Hp 1502

[matthmal]

Hi,

I have an HP 1502 Monitor which us not working fine. It has a white backlight and flickering screen. I opened it and found out 6 faulty caps: (C924, C925, C926, C929, C930, C932).

After reading this post: https://www.badcaps.net/forum/showthread.php?t=2658 i still can't sort the problem.

I also noticed a burnt area on the board near the ZD904.

Please find attached pictures of the boards for further help.

Hope that someone can help me.

Thanks,
Matthew

[Rtech]

Re: Hp 1502

Need a good,focused photo of the bottom of the Power Board

[selldoor]

Re: Hp 1502

Can you just confirm that you have three monitors (similar) that you are working on?

None of the pictures are clear enough for troubleshooting.

What make series of caps did you use

[matthmal]

Re: Hp 1502

Yes I confirm that I have three different monitors. Please find attached more pictures, hopefully clearer images. As for the other two monitors, I am going to upload photos on the other threads.

The Brand of the caps that I am using is: Yageo

[budm]

Re: Hp 1502

I would replace them all, as shown with red marking. They should be low ESR type.
You are saying the backlights are flickering?
http://s807.photobucket.com/albums/y.../HP/HP%201502/
It can be bad lamp assembly also.
http://s807.photobucket.com/albums/y...klight%20lamp/

[matthmal]

Re: Hp 1502

yes the backlights are flickering. The problem is that I can't find to buy one of the caps to be able to replace them all as one of them is 25V 150uF. Can this be replaced with a different one, if yes by which?

[budm]

Re: Hp 1502

You can use 220uF. Mian key is that, they have to be low ESR type.
Since you are working on three monitors, do you have one that uses the same lamp connectors to try it with this board to eliminate the possibility of bad lamps?
Since you are fixing many monitors, you may want to have spare lamps for testing, or make them:
http://s807.photobucket.com/albums/y...g%20old%20CFL/

[matthmal]

Re: Hp 1502

I am a beginner with boards, so after some googling I still can't understand what a low ESR is.

You mean I need to dismantle the screen to look for that? I'll try to do it although I doubt it that Dell and HP will be compatible with each other.

[budm]

Re: Hp 1502


http://en.wikipedia.org/wiki/Equival...ies_resistance

[matthmal]

Re: Hp 1502

all caps were changed and same problem persisted. still to test the bulb. will do that soon.

[matthmal]

Re: Hp 1502

can't find the place where the bulb is :S

[selldoor]

Re: Hp 1502

Hmm, try something else. In Pic 4 post4 at the top there are two sockets
with pink and white wires.
First try and change the plugs over - you may need to turn the board or the panel over to do this or have them stood on end. Move them into position without the power on then switch on as normal ( Sometimes one bulb/transformer is weaker and changing them over is just enough to stop flickering)

Next

Do either of the other two monitors have the same size plugs.
If so, you need to try and manoeuvre them so you can plug it in.
Again move without power til connected then switch on.

This is a double sort of test and may not work at all - it may come on
and flicker which suggests a different problem on the 1502
It may light up and stay on which suggests bad bulb or wiring on the
1502. AND proves that the lamps in the donor monitor are good.
OR it may not come on at all which suggests the bulbs or their wires in the donor monitor are bad

Hope this makes sense but just come back and ask if it doesnt. I know what I mean ( I think) but its not easy to convey

[matthmal]

Re: Hp 1502

The problem persisted when trying to turn the board in order to change the wiring.

I can't try the other display though as it has a different connection.

I did understand you I really appreciate your help

Does this mean that the monitor cannot be fixed?

[selldoor]

Re: Hp 1502

Does this mean that the monitor cannot be fixed?

No it does not mean that, it just means it is more difficult to test.
Are you able to build one of budm's test bulbs.

[matthmal]

Re: Hp 1502

I'll try to do it but I'm really not sure how am I going to connect a secondary wire to an existing socket.

[selldoor]

Re: Hp 1502

Ok Perhaps we can concentrate on this One as it works to some extent - flickers yes?

If you have a pc connected is there a picture?

Can you control the brightness/contrast if so can you lower them and see if it helps.
Also see if you can try different refresh rates to see if that helps.

Does the on screen display OSD menu come on

[matthmal]

Re: Hp 1502

Yes it does flicker.

I am connecting it to a laptop as a secondary display and shows the picture sometimes for 1 second and it flickers all the time.

I will try to control the contrast and so on but I have already tried to change the refresh rates and it remained the same.

No the OSD Menu does not come on when I turn on the monitor.

[selldoor]

Re: Hp 1502

Have you left it on for any length of time 30 minutes or so to see if the flahing stops. You say you can see the pic for one second - does it then go off.
What does the power led show?
Can you test the voltage at the dc cap on this one , meter on 600vdc
care High Voltage. Try to measure for 10 seconds - any variation.
Test the voltages between the power board and the main board.

[matthmal]

Re: Hp 1502

I have not left it on that long as i thought that i can do damage to the screen. Sometimes a picture shows for 1 second and the rest it flickers. Its like a bulb trying to turn on but never turns on. I will try that and post the results.

[selldoor]

Re: Hp 1502

Its like a bulb trying to turn on but never turns on.

That is more than likely exactly what it is - This is an old monitor and chance is that the bulbs are dying. This is the reason we were trying to get some sort of bulbs to try.- either from the other monitors or a DIY.
Do you have a broken laptop screen anywhere- the bulb from that might do.
otherwise its budms test bulb. If its not going to work anyway you have nothing to loose by cutting a lamp wire - the pink and white to get the plug.

If its discovered the bulbs are good after all then the wires can be resoldered and if well insulated should be ok.

You can also try to get further into the screen to get the actual panel out of the metal case in which case you/we might be able to see burnt bulbs or defective wiring - maybe just the insulation has has burnt and it is arcing to the frame.