Dell 1704FP LCD w/pwr but 2 secs to Dark

[lestr]

I'm a noobie who has been successful in fixing a few LCD's with standard through-hole components, but this 1704FP LCD has quite a few SMD's, something I had not tinkered with before. It all started with a no power indication. Opened up the case and found power supply components to be ok, resoldered in places that looked marginal, and replaced the shorted four FET's in the top-side of the inverter section. Powering up the board by itself, I got the following voltages at the output diodes (mounted on heat sinks): 5.3v, 12.7v, and 20.0v. At the connector P802 with the wires that connects the main board: pins 1-3, 5.3v; 4-7, 0v (grd), 8-10, 0v. With such encouraging results, I reconnected everything and repowered to get the power led to light up and for a few seconds show the OSB on the screen. By examining of the underside of the board where the SMD's are found, resistors are easy to identify but condensers are not marked. I was also able to read the markings on the following three SMD components which I don't have details for:

On the inverter side of the board,
I801: SG6841SZ, KMA233305490g
On the power supply side,
I101: OZ9930g, S1090122T, 0S46A
Q804: 13N06L

Markings on the Power-Inverter board: 6832151100-02, PTB-1511, 8/19/05.

Without a schematic and very little information on this model, it's hard to make much progress. The problem still seems to be in the inverter. Another burning question: are SMD components fairly easy to get and remove/install? Your insights and help to resolve this problem will be
much appreciated. Thank you.

[budm]

Re: Dell 1704FP LCD w/pwr but 2 secs to Dark

You may want to read this first:
https://www.badcaps.net/forum/showthread.php?t=10419
Check the resistance reading of the transformers. No bad caps, bad cap can look normal but will have high ESR. May be bad lamp assemblies.
http://s807.photobucket.com/albums/y...ell%201704FPT/
Bad lamps:
http://s807.photobucket.com/albums/y...klight%20lamp/
Inverter tester lamp:
http://s807.photobucket.com/albums/y...g%20old%20CFL/

SG6841SZ is SMPS IC

OZ9930 PWM IC Pinout, see pciture/pdf

[lestr]

Re: Dell 1704FP LCD w/pwr but 2 secs to Dark

Thanks budm for the links, pictures, and info on the components. I have a lot to read and study. The inverter tester lamp really got my eye and the thing to try. I will post my findings as progress is made.
By the way, I found out that 13N06L is a Logic N-channel FET, rated 60v, and that there is also an N-channel FET with the number 13N06. I wonder what a logic fet is and what purpose it serves in the power board?

[budm]

Re: Dell 1704FP LCD w/pwr but 2 secs to Dark

Can you take the resistance reading on all the pins of the OZ9930 with ref to ground (black probe on the chassis).

[smason]

Re: Dell 1704FP LCD w/pwr but 2 secs to Dark

Seems to me I have one or two of this model on my shelf waiting for transformers.
It's a fairly common problem on this model.

[Lumberjack777]

Re: Dell 1704FP LCD w/pwr but 2 secs to Dark

Seems to me I have one or two of this model on my shelf waiting for transformers.
It's a fairly common problem on this model.

Hey smason. Isn't this the same board used in the Dell 1905FP and Dell 1704FPt where they used the wrong capacitor near the transformer? The manufacturer missed a decimal point and they used a 22uF 50v where it should have been a 2.2uF 50v and it took out the transformer?
https://www.badcaps.net/forum/showpo...8&postcount=55

[lestr]

Re: Dell 1704FP LCD w/pwr but 2 secs to Dark

Can you take the resistance reading on all the pins of the OZ9930 with ref to ground (black probe on the chassis).

Readings are as follows. 1: 5.67M, 2: 5.68M, 3: 0 (GND), 4: 5.12M, 5: 5.12M, 6: readings are unstable; starts at about 1.5M, goes down to about 2k, comes up to about 0.5M, then comes down again in a period of about 2-3 mins., 7: 0.94M, and 8: 0.78M.

[budm]

Re: Dell 1704FP LCD w/pwr but 2 secs to Dark

Thanks! I am trying to see which one is the correct reading.
https://www.badcaps.net/forum/showth...697#post280697

What voltage are you getting on those pins. We may be able to fix both monitors.

[lestr]

Re: Dell 1704FP LCD w/pwr but 2 secs to Dark

Hey smason. Isn't this the same board used in the Dell 1905FP and Dell 1704FPt where they used the wrong capacitor near the transformer? The manufacturer missed a decimal point and they used a 22uF 50v where it should have been a 2.2uF 50v and it took out the transformer?
https://www.badcaps.net/forum/showpo...8&postcount=55

The capacitance of C112 and C113 in the inverter section are rated respectively as stated in the quote. I also questioned the difference as I was checking the caps since I expected consistency if the circuits are to be symmetric. Do you recall where that information can be found to ascertain what the capacitance of each should be? Thanks for your inputs.

[Lumberjack777]

Re: Dell 1704FP LCD w/pwr but 2 secs to Dark

The capacitance of C112 and C113 in the inverter section are rated respectively as stated in the quote. I also questioned the difference as I was checking the caps since I expected consistency if the circuits are to be symmetric. Do you recall where that information can be found to ascertain what the capacitance of each should be? Thanks for your inputs.

So it does have a 2.2uF on one side and a 22uF on the other? Yes, I have repaired a few of these. The 22uF 50v needs to be replaced with a 2.2uF 50v. The boards where there was a 22uF was present tended to take out the inverter transformer.

[lestr]

Re: Dell 1704FP LCD w/pwr but 2 secs to Dark

So it does have a 2.2uF on one side and a 22uF on the other? Yes, I have repaired a few of these. The 22uF 50v needs to be replaced with a 2.2uF 50v. The boards where there was a 22uF was present tended to take out the inverter transformer.

Thank you.

[lestr]

Re: Dell 1704FP LCD w/pwr but 2 secs to Dark

Thanks! I am trying to see which one is the correct reading.
https://www.badcaps.net/forum/showth...697#post280697

What voltage are you getting on those pins. We may be able to fix both monitors.

Did the resistance readings reveal anything?
Looking at the main board, I located two voltage regulators. I302 outputs 3.36v and I318 1.815v which matches their rating and shows the main board has power. I am not able to get voltages under operating conditions because the monitor does not stay on long enough to get a reading. However, by powering without turning on the monitor, the voltages at pins 6: 5.27v, 7: 2.52v with the remainder at zero.
Looking at your picture bucket there are some showing a miliamp meter being used to measure ESR with resistance measurements penciled in on the face of the meter. How did you figure what the ESR is with that setup? I used an AnaTek meter to test the caps in the power board and got zero for ESR on all of them. The capacitance with digital meter was ok. The caps are Capxons though. Any recommendations on this?

[budm]

Re: Dell 1704FP LCD w/pwr but 2 secs to Dark

I am still trying to figure out since I am also helping another person with the same IC.
I use 1% resistor also the reading from my SENCORE 75 to verify my meter.
To be accurate you should remove the cap from the board since a lot of time there will be lots of caps in parallel.

[KRS]

Re: Dell 1704FP LCD w/pwr but 2 secs to Dark

I am still trying to figure out since I am also helping another person with the same IC.
I use 1% resistor also the reading from my SENCORE 75 to verify my meter.
To be accurate you should remove the cap from the board since a lot of time there will be lots of caps in parallel.

Hello,

i have a problem with the power board 6832151100p03 ptb 1511 of the Dell monitor 1907FPVt.
For a projekt must die power board and the grafik board 15m away from the display.
The Problem ist now, the request of the backlight is coming to late.
Has someone a idea how can i bypassed it?
Or has someone the circuit diagram of this board?

Thank you for your help.

[boyebaran]

Re: Dell 1704FP LCD w/pwr but 2 secs to Dark

I'm a noobie who has been successful in fixing a few LCD's with standard through-hole components, but this 1704FP LCD has quite a few SMD's, something I had not tinkered with before. It all started with a no power indication. Opened up the case and found power supply components to be ok, resoldered in places that looked marginal, and replaced the shorted four FET's in the top-side of the inverter section. Powering up the board by itself, I got the following voltages at the output diodes (mounted on heat sinks): 5.3v, 12.7v, and 20.0v. At the connector P802 with the wires that connects the main board: pins 1-3, 5.3v; 4-7, 0v (grd), 8-10, 0v. With such encouraging results, I reconnected everything and repowered to get the power led to light up and for a few seconds show the OSB on the screen. By examining of the underside of the board where the SMD's are found, resistors are easy to identify but condensers are not marked. I was also able to read the markings on the following three SMD components which I don't have details for:

On the inverter side of the board,
I801: SG6841SZ, KMA233305490g
On the power supply side,
I101: OZ9930g, S1090122T, 0S46A
Q804: 13N06L

Markings on the Power-Inverter board: 6832151100-02, PTB-1511, 8/19/05.

Without a schematic and very little information on this model, it's hard to make much progress. The problem still seems to be in the inverter. Another burning question: are SMD components fairly easy to get and remove/install? Your insights and help to resolve this problem will be
much appreciated. Thank you.

hi
you can disable protection and see which part have a problem.most problems is in back light ccfls and high voltage transformer or mosfet driver (near high voltage trans).if u find damge mosfet check backlight and high voltage trans before replace mosfet

[boyebaran]

Re: Dell 1704FP LCD w/pwr but 2 secs to Dark

what means protection?
when some parts have a problem the led ccfls controller ic gone to protection mode for
Prevention more damage in inverter board.

[KRS]

Re: Dell 1704FP LCD w/pwr but 2 secs to Dark

what means protection?
when some parts have a problem the led ccfls controller ic gone to protection mode for
Prevention more damage in inverter board.

Thank you for your answare.
My problem is now how can i disable the protection mode.
When i run the board with the normal cable (20cm) then is everything fine (display works). But with the 15m cable the board goes after 2 sec. in the protection mode.

[boyebaran]

Re: Dell 1704FP LCD w/pwr but 2 secs to Dark

Thank you for your answare.
My problem is now how can i disable the protection mode.
When i run the board with the normal cable (20cm) then is everything fine (display works). But with the 15m cable the board goes after 2 sec. in the protection mode.

sorry .what means about cable (20cm)?

[KRS]

Re: Dell 1704FP LCD w/pwr but 2 secs to Dark

The distance between power board and display is normaly ~20 centimeter. I want to stretch the distance up to 15 meters. If i do this, the request of the backlight is coming to late and the board goes into the protection mode.

How can I disable the protection mode?