HP W19b Monitor Inverter/Power board ?'s Overheating?

[pyredex]

I have tested this monitor to find that after 20 minutes or so the inverter circuit shuts down. The display board is still functional (flashlight test). When the monitor is disassembled, it funntions longer. This tells me.. may be a big bad guess, but that something is getting too hot. I felt the 3 heat sinks on the board for about 30 minutes while the cathodes were on and found one gets significantly hotter than the other 2. I have pointed at this with a green arrow in the first image. The second is a closeup. These forums have been so helpful to me in the past just by reading and this is the first time I have posted. Thanks in advance for any help pointing me in the right direction.

[alexanna]

Re: HP W19b Monitor Inverter/Power board ?'s Overheating?

Are you noticing any flickering of the screen?

[pyredex]

Re: HP W19b Monitor Inverter/Power board ?'s Overheating?

None at all. Just goes black. Thanks!

[retiredcaps]

Re: HP W19b Monitor Inverter/Power board ?'s Overheating?

I have tested this monitor to find that after 20 minutes or so the inverter circuit shuts down..

What happens if you turn down the brightness and contrast to something like 50/30? Does it stay on longer?

[Rtech]

Re: HP W19b Monitor Inverter/Power board ?'s Overheating?

If I remember right, Alexanna had something the same as this,on another Monitor,and the problem was one of the backlights ??
I would try and eliminate them first by using test CCFLs and then running the thing and see if it runs for longer than 20mins.Also would think that the Heatsink mentioned would be hotter thn the other as it looks as though that is the Schottky that is feeding the Inverter/CCFLs.

[newbie1]

Re: HP W19b Monitor Inverter/Power board ?'s Overheating?

Agree with Rtech.

I am having a HP w1907 backlight shut-off after 20-30min. I substitute a spare CCFL on one of the bottom (IIRC) CCFL & it works more than 1 hour. However, i did not try to operate it with the cover off. BTW, i am still procrastinating on replacing/checking that CCFL or the wires. ..

[alexanna]

Re: HP W19b Monitor Inverter/Power board ?'s Overheating?

^
^
It might be a good idea to compare some resistances of the inverter transformers when there hot.
Also add fresh solder on the through hole components in the inverter area.

[pyredex]

Re: HP W19b Monitor Inverter/Power board ?'s Overheating?

I am having a HP w1907 backlight shut-off after 20-30min. I substitute a spare CCFL on one of the bottom (IIRC) CCFL & it works more than 1 hour. However, i did not try to operate it with the cover off. BTW, i am still procrastinating on replacing/checking that CCFL or the wires.

If I remember right, Alexanna had something the same as this,on another Monitor,and the problem was one of the backlights ??
I would try and eliminate them first by using test CCFLs and then running the thing and see if it runs for longer than 20mins.Also would think that the Heatsink mentioned would be hotter thn the other as it looks as though that is the Schottky that is feeding the Inverter/CCFLs.

I have 2 identical monitors that work properly, so I can subtitute parts. I will try to rule out ccfl's.

What happens if you turn down the brightness and contrast to something like 50/30? Does it stay on longer?

The monitor was at 50%, but I will try to raise/lower to see if it makes any difference.

It might be a good idea to compare some resistances of the inverter transformers when there hot.
Also add fresh solder on the through hole components in the inverter area.

I will resolder the joints and see if that helps too.

Thanks for all the great tips and also for helping me to understand that the one heatsink should be warmer! I will post results in a bit!

[jetadm123]

Re: HP W19b Monitor Inverter/Power board ?'s Overheating?

Since it looks like a heat related problem, may I suggest you take a hair/blow dryer and heat up various parts of the the board to see if you can accelerate the shutdown process. Hopefully, you'll be able narrow down the area that's causing the problem.

[pyredex]

Re: HP W19b Monitor Inverter/Power board ?'s Overheating?

I tested the transformers.. with a cheap meter, but found that they were consistant with eachother. Both primaries ohm'd at .439 and .438 Kohms. Secondaries across all pins were .2. I took the advice to resolder all thru board points. I ran the monitor at 100% brightness for over an hour and it stays on. I wonder if the problem is solved? The only way I can get it to fail (prior to hopeful repairs) was fully assembled and in the house. I'm in the garage now, and it is cooler out here. I will try this next.

Thanks for all the suggestions!

My next step I think will be the blowdryer if this didn't work.

[alexanna]

Re: HP W19b Monitor Inverter/Power board ?'s Overheating?

^
When I have had very intermittent 30 to 60 Min. to black problems caused by a CCFL, I have found that having the LCD lying flat will prolong the problem, where having the LCD in its normal upright position causes the problem to show up sooner.

[pyredex]

Re: HP W19b Monitor Inverter/Power board ?'s Overheating?

I ran it for about an hour inside wth no probs... Maybe a bad/weak solder joint? Alexanna, I'm just guessin those ccfl's aren't too easy to change out? I'd bet you could just buy a monitor on ebay that doesn't work and combine the 2. This is actually a 3rd monitor for me, I didnt want to buy 3 like monitors new and the only one like the 2 I had was broken on ebay...

Anyways. So far so good.. Thanks again everyone. This is a great place to find answers.