HP LA1905WG lcd monitor no backlight

[shelby5041]

Re: HP LA1905WG lcd monitor no backlight

just took one apart down to backlight...it appears top left corner of plastic frame around backlight is melted/burned

[shelby5041]

Re: HP LA1905WG lcd monitor no backlight

will post a pic later...left corner of glass backlight metal frame burnt bad...actually its an end of a ccfl tube....fried........i just peeled it apart and its a tube thats on the uppermost part of frame.....

[shelby5041]

Re: HP LA1905WG lcd monitor no backlight

yep...just took another one apart.....left corner fried where ccfl wire around metal frame.....ccfl fried

[shelby5041]

Re: HP LA1905WG lcd monitor no backlight

ok this thread is done

here are pics of backlight assemblies for the 3 monitors that backight would power on for 2 seconds and then off

all 3 had electrical failures within the backlight circuit

seems to have to do with metal frame shorting out on power cable to ccfl

[shelby5041]

Re: HP LA1905WG lcd monitor no backlight

thanks to all that helped....i spent over 6 months on and off troubleshooting this issue....hundreds of hours..tearing apart power supplies...testing..desoldering...soldering......and was steered in the wrong directions due to my own mistakes.......but im glad to finally find the problem

[stj]

Re: HP LA1905WG lcd monitor no backlight

if you remove the melted tape & clean it up, you may just need to replace the wire section.

btw, this is not a surprise, the one i had (17 version) had a cracked tube!
HP overdrives the tubes in these monitors to get the brightness.

[shelby5041]

Re: HP LA1905WG lcd monitor no backlight

no.....the end of tube fried....broken./cracked..the reason its like this is these monitors are used in a manufacturing environment....lot of vibration and they are mounted on a fixture that moves back and forth 1200 times a day......thats what csused the problem.....broken monitors are ever day here.....we have about 500 in circulation.....and broken ones are a daily thing.....they throw them away and i sometimes take them....we now have all led style lcd monitors....they work great as lights when screens cracked

[budm]

Re: HP LA1905WG lcd monitor no backlight

That is why it is very important to have at least two good known test lamps to test the boards so you will save lots of troubleshooting times.

[shelby5041]

Re: HP LA1905WG lcd monitor no backlight

it was a good learning experience....

[stj]

Re: HP LA1905WG lcd monitor no backlight

you can still take the good tubes from one to fix another

[shelby5041]

Re: HP LA1905WG lcd monitor no backlight

not worth it.........

[shelby5041]

Re: HP LA1905WG lcd monitor no backlight

ill make more selling the boards....the monitors sell for only 20.00 used