lien Chang inverter board (LI-2070), take close look on bottom hight volt transformer on both side on hight volt transformer is burn up need replace (one side had 6 legs & another had 2 legs got to backlight)
check is out website last time I paid $39.95 + shipping or send you inveter they can repair
http://www.lcdpart.com/Products/li2070.html

[hoadle]

Re: Dell 1703fps backlight problem

Here another website & cheap too
http://www.lcdrepair.us/1703fps-inverter.html

[Dgtech]

Re: Dell 1703fps backlight problem

Wow, only $30? lol Just kidding. Thats way too much for a board that will repair a monitor that I bought for $20. I just went ahead and scrapped that monitor for a good pair of test CCFL's. Oh and other parts too.

[hoadle]

Re: Dell 1703fps backlight problem

I sorry to hear that, last time I had to buy ist & only one website sale cheap. You can save the Lien Chang inverter board (LI-2070) for future use, because only one hightvolt transformer go bad (they had 2 hightvolt transformer) you can use good hightvolt transformer to replace another board on Dell 1703fps.

[hoadle]

Re: Dell 1703fps backlight problem

Or you can find inverter transformer on ebay, to replace bad one

[Rtech]

Re: Dell 1703fps backlight problem

I understand the same Inverter is also used in the following units,so perhaps some of them may yield you a spare transaformrt,if you can find a 'scrapper' monitor.
Compaq

TFT1701

17" TFT Panel


Dell

1703FPS

17" LCD Monitor


Dell

1703FP

17" LCD Monitor


Dell

1702FP

17" LCD Monitor


Dell

1701FP

17" LCD Monitor


Dell

1900FP

19" LCD Monitor


Dell

E171FP

17" LCD Monitor


IBM

6657-HG2

17" LCD Monitor


Samsung

SyncMaster 171P

17" LCD Monitor


Samsung

SyncMaster 171B

17" LCD Monitor


Samsung

SyncMaster 181T

18.1" LCD Monitor


Samsung

LTM170E04-L01

17" TFT Panel


Samsung

SyncMaster 192MP

19" LCD Monitor

[bullwinkle]

Re: Dell 1703fps backlight problem

have a same dell model and same problem.

[sabre504]

Re: Dell 1703fps backlight problem

Had this problem to but took an inverter transformer off a dell 172
difference being that these are thro hole and the 1703 uses surface mount
but trimmed right they do fit but a deft bit of soldering required unless you are lucky enough to have a hot air station
not the prettiest of jobs but works the only real greif is removing the black glue from the transformer (hard as concrete)

[uligli]

Re: Dell 1703fps backlight problem

I have two 1703FPs, 2 secs to black symptom, both of them have Li-2070, with a burned transformer on each, took out a SIC1803 inverter from a 1702FP, and did fix the problem.

Those transformers have some tough plastic glue really difficult to disolder.

[Dgtech]

Re: Dell 1703fps backlight problem

Dude, very nice pics. Great job. That will indeed help people. As for myself, I now hate Dell monitors more than Samsung.

[sabre504]

Re: Dell 1703fps backlight problem

Strange that the transformer that has burnt out on the firt pic is the exact same one that i had to change be interesting to hear from others if the transformer is the one that has gone on theirs not that it probably makes a lot of difference but its the one closest to the psu board

[truckerron]

Re: Dell 1703fps backlight problem

i have the same monitor and same problem but don't know nothing about fixing eletronics where could i take it or send to get fixed thanks ron