laptop display flicker, inverter or backlight, or something else?

a client brought to me today one hp pavilion zv6000, 6 year old beast.

the problem is with the video to the attached display panel.  i will explain, and then after you read it, my question is:  is the problem most likely with the inverter, the backlight, or something else?  what part needs to be replaced?

externally attached monitor works perfectly.
tapping the rubber part that tells the laptop the display just closed, will make the display flicker for 0.25 seconds, enough to read one word.  during this 0.25 seconds, everything is tinted red, not sure if it's because it's not fully coming on, it's very quick.

i've unplugged and replugged the display lead that connects to the motherboard, no effect (it did flicker 0.25 seconds at that time though)

i've inspected the rubber part that tells the board that the display is closed or open, all seems to be in order there

probably not a bad video chip, since the external works perfectly
probably not a bad open/closed sensor, seems to work fine
not a loose cable (i've rolled it in my finger while on and it doesn't flicker)
the flicker only happens when power is re-applied to the display panel (either by switch or reconnecting the cable)
when "on", i can barely see the stuff on the screen if i use a flashlight
it flickers when i toggle the switch, so the backlight isn't 100% gone (can they partially fail?)

what's most likely broken?
are there any other troubleshooting steps i can go thru to nail it down?
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B HAsked:
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Sebastian TalmonConnect With a Mentor System Engineer Datacenter SolutionsCommented:

"when "on", i can barely see the stuff on the screen if i use a flashlight"

-> so it is not the video chip or video connection/cables etc., but something with the backlight

most likely it is the inverter, so I would recommend you start with replacing the inverter (it is relatively cheap)

A very good ressource for this problem is
Try the safe mode and see the display, is it fine or not?
B HAuthor Commented:
sorry, this happens at bios, completely independent of windows, drivers, normal or safe mode
it is purely hardware.
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nobusConnect With a Mentor Commented:
here a nice site to determine lcd problems, - AND they offer low cost repair :
If it is tinted red when it does come on then it is the LCD backlight. The best option is to replace the screen.
B HAuthor Commented:
@tacotec - that's a great link and is probably exactly right
@nobus - same for you too
@edbedb - while you're partially right, it being a probable bad backlight, replacing the screen won't fix it.  the screen, backlight, and inverter are all different parts.  you may have meant to replace the entire display assembly, but that's $150 as opposed to $15, and requires almost completely tearing the machine down, rather than just opening the display assembly itself.
@imadimad - you completely missed the point

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