HP w1907 Powers On Then Doesn't Detect Signal.

[zylcho]

Powers up fine, shows bios and refreshes to desktop for about 10 seconds then flashes "Input signal not detected" and shuts off. This happens in both VGA and DVI.

On dissection I see nothing visually that would be a possible suspect. Some minor oxidation of a few joints.

Video board "appears" to ok.

Any assistance in this would be greatly appreciated. Thank you in advance.

[delaware74b]

Re: HP w1907 Powers On Then Doesn't Detect Signal.

What brand and series caps on the power supply board? That board has lead-free solder and usually doesn't look good when compared to the old 60/40 lead/tin solder. I'd reheat those connections that don't look good and apply some 60/40 solder (if you're in the US).

[zylcho]

Re: HP w1907 Powers On Then Doesn't Detect Signal.

Couple different brand of caps, suscon, samxon, teapo and a symbol that looks like Leton. Sorry not quite following you as far as series?

Can you mix the 2 solders? Or do I have to remove all existing? As I have plenty of 60/40.

Yes I am in the US. Thank you for the assist.

[retiredcaps]

Re: HP w1907 Powers On Then Doesn't Detect Signal.

One cap series might say HM(M). It is a two or three letter code.

The 0405 (4 digit number) indicates year (2004) and the week (5th week) of when the cap was made.

I think that is Lelon.

Re the 10 seconds, try turning down the brightness and contrast down to say 25/100 and see if you get more than 10 seconds of operation.

Couple different brand of caps, suscon, samxon, teapo and a symbol that looks like Leton. Sorry not quite following you as far as series?

Can you mix the 2 solders? Or do I have to remove all existing? As I have plenty of 60/40.

Yes I am in the US. Thank you for the assist.

[zylcho]

Re: HP w1907 Powers On Then Doesn't Detect Signal.

OK powered on with Marlboro and plastic insulators to run while dissembled. The damn thing started working!

Of course passed all brightness tests as it is now working.

Been over 10 hours without power save and still good to go....

Did I wiggle something to cause this to function?

[zylcho]

Re: HP w1907 Powers On Then Doesn't Detect Signal.

Crap! Reassembled and back to original problem.... What I did notice now is that the blue power indicator (led) is now turning yellow (power save mode?)when the screen is not on.

So is not displaying "Signal not detected" anymore.

Screen turning off after 5 seconds and instantly turning power light yellow.

Could this be a problem with the video board?

[retiredcaps]

Re: HP w1907 Powers On Then Doesn't Detect Signal.

Try the configuration where you had it working for 10 hours again and see if it works. If it works, maybe check the cable connectors?

Also try gently rocking the caps back and forth to see if you have a loose solder joint. I found one cap on a Benq PCB board that looked good from the backside, but it was obviously loose when I rocked it back and forth on the frontside.

Crap! Reassembled and back to original problem.... ?

[zylcho]

Re: HP w1907 Powers On Then Doesn't Detect Signal.

Well it was dissembled when it worked for 10 hours, took apart again and same crap, no work.

I have stuck, measured, wiggled and inspected every "movable" part on both boards.
Will try some heat on the joints and see what that gets. Thanks for the reply.

[delaware74b]

Re: HP w1907 Powers On Then Doesn't Detect Signal.

zylcho, I try to remove as much of the lead-free solder as possible, but sometimes I have to add some 60/40 to the existing solder connection before I can remove the old solder or component. I'm willing to bet you have a cracked solder connectionon that board. It also sounds like the backlight circuit could be shutting down due to overload condition in either the inverter or you have a backlight starting to fail.

[mathog]

Re: HP w1907 Powers On Then Doesn't Detect Signal.

Powers up fine, shows bios and refreshes to desktop for about 10 seconds then flashes "Input signal not detected" and shuts off. This happens in both VGA and DVI.

I had a display where the VGA socket was slightly dirty inside. The DVI might have been too, don't know, didn't have a DVI cable to plug into it. Scraped out the inside of each VGA socket "tube" with a paper clip, which happened to be just the right size, and then a VGA cable was able to make a decent connection to the socket, and it saw signal. The display was still broken though in other ways. Apparently, the remaining failure had put it out of action originally, and then it sat around a long time with nothing plugged into the VGA port, so by the time I saw it VGA cables were not making an adequate electrical contact with the socket.

If you see the no signal symptom and there was no cable plugged into it when you first obtained the monitor suspect dirt in the video socket.

[zylcho]

Re: HP w1907 Powers On Then Doesn't Detect Signal.

Definitely not a dirty VGA socket. But thanks for the tip.

I took an iron to some of those oxidized joints and now monitor wont even attempt to power on. Not giving up just gets frustrating.

Thanks everyone for the assist. Will fiddle with later on.

[alexanna]

Re: HP w1907 Powers On Then Doesn't Detect Signal.

I have a very similar problem with several monitors. [ 2 sec off] I can not rembember the exact status of the power led, but running them on bench lcd out of case laying flat I could not get them to fail by wiggiling wires taping on screen they worked perfect. I have not run them for 10 hours, if they worked I put them back together,Then they would start their 2sec out problem. What I have found is poor or over heated wiring on the return side of the UPPER ccfls. Not sure why they work out of case laying flat other than added heat when they are assembled, an that heat rises.