Fixing a flickering HP LCD monitor

[max347]

So I grabbed cheap HP 2509m off craigslist that exhibits a flashing screen (much like if your refresh rate is set incorrectly).

Everything displays perfectly, however it....flashes....as though the backlight is pulsing between medium brightness and high brightness. Sometimes when I turn it on, it actually corrects itself after a few seconds and works perfectly.

Now, I bought this with the intent to open it up and attempt to repair it. It is a sunk cost, and if I break it further I am not concerned. I bought it to tinker with. My question to the master tinkerers is- where do I start? My initial idea was to open it up and check all the caps. However, I saw in the menu that the monitor only has 3800 hours on it. I am not positive, but that does not seem to be too many?

Any ideas you can throw into the pot would be greatly appreciated!

Thanks

I am uploading a video right now, should be live in a few minutes-
http://youtu.be/0o58ZdAr42k

Pics of the internal boards-
http://imgur.com/a/u03sv

 

[PottedMeat]

checking the caps is a good start

i would open it up, pull out the backlight with everything still plugged in, turn it on and see if it really is the backlight and not the lcd/drivers itself.

 

[max347]

Thanks for the advise- though I am a little unclear as to how to differentiate between a problem caused by the LCD panel vs the backlight. Could I get some clarification on this?

As far as drivers, etc- The LCD flickers with just the menu with nothing plugged into it at all. My testing laptop displays perfectly on another monitor with the same settings (actually, 3 different ones). Additionally, I have tried all the different refresh rates...I am pretty sure it is a monitor specific problem. Maybe I missed something, but I have tried multiple inputs and settings.

If you could let me know on the backlight vs lcd that would be great. I haven't taken it apart yet, but I figured it would be one unit (so not easy to test).

I'll add some images to the first post of the power board and the input board. All the caps look fine to me unfortunately.

 

[PottedMeat]

Thanks for the advise- though I am a little unclear as to how to differentiate between a problem caused by the LCD panel vs the backlight. Could I get some clarification on this?

As far as drivers, etc- The LCD flickers with just the menu with nothing plugged into it at all. My testing laptop displays perfectly on another monitor with the same settings (actually, 3 different ones). Additionally, I have tried all the different refresh rates...I am pretty sure it is a monitor specific problem. Maybe I missed something, but I have tried multiple inputs and settings.

If you could let me know on the backlight vs lcd that would be great. I haven't taken it apart yet, but I figured it would be one unit (so not easy to test).

I'll add some images to the first post of the power board and the input board. All the caps look fine to me unfortunately.

sorry for the confusion - according to this site a similar model has a CCFL backlight http://reviews.cnet.com/lcd-monitors/hp-2709m/4505-3174_7-33743815.html

i mean that if you can pull out the backlight tube (even a little) and turn it on and the light is flickering - the problem is somewhere in the backlight circuit.

i would also check all the little ribbon cables and make sure they're secure

edit: i took a quick skim of your pics - didn't see any bad caps or board scorching, did notice this

is that some discoloration in the backlight cable? a burn?

 

[max347]

Ah ok, thats a great idea. For that, I will need to get to the panel and string out the connections carefully, so I will do that tonight and post findings late tonight/tomorrow morning.

Thats a good eye- but I think those are just marker marks from the original assemblers-

 

[max347]

Alright reporting back. It looks like there is a backlight on the top and the bottom of this model. Both backlights flicker.

I tried unplugging one backlight, and the screen then works fine with no flickering (albeit dimmer than normal, but perfectly viewable). However, after a few seconds the video cuts out (power button stays lit, but screen goes out (no image at all, not even a dim one as if the backlight was just shut off). I tried this with both backlights, same thing happened when either was working solo.

 

[kjband13oc]

I have one of these with same problem.Power supply to lcd is bad the components to replace on cheap power supply impossible to get.Could I get pic of bottom of board?

 

[max347]

Power supply to lcd is bad the components to replace on cheap power supply impossible to get.

Could you elaborate on this sentence? I am not sure exactly what you mean.

I'll grab a pic of the bottom tomorrow morning, but there are no burn marks.

 

[PottedMeat]

Alright reporting back. It looks like there is a backlight on the top and the bottom of this model. Both backlights flicker.

I tried unplugging one backlight, and the screen then works fine with no flickering (albeit dimmer than normal, but perfectly viewable). However, after a few seconds the video cuts out (power button stays lit, but screen goes out (no image at all, not even a dim one as if the backlight was just shut off). I tried this with both backlights, same thing happened when either was working solo.

seems like there's a backlight power supply problem, can handle one but not two, but it senses that there's one missing and shuts down. the only thing i can think of is to examine the undersides of the combo power board/backlight supply for cracked or bad solder joints. maybe disconnect/reconnect the control board.

I have one of these with same problem.Power supply to lcd is bad the components to replace on cheap power supply impossible to get.Could I get pic of bottom of board?

if this is true and it's one of the transformers you may be stuck getting a new power board

 

[max347]

Here is the back of the board-





Yeah unfortunately new boards are impossible to find, and repairs would cost $80

 

[kjband13oc]

That looks like the logic board I want to see the back of the power supply board.They sometimes have micro cracks in the solder that you can only see with a good magnifying glass.I sometimes can get parts from digikey,sometimes you can luck out and resolder the poorley soldered joints and get it working.

 

[max347]

That is the power supply board actually, note the power cord input in the top left of the first picture.

I looked around, but am finding no cracks. I'll borrow a good magnifying glass today and see what I can find with that. I'll post back tonight.

 

[max347]

Alright, well no cracks found. I am leaving for a week and will resume operation when I return. Thanks for all the ideas so far guys.

 

[603cmc]

Hey guys, hopefully posting in the right place. I have a 2 year old Lg 42ld550 LCD TV that is out o f warranty of course. I am now having problems where my screen is flickering with horizontal lines, the picture is being stretched and there is one big diagonal line periodically. This TV has been hanging on my wall and has never been dropped hit etc. I have the back open now and will post pics. Any help would be awesome! Thanks in advance.

 

[Rinaun]

I'd suggest taking full pictures of the PCB in order for us to diagnose this correctly. Pictures are worth 1000 words.

As someone mentioned earlier however, most of the flickering issues come from bad or failing capacitors. I would highly suggest checking each cap, or atleast providing us with a detailed non-blurred picture of the power supply section of the TV (usually has heatsinks, weighs a ton). When in doubt, take more pictures for us!

 

[gorobei]

As someone mentioned earlier however, most of the flickering issues come from bad or failing capacitors. I would highly suggest checking each cap, or atleast providing us with a detailed non-blurred picture of the power supply section of the TV (usually has heatsinks, weighs a ton). When in doubt, take more pictures for us!

most flickering issues with CCFL backlighting are from a failing inverter.

 

[Rinaun]

most flickering issues with CCFL backlighting are from a failing inverter.

I've fixed several CCFL monitors over the past couple months, and a few of them were fixed by replacing a blown capacitor; specifically samsung units. Samsung had issues with some very popular widescreen models from 2005-2009. I'm sure it could be an inverter, but without proper equipment the OP most likely won't be able to test the inverter. It would be much easier for him to upload pictures for us to visually confirm it's not a blown cap before we get any more detailed.

EDIT: I saw the OP posted pictures; bit sleepy, my bad! I did some more research on this particular model. I see it's mentioned several places that the CCFLs themselves become burnt on the ends. Here is what one user posted regarding this monitor:
"After I repaired two transistors on the Backlight Inverter module with similar parts - the original parts are very hard to come by (Niko Semi P5506BDG and P9006EDG Logic Level MOSFETs - for those who are curious), and their specific attributes are not easily found in what I could get my hands on. Anyway, after replacing these transistors I found there was a buzzing and dimly light lower left corner. I disassembled the monitor to find out that a wire to one of two lower CCFL tubes had totally burned open and was 'arcing' from the remaining stub of wire to the end of the florescent tube. (Relatively High Voltages are involved here, and can easily jump across a 1/8 inch burned up spacing.)"

If it is the inverter failing, it's going to make this repair much more difficult. One sidenote I found during research was that this monitor is notorious for having this issue. So far, I've read 3 different fix threads and not one of them turned out in a happy ending. The parts they used to make these monitors aren't easy to come by.

 

[jssp]

I had flickering monitor as well, turned out to be one wire to one of the back light bulbs had come loose and was arching, got lucky, I re soldered it and it now works.
Thanks everyone for the insights on monitor.

 

[mrbill08]

I just finished replacing the four backlight tubes for my HP2509m. The disassembly was easy and you don't need to take the entire LCD assembly apart because the backlight assemblies slide out. Just open the top metal frame enough to expose the ends of the backlights so you can slide them out.

After I slid out the bottom backlight assembly I had the same burned off white wire described in other posts - I cut off about 4 inches of that wire and replaced it. I could have just repaired that but as long as I had the display apart I went ahead and replaced all four bulbs with ones I had ordered from CCFL warehouse. The display is very bright and I had to turn the brightness down to 70 and may need to turn it down further as I am in daylight right now.
So before you suspect the inverter, check both backlight assemblies for this burnt wire issue, especially the lower one if you hear the sparking or arcing.

A couple of tips: order some rubber "figure 8" spacers - I'm glad that I did as I broke a few of the originals sliding them off the tubes. You may also want to order eight of those silcone rubber boots for the ends of the tubes. I did not and had to slice open the original ones. I re-sealed them with aquarium sealant.

This is not an easy undertaking and it took me several hours to finish including the curing time for the sealant. So if you are not "experienced" with soldering and electronic assembly, you might want to have CCFL warehouse rebuild the backlights for you.

Now that I am over the learning curve I can keep an eye out for more of these monitors being trashed or on the cheap.

Here is what I ordered:

Name Code Qty Each Options
-----------------------------------------------------------------------------
Standard Monitor Repair SMRK1 1 29.99 Manufacturer
Kit = HP
Model
# = 2509m
Screen
Size Diagonal = 25"
Screen
Size Horizontal = 21 3/4"
FIGURE 8's FIG8 8 0.25
Subtotal 31.99
Shipping 4.99
Tax 0.00
Total 36.98


Bill

 

[coolpurplefan]

I also bought an HP 2509m which says it was manufactured in July 2010. It can flicker with one computer then when I hook it up to another one, it can flicker for several minutes then stop. I kept it on that other computer for several hours working normally then switched it back to my main computer. After several minutes of flickering, it stopped and started working normally again.

Does that make any sense?

 

[SOFTengCOMPelec]

I also bought an HP 2509m which says it was manufactured in July 2010. It can flicker with one computer then when I hook it up to another one, it can flicker for several minutes then stop. I kept it on that other computer for several hours working normally then switched it back to my main computer. After several minutes of flickering, it stopped and started working normally again.

Does that make any sense?

When you turn on the monitor, it gets warm/hot inside. Electronic components, especially capacitors, change their characteristics, as they warm/heat up.
So if the flickering is because one or more components is on the way out and/or has changed/lost too much value (often capacitor(s)). It makes perfect sense for it to fail to work properly when cold, but as it warms up, it changes value (characteristics), enough to work again.
Eventually, you would probably find the flickering, lasts longer and longer (as the component(s) further deteriorate with age), until it flickers all the time or breaks altogether.

 

[coolpurplefan]

When you turn on the monitor, it gets warm/hot inside. Electronic components, especially capacitors, change their characteristics, as they warm/heat up.
So if the flickering is because one or more components is on the way out and/or has changed/lost too much value (often capacitor(s)). It makes perfect sense for it to fail to work properly when cold, but as it warms up, it changes value (characteristics), enough to work again.
Eventually, you would probably find the flickering, lasts longer and longer (as the component(s) further deteriorate with age), until it flickers all the time or breaks altogether.

OK, thanks I hope I can use it for another 2 months before buying another one.

 

[SOFTengCOMPelec]

OK, thanks I hope I can use it for another 2 months before buying another one.

There's a good chance 2 months will be fine.
By and large, components deteriorate fairly slowly (over years, or tens of years), unless something has gone badly wrong, such as a complete component failure or short circuit.

 

[coolpurplefan]

I just used some emergency money to buy an HP 25xi monitor because I saw it on sale at staples.ca (in store because it's out-of-stock online). It's an IPS and I just played the new Unreal Tournament pre-alpha demo (available if you register at https://forums.unrealtournament.com/forum.php ) and looked at some pictures and I'm fairly impressed. I can see different shades of colors for someone's hair on the HP 25xi (IPS monitor) compared to seeing like the same color with the HP 2509m (TN monitor). In Unreal Tournament, I can see lettering on the Enforcer (default gun) I didn't even notice on the TN monitor.

EDIT: lol, I just saw a video on Youtube comparing IPS to PLS. I found IPS looks washed-out compared to PLS having richer colors. They may say the viewing angles on PLS are narrower than IPS panels but before the 2016 Olympics, I may buy a PLS monitor. I want to keep the HP 25xi for now. I don't even want to return it because I like a 25 inch monitor and I like the fact it's a glossy panel.
As a side comment I can say I know everyone has a pair of eyeballs can can see colors. But my father was a painter for years. I can tell the colors on a PLS monitor look superior to me, especially the greens. I hope HP makes a 25 inch PLS monitor by next year. I don't think I can put two 27 inch monitors on my desk. lol

ANOTHER EDIT: I wonder if manufacturers could make stands that can be tilted forward just a little. My desk places the monitor at the height of my shoulders which means the slight back tilt seems odd to me. I wish it would tilt slightly forward.

AND ANOTHER EDIT: I could be incorrect about the IPS vs PLS because the HP 25xi is a glossy monitor so colors appear nice enough to me. The newer HP 25xw is now available at amazon.

 

[shiekh]

Normally it is swollen capacitors that need changing on the power supply, but I have seen this issue even after changing them; then treating the video ribbon cable with a little silicone oil seems to help.