Another hp 1940 LCD problem- no picture-

[playman]

Hey there.
I've now fixed my other 5 HP's and the last one wants to give me some trouble.
I've changed the C5707 all 4 of them, and the FQU11P06 (located at Q812) wich was burned out.
The power on the screen stays on now, the power LED that is, but shows nothing.
I checked the BenQ board in a working monitor, and it was the same, no picture.
So I know it's the BenQ PCB board.

I've been trying to find how to check the FQU11P06 for foulty but no luck.
the FQU11P06 was from a spare monitor I had, so I plugged it in hoping that it worked.
Here is the Datashet for the FQU11P06


This is the thread that I started earlyer for the other HP1940, so the info and pictures should be the same,
otherwise let me know and i'll take a shot of the current PCB.
https://www.badcaps.net/forum/showthread.php?t=14068

P.S.
I took the chip out, becouse I did not get the same readings as if the chip was in, same as with the C5707's
I was not able to tell if they were broken or not if they were in the board.
Yea my Electronics skills and understanding is limited (ATM)

[alexanna]

Re: Another hp 1940 LCD problem- no picture-

Do you feel comfortable identifying the CCFL controller, and identifying that the correct voltages are getting to it? From your other thread it's the 16 pin IC on the bottom side in the inverter section.

[retiredcaps]

Re: Another hp 1940 LCD problem- no picture-

I checked the BenQ board in a working monitor, and it was the same, no picture.

Did you check the picofuse (PF801)?

[alexanna]

Re: Another hp 1940 LCD problem- no picture-

My eyes must really be getting bad I couldn't locate a fuse on the inverter.

[sabre504]

Re: Another hp 1940 LCD problem- no picture-

You can use a FU9024n to replace FQU11P06

[playman]

Re: Another hp 1940 LCD problem- no picture-

Do you feel comfortable identifying the CCFL controller, and identifying that the
correct voltages are getting to it? From your other thread it's the 16 pin IC on the bottom side in the inverter section.

I might be, if I knew what CCFL and IC would mean, 16 pin? you mean 11 Pin?

Did you check the picofuse (PF801)?

LOL damn you man, you got me there, ofcourse I did not check it, I don't understand why I
would not go for the "obvious" thing (altough becouse I noticed the light on the power LED I did not think of fuses)

My eyes must really be getting bad I couldn't locate a fuse on the inverter.

now now, you must have been tired, that's all ;-)

You can use a FU9024n to replace FQU11P06

thanks for that, i'll look into that if I find the FQU11P06 is broken.


But yes, the picofuse (PF801) was/is broken.
I tried to get some info about it, but could not get any match,
all I see is "bel MS 5A" on the fuse.
Any one have an idea where that datasheet is or suitable replacement part.
I also read somewhere that if the fuse blows, a another malfunction might be
the reason for the failure, any idea what that might be?

BTW how can I test the FQU11P06 (located at Q812)?

[Th3_uN1Qu3]

Re: Another hp 1940 LCD problem- no picture-

CCFL = Cold Cathode Fluorescent Light. Aka the lamps. Try another fuse - use a standard 5A fuse, i'm sure there's room to fit it. It may blow even if nothing else is wrong, if some of the panel cables have been shorted at a point in time. If you're lucky it'll work by just swapping the fuse.

[playman]

Re: Another hp 1940 LCD problem- no picture-

thanks for that uN1Qu3, but won't I need a certain Volt fuse like 12v 24v 230v etc.?

[Th3_uN1Qu3]

Re: Another hp 1940 LCD problem- no picture-

The voltage rating of a fuse is simply the voltage it can interrupt safely (without arcing).

Ohm's law says that current squared times resistance is power (I^2*R = P), in this context power = heat, heat melts the fuse. You can see that voltage does not participate in this equation. So, a fuse with a higher voltage rating can always be used, as long as it fits.

[playman]

Re: Another hp 1940 LCD problem- no picture-

Ohm's law says that current squared times resistance is power (I^2*R = P), in this context power = heat, heat melts the fuse. You can see that voltage does not participate in this equation. So, a fuse with a higher voltage rating can always be used, as long as it fits.

Ah sweet, then i'll plug in a 230v 5A fuse that I have here, since
I have no idea what voltage ran trough the fuse, i'll be using the 230v to be safe.
It's alittle larger but I think I can squese it in.

[retiredcaps]

Re: Another hp 1940 LCD problem- no picture-

I have no idea what voltage ran trough the fuse, i'll be using the 230v to be safe.

Most Benq style boards use a 3A 125v picofuse.

Before replacing the picofuse, you MUST resolder all 4 inverter transformer pins. If you don't, the picofuse will blow again (probably in less than 48 hours of use).

[playman]

Re: Another hp 1940 LCD problem- no picture-

Most Benq style boards use a 3A 125v picofuse.

and there we have it. Thank you retiredcaps.

Before replacing the picofuse, you MUST resolder all 4 inverter transformer pins. If you don't, the picofuse will blow again (probably in less than 48 hours of use).

I just replaced them all before I ran into the trouble that the screen would not show the picture.
But I can resolder them, just to be on the safe side. thanks again.

[Th3_uN1Qu3]

Re: Another hp 1940 LCD problem- no picture-

He meant the transformers not the transistors.

[retiredcaps]

Re: Another hp 1940 LCD problem- no picture-

He meant the transformers not the transistors.

Resolder all the 4 yellow square inverter transformer pins.

[playman]

Re: Another hp 1940 LCD problem- no picture-

He meant the transformers not the transistors.

Resolder all the 4 yellow square inverter transformer pins.

ah damn it lol thats what hapens when you dont pay attention to what you are learning. (coke? or beer? or maybee dark lager?)

[playman]

Re: Another hp 1940 LCD problem- no picture-

Good news every one!
I changed the fuse and it decided to work again :P

Thanks every one for your help and input.