HP W22 lights up then goes dark.

[weoxstan]

I have a HP W22 LCD monitor that when you first turn it on the screen lights up and you can see the test screen message. After about .5 - 1 sec it goes dim. You can still see the image but it is very dim. In the past I have been able to get it to work by turning it on and off but now it just stays dim after that first glimps. Looks like it is a backlite or inverter problem but looking for some guidence if anybody has had simular problems with this kind of failure? Any help would be appreciated.

Jeff

[Logistics]

Re: HP W22 lights up then goes dark.

I have a friend who just came to me with news that his HP W22 is also doing this. He says you see the picture for a moment, but then it shuts off. I haven't received it yet, but hopefully it will just be a cap problem. He had his broadband modem go out a little while back due to a power spike jacking up the caps; perhaps also weaking the caps in his HP display. I hope it's that simple because he gave me his previous 20" Trinitron monitor which was hardly used at all as payment for fixing his modem... it's only been a couple months since then and his beloved W22 dies like this. lol!

[Logistics]

Re: HP W22 lights up then goes dark.

Okay, so I finally got this thing apart. I've never taken apart a flat-panel monitor so it was scaring me, but I finally got all the ridiculous clips around the outer edge. GRRR!

Anyway, after examining the PSU PCB I don't see any bad caps. There are obviously a few caps that are smaller than the silk-screen allowed for; some 1500uF's where likey 2200uF's would have gone, but moving on the only visible sign of stress are a couple hot spots, one of which surrounds one of the sinked FETs or Voltage Regulators, whatever it is, numbered 9960GH on top and 623646 on the bottom, and then a couple of smaller guys on the backside of the PCB numbered 286 on top and SP10150 on the bottom. Other than that there is a tiny soic guy on the backside of the PCB which I'm not sure about. Everything is so covered in that sealant that goes over the PCB that it's hard to tell, but this particular little guy has a little bubble on one corner that has a white streak through it, but it isn't dry like other burned IC's I've seen, it's shiny.

Aside from all this all I can say is that just about every solder joint on the PSU PCB looks dry. They all have that nasty white dry look to them as if they weren't heated properly. There are relatively few joints that are smooth and shiny like a nice solder joint. I guess I could rewet everything just in case.

Any advice is appreciated as this piece is not obvious like other stuff I've fixed in the past.

[arneson]

Re: HP W22 lights up then goes dark.

Was this thing ever caught in the rain or stored outdoors.
That's the only time I've run into all solder joints as you described.

[Logistics]

Re: HP W22 lights up then goes dark.

I wondered the same thing, because I've seen hardware that got wet that looked like that, but it absolutely has not been in any water. The last piece of hardware this guy had was a DSL modem who's little wall-wart type PSU had it's caps go bad, presumably due to the power spikes of the rolling black-outs we had here during the previous summer. He had this monitor at the time so it's possible the spikes in energy also stressed this monitors components, but I can't see it affecting the solder joints. Thankfully, the way this monitor is designed, I can slap the PCB's back onto the backside and attach the stand without having to put the cover on so I can easily sit it on my desk and try it. I'll try re-wetting everything and see what happens since that's an easy to try fix that costs nothing.

[Logistics]

Re: HP W22 lights up then goes dark.

Okay guys, I'm about to pull the trigger on some new caps for this thing, but I can't find a suitable replacement for the big 150uF 450V jobber in the power stage... or at least not from Digikey, and I don't want to order from somewhere else. Does this thing really need to be 450V?

[Logistics]

Re: HP W22 lights up then goes dark.

Welp, I replaced all the caps with Panasonic FM's and FC's where necessary. The only thing I could not find a replacement for is the big 450V 150uF jobber. Anyway, it still has the same problem.

I can play with the buttons and it will go through this mode where it looks for a signal, and I see on the screen for a few moments, after it syncs up the SVGA port, that it doesn't have a signal on the DVI port (duh) and such, then it goes blank. I'm wondering if there's some auto-sensing component on the PCB that got fried in a power outage or something.

[davmax]

Re: HP W22 lights up then goes dark.

It would help greatly if you could supply a picture of both the top and botton sides of the power/inverter board

[davmax]

Re: HP W22 lights up then goes dark.

This check list may help.

Failed Monitor back light

Fault finding check list.
1. Check back light CCFL tubes to make sure that they are not broken.
2. Check all electrolytic capacitors for bulging tops and electrolyte stain (red/brown). Replace all caps with these problems evident.
3. Check the switching transistors that power the inverter transformers for a short circuit between the centre leg and the other legs. If there is a short circuit remove the pair of transistors.
4. If the transistors have failed short circuit check for a circuit fuse that may be blown or high resistance. Normal resistance is zero ohms. Additionally check for series regulating transistors that supply the failed switching transistor/s, there must be no short from the centre leg to the other legs. Replace if faulty.
5. Check the inverter winding resistances. The low voltage primary resistance should be less than 0.5 ohm. The high voltage output winding should measure between 500 and 1000 ohms. There are usually two transformers, compare the resistance readings, they should be approx. the same.
6. Make sure that all connections to the transformer are soldered well. To be certain heat each connection and reflow the solder using some new multicore solder.
7. There are usually several blue high voltage output capacitors that supply the CCFL tubes. These should be checked for a possible short circuit. Ideally they should be checked for capacitance value. These caps seldom fail hence they are last on the list.
8. Replace faulty inverter switching transistors once steps 4 to 7 are completed.

This above steps will cover the most common inverter failures. Powering up is the next step.

[Lawsonmh15]

Re: HP W22 lights up then goes dark.

I'm dealing with the exact same thing. Just wondering if anyone has tried to hook it up using a DVI cable? If so, did you get the same result?

Unfortunately, this is a notorious problem and from what I've read, HP will be of NO help and apparently the problem cannot be fixed. I'd love to hear if DVI works and that just the VGA port goes out as I got this thing for free and would love to use it if all it needs is a DVI cable.

[davg]

Re: HP W22 lights up then goes dark.

Hi I am new here but I am having this same problem I have checked the tubes and the caps and all seem to be ok. I am not sure however how to identify the the transistors so I have not checked them. Any help in this regard appreciated a picture or drawing would be great.

[PCBONEZ]

Re: HP W22 lights up then goes dark.

this particular little guy has a little bubble on one corner that has a white streak through it, but it isn't dry like other burned IC's I've seen, it's shiny.

I've has south bridges burned out by bad PSUs that had shiny spots.
Basically means it got hot enough to melt the casing.

.

[Logistics]

Re: HP W22 lights up then goes dark.

It would help greatly if you could supply a picture of both the top and botton sides of the power/inverter board

Is this it?

[PCBONEZ]

Re: HP W22 lights up then goes dark.


O
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C

[gonzo0815]

Re: HP W22 lights up then goes dark.

Most likely one of the CFL inverters transformer is bad, if cfl tubes and mosfet transistors are ok.
The over or under voltage or current at the high voltage output is monitored by the smps controller IC.
If it senses an failure it shuts down. I have seen this in some Medion 19 TFT`s. You can`t do much there, as you won`t get a suitable replacement transformer.
in th end the only way to fix it are those rather messy things like a complete cfl inverter or a completely new electronic innards.
At ebay you can get full electronic assembly for LVDS panels for about 50$ or four tubes cfl inverter for about 10 to 20$.

[Logistics]

Re: HP W22 lights up then goes dark.

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C

Nah, the IC with the white spot is on the opposing board with the audio stage and other stuff on it. I see why you thought I was confused, though.

[davg]

Re: HP W22 lights up then goes dark.

Just a update to this problem I have discovered that when I power up my unit the screen flickers quite a bit, come on I see my desktop than it goes black but if I disconnect p852 and power up there is no flickering my desktop displays quite clearly even long enough to bring up the menu than goes black?

[davg]

Re: HP W22 lights up then goes dark.

Another update and I hope I am not hijacking this tread but the backlights on p852 and p853 are not lighting so I just switched p852 and p853 with p854 and p855 and these backlights now light up. So the problem is in the circuit for p852 and p853. The backlights on that circuit are trying to lite up but for some reason can't (hence the flickering) Hoping one of the gurus can but a finger on this.

[weoxstan]

Re: HP W22 lights up then goes dark.

After reading the last post I decided to do the same test. I moved the pink and blue wires from the top P855 and P854 and pluged them in to the bottom P853 and P852 leaving the P855 and P854 empty and it lit up for a sec. Then I moved the pink and blue wires from the bottom P853 and P852 and pluged them in to the top P855 and P854 leaving the P853 and P852 empty and it did NOT lit up. Looks like the PCB is fine but the CFL Tube on the bottom is bad. Not what I wanted to find out...

[davg]

Re: HP W22 lights up then goes dark.

I know this is an old thread but I still have not resolved the problem with me unit. I just got back at it. when I plug the thing in I get a hissing sound at one of the backlight connections and it is actually burning with smell and smoke. If I disconnect that backlight the screen comes on and than goes off again but no burning. Is this a failed mosfet transistor? I am not sure how to test these transistors Do I have to take them out or can I determine this in circuit?