HP w1907 - 2 seconds to black

[jayoung]

I am attempting a repair of an HP w1907 for a friend of mine. It had 2 seconds to black symptoms. I took apart the monitor and used an old set of ccfl's to find that one of the ccfl's in the monitor was causing the issue. I ordered two replacement bulbs (one for the repair and one for possible breakage) from ccflwarehouse.com and received them in the mail today. I replaced the one that was causing the issue and the pair of ccfl's did not appear to be as bright as expected and then went off (2 seconds to black again). I thought maybe the two ccfl's were now drawing a different current (since one was old and one was new) and was causing the inverter to shut down again. I went ahead and replaced the second ccfl and still get the same symptoms. I can use my test ccfl's and things work fine, but with either or both of the new ccfl's plugged in I get 2 seconds to black. Is there now an issue with the new pair versus the old pair of ccfl's? Or is there something that I am missing? This is a 19" widescreen monitor with 2.4mm x 418mm ccfl's and my test ccfl's are from a standard 19" monitor if that information is helpful. Thanks in advance.

[alexanna]

Re: HP w1907 - 2 seconds to black

Voltage finding another way to ground,Look here

[jayoung]

Re: HP w1907 - 2 seconds to black

Voltage finding another way to ground,Look here

I actually thought about that myself. I checked the ccfl's even before I installed them in the panel. I also pulled the rubber boots back and separated the two ccfls by an inch or two - same result. Only part that could be an issue would be the plug end, but I can't believe that both of them are now having issues.

[jetadm123]

Re: HP w1907 - 2 seconds to black

I'm thinking that since your test set of ccfl's work fine, but not the new set, it might be possible that the new ccfl's require more current in order to operate correctly. It would seem the excess current draw is causing the over current protection circuit to trip. Try contacting ccflwarehouse to see what they think.

[alexanna]

Re: HP w1907 - 2 seconds to black

There are some small blue caps around the inverter transformers,do they look OK?
Good soldering and no burning?

[jayoung]

Re: HP w1907 - 2 seconds to black

I changed out the end plugs on both of the ccfl's with some extras that I had around. One of the metal connectors appeared to be bent slightly, possibly not making good contact, and I bent it back. It appears for the time being that this helps. I have to put the ccfl's back in the panel and I will update when I complete that task. Thanks alexanna.

[jayoung]

Re: HP w1907 - 2 seconds to black

The ccfl's are stilling shutting down the monitor when plugged in (one or both of them). Monitor still runs with the spare set of ccfl's that I have. I have also noticed a faint "sizzling" sound coming from the inverter (have not pinpointed the exact location), so I am going to check the solder joints hopefully tonight when I get home and see if reflowing any of them helps.

[jayoung]

Re: HP w1907 - 2 seconds to black

There are some small blue caps around the inverter transformers,do they look OK?
Good soldering and no burning?

All four of the small blue caps appear O.K.

I re-flowed both connections of each of the four blue caps, all eight of the pins to the transformer, and the four connections to each of the four plugs for the ccfl's.

I took some pictures of the power / inverter board and they are included.

The system works with two of the original ccfl's and two of my spare ccfl's. When I plug in the two new ccfl's, the system exhibits two seconds to black. Sometimes I can get the system to stay on with just one of the new ccfl's plugged in along with one of the spare ccfl's. I have tried the two new ccfl's in both sets of the plugs for the ccfl's.

I made the following resistance measurements on the transformer:
Best I can come up with for the number:
6131040001P20
DARFON 4308A 706094

DMM probes touching - 0.4 ohms

Between pins:
1 - 2 - OL
1 - 3 - OL
1 - 4 - OL
1 - 5 - OL
1 - 6 - OL
1 - 7 - OL
1 - 8 - OL
2 - 3 - 0.4 ohms
2 - 4 - OL
2 - 5 - OL
2 - 6 - 0.4 ohms
2 - 7 - 0.4 ohms
2 - 8 - OL
3 - 4 - OL
3 - 5 - OL
3 - 6 - 0.4 ohms
3 - 7 - 0.4 ohms
3 - 8 - OL
4 - 5 - OL
4 - 6 - OL
4 - 7 - OL
4 - 8 - OL
5 - 6 - OL
5 - 7 - OL
5 - 8 - OL
6 - 7 - 0.4 ohms
6 - 8 - OL
7 - 8 - OL

Do these measurements appear to show that transformer is not functioning properly? If so, does it make sense that it works with the spare ccfl's installed?

[alexanna]

Re: HP w1907 - 2 seconds to black

There is an Ohm reading missing,
the secondary's usually run somewhere between 500 and 1500 ohms, you may want to clean the pins and retest.The secondary pins are most likely the pins at the outside edge of the transformer,they should be paired on opposite sides of the transformer.
Are you still hearing the sizzling noise?

[retiredcaps]

Re: HP w1907 - 2 seconds to black

I'm guessing the secondary pins are the one at the 4 corners by looking at the bottom pcb picture.

[jayoung]

Re: HP w1907 - 2 seconds to black

There is an Ohm reading missing,
the secondary's usually run somewhere between 500 and 1500 ohms, you may want to clean the pins and retest.The secondary pins are most likely the pins at the outside edge of the transformer,they should be paired on opposite sides of the transformer.
Are you still hearing the sizzling noise?

Opps, I had the DMM setting on 200 ohms scale.

With the DMM setting to 2000 ohms:

pin 1 - 5 - 577 ohms
pin 4 - 8 - 575 ohms

I would say it's more of a buzzing sound. I took all the boards out of the monitor and connected everything on the table. It's still hard to determine exactly where it's coming from, but I would say it from transformer (?) next to the main plug and beside the fuse.

[retiredcaps]

Re: HP w1907 - 2 seconds to black

With the DMM setting to 2000 ohms:

pin 1 - 5 - 577 ohms
pin 4 - 8 - 575 ohms

The inverter transformers are within 3% of each other so they are likely good.

[jayoung]

Re: HP w1907 - 2 seconds to black

I'm thinking that since your test set of ccfl's work fine, but not the new set, it might be possible that the new ccfl's require more current in order to operate correctly. It would seem the excess current draw is causing the over current protection circuit to trip. Try contacting ccflwarehouse to see what they think.

Sorry jetadm123, I somehow missed your comment. I just sent an e-mail to ccflwarehouse.com to see what their thoughts are concerning this issue. It appears they have hours during the week and on the weekends, but not after 5:00 PM CST. Hopefully I will get a reply from them.

[alexanna]

Re: HP w1907 - 2 seconds to black

I am about out of gas tonight, but one suggestion before I put it to bed.
I have seen so many of these monitors with loose wring causing shut down, I am going to ask you to verify your wiring and soldering. Without breaking the new CCFLs give the wires a fairly sturdy tug, make sure it has a good connection.

[jayoung]

Re: HP w1907 - 2 seconds to black

I am about out of gas tonight, but one suggestion before I put it to bed.
I have seen so many of these monitors with loose wring causing shut down, I am going to ask you to verify your wiring and soldering. Without breaking the new CCFLs give the wires a fairly sturdy tug, make sure it has a good connection.

I have done that and actually went back, heated the joints, and added solder to the connections.

Thanks for the suggestions everyone, I really do appreciate it.

We'll see what ccflwarehouse.com may have to say.

[retiredcaps]

Re: HP w1907 - 2 seconds to black

Try this. Most monitors are set to 90 brightness and 70 contrast.

Hookup your working ccfls. Set brightness and contrast to 25 and 25. Power off properly so these settings are saved.

Now try new ccfls. Any change?

[alexanna]

Re: HP w1907 - 2 seconds to black

I wonder if you haven't done so if you would try something.
Number the inverter plugs 1 2 3 and 4
Install the 2 new CCFLs in plugs 1 and 2 with the older CCFLs in plugs 3 and 4, check the operation, and then install the new CCFLs into 3 and 4 with the old CCFLs in plugs 1 and 2. Dose anything change?

[jayoung]

Re: HP w1907 - 2 seconds to black

Try this. Most monitors are set to 90 brightness and 70 contrast.

Hookup your working ccfls. Set brightness and contrast to 25 and 25. Power off properly so these settings are saved.

Now try new ccfls. Any change?

I installed my two spare ccfls and lowered the brightness and contrast to 25 each. New ccfls still cause 2 seconds to black.

I wonder if you haven't done so if you would try something.
Number the inverter plugs 1 2 3 and 4
Install the 2 new CCFLs in plugs 1 and 2 with the older CCFLs in plugs 3 and 4, check the operation, and then install the new CCFLs into 3 and 4 with the old CCFLs in plugs 1 and 2. Dose anything change?

I had tried various combinations already, but here are the results.

Original ccfls in 1 and 2, replacement ccfl in 3 and 4 - 2 seconds to black
Original ccfls in 1 and 2, replacement ccfl in 3, spare ccfl in 4 - 2 seconds to black
Original ccfls in 1 and 2, spare ccfl in 3, replacement ccfl in 4 - 2 seconds to black
Replacement ccfls in 1 and 2, spare ccfls in 3 and 4 - 2 seconds to black
Replacement ccfl in 1, original ccfl in 2, spare ccfls in 3 and 4 - normal function
Original ccfl in 1, replacement ccfl in 2, spare ccfls in 3 and 4 - normal function

[jayoung]

Re: HP w1907 - 2 seconds to black

Here is hopefully the final update:

I never heard anything from ccflwarehouse.com concerning the e-mail that I sent to them inquiring about this issue.

I came home from work today and figured on trying the new ccfl's in a different 19" widescreen monitor to see if the problem followed the ccfl's. In setting up the disassembled monitor it was required that I hold the ccfl's by both hands so as not to short out anything. The ccfl's stayed on and I noticed that as I removed one of my hands to unplug the monitor that the bulbs would dim. I plugged the ccfl's back into the monitor that was having issues and the ccfl's would remain lit as long as I was holding them with two hands. As soon as I let one hand go, the monitor would shut off. I am assuming from my limited experience in lcd monitor repair that the ccfl's appeared to be vibrating and possibly causing a higher current pull which was causing the monitor to shut down. I'm not sure if this is the case or if this is something that most people experienced in lcd monitor repair would know.

I installed the ccfl's in the metal rail and re-assembled the lcd panel. The monitor appears to work as expected and has been on for about an hour and fifteen minutes with no issues.

I really do appreciate all of the help from badcaps.net in repairing this monitor and saving it from the electronics recyclers.

[retiredcaps]

Re: HP w1907 - 2 seconds to black

I never heard anything from ccflwarehouse.com concerning the e-mail that I sent to them inquiring about this issue.

I have no vested interested (financial or otherwise), but members experience good service from them if you pick up the phone and call them. Sometimes emails get lost?