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G’day folks
My monitor is actually HP w2448hc, and the backlight is not working. The monitor seems to be producing the correct displayed signal, but can’t be seen unless in low light with a torch shining on the front of the screen.
How to access the backlight section, and check and repair it?
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Hi,
Don’t know the monitor but searching online seems to suggest that the backlighting is provided by a CCFL tube and not LEDs.
If this is the case it could be that the inverter power supply has failed or perhaps the tube itself.
Couldn’t find a schematic for the monitor which would help to check the inverter circuit, but if it is determined that the CCFL tube (aka lamp assembly) is the problem I found this guide that shows how to remove/replace it in a HP2509 monitor. I realize that it is not your model but it may be close enough to be of some help.
Here’s a link to a CCFL supplier that may also help.
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Thanks jayeff
I now have the actual disassembly manual for my monitor (cost me $5 from nodevice.com), and it looks like the CCFL is a series of six U shaped tubes up the whole screen. As none are on, I am hoping it might be the inverter, which would be way easier to access.
When time available, I will have a look inside and see if any telltale signs evident, and go from there.
I would be interested in anyone's experiences with troubleshooting this problem; i.e.; ascertaining if it is the inverter or the tubes, etc. It looks like there is a small shield over "the inverter" which may be accessible without taking too much apart. Just wondered if this means the lamp inverter, or a more general power supply for the whole system?
I have a digital multimeter, and electronics tech experience from 40 years ago.
Hi @ Frank ,
It could be that the inverter is part of the power supply or a separate board.
Check where the wires from the tubes go to.
If all of the tubes aren't working it does seem like the inverter is the problem as the monitor still seems to work of a fashion except for the backlights, so basically the power supply is OK.
Once you have found the inverter (or the power board if it is part of it) post some images of the board and also its board number. (printed on board itself) Here's how to do this on ifixit Ajout d'images à une question existante
It may be that if you can't see the problem and schematics aren't available the board number may help to find a replacement board.
I had this recently on an old 19" Benq monitor, where some of the switching power mosfets were open circuit in the inverter section of the power board. This was due to faulty transformers associated with them. The transformers were unobtainable due to not being made any more and with no suitable equivalents I opted to get a replacement board. The mosfets alone would have cost $US30 + shipping to Aust. whereas the replacement board only cost $US38 incl. shipping. Just something to consider if it gets down to this.
Cheers
@jayeff That's also why I don't fix the CCFL stuff anymore, outside of old high-end -- I'm not going on a wild goose chase for parts made of unobtanium when the odds the tube is nearing the end of its life is high now.
The line I drew on these reflects the quality of the backlight relative to the risk. On a high-end panel, the tubes are usually rated for ~10-20k hours and the entry level ones I left behind tend to be ~3-5k, or ~5-8k. With how old these are, the tubes are usually wearing out or worn. You usually have a shot at reviving the nice "pro grade" IPS/16:10 ones, but not the commodity ones.
The caps can also fry the tubes with voltage spiking issues, especially if they were used without addressing the cap issue! You could get a nice looking one with a tube that's not dead, but it's compromised due to the bad caps and then it dies in a few months.
That said, I realize not everyone needs a 2K 16:10 HP Z display, or even a 4K Z model and the entry level has it's place but the issue is when they break, they're hard to economically work with unless you get a unicorn failure.
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At this point, it’s usually the CCFL tube when it’s not LED, sadly. Now yes, sometimes it’s a bad inverter/power supply or bad capacitors, but that’s not the case like it used to be with many of these. Unless you get lucky and fix it with capacitors or a cheap inverter/power supply, it’s usually not worth repairing these monitors. It comes down to how hard it is to find the raw tube (most were recycled years ago, or they’re tired) and bare panels (again, usually they get recycled now and if you buy a used one, it may not have much left to give). SOMETIMES you can still find the tubes, but it’s not easy today due to the bulk of them being recycled due to the mercury.
You can try the capacitors as it’s a known issue with these monitors being from that period, but if that doesn’t work it’s time to give up and get a new one. Check both the power supply and controller board. It’s usually the power supply, but you want to check both to be safe with these capacitor plague monitors.
Personally, I’m at a point I will not fix a “capacitor plague” CCFL monitor unless it’s special, because the odds of the tube being bad aren’t in your favor these days compared to what the odds were 10 years ago (8 years from when I did the AL2216W for iFixit). By special, I basically mean it’s a unicorn matte 16:10 IPS with 1920x1200+ panel. These unicorn displays are often runover from when LED wasn’t mainstream in the pro market due to the color temperature not being there at the time for the pro grade displays. When I say pro, think HP Z, Dell Ultrasharp (5:4/16:10 IPS with factory color calibration), high end SyncMasters (again, see the note about Dell), NEC and ASUS PROART. Don’t let my refusal to bother anymore stop you if you insist on trying but keep that reality in mind.
Now yes, when we talk about modern LED panels with things like IPS panels being a standard feature since the market finally decided to leave TN and 16:9 behind to die outside of retailers like Walmart, 2K/3K/4K/beyond 4K things are a lot different — while I may not fix a 16:9 monitor from the era of CCFL as those are all low-res, I will work with a 2560x1440 monitor as the issues with 16:9 is beginning to get resolved with high PPI panels. 16:10 is also coming back as well, especially with high end monitors like the LG UltraFine, PROART, NEC, high-end Dell Ultrasharp and HP Z displays.
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