Intermittent LCD

[parispat]

Hi,

I've got an A31P 15" UXGA.

I replaced the backlight today (what an education on how LCDs work) and managed to get it all back together again.

Present symptom: the screen works for 2 seconds, bright like it should be, then the backlight cycles off. I can see the screen image is there.

When I do Alt F7 and cycle thru the 3 choices, the screen comes on again for the 2 seconds and the backlight goes off.

Any thoughts?

pARISpAT

[rkawakami]

Welcome to thinkpads.com!

Several questions:

- What was the source of the replacement backlight? Purchased new or extracted from another LCD?
- What was the previous problem with the backlight to cause you to replace it?
- What did you use as a guide on how to disassemble/re-assemble the panel? (I'm thinking about doing the same thing to a couple of my dead SXGA+ displays)
- Have you replaced the inverter board?

From the description, it sounds like maybe the inverter board is shutting down. Could be a few reasons why it would do so: mis-matched backlight, it's simply weak or worn out or something on the motherboard is causing it to turn off.

[SMA]

The CCF tube used to backlight the display is driven by a high AC voltage comming from the inverter.
It is in the 1000 voltage range so do not try to measure it without appropriate equipment and do not touch it with your fingers.
The voltage to start a CCF tube must be much higher then the operating voltage.
One example would be 1500 V ac to start and then 700 V ac to operate.
The startup voltage is generated by the inverter whenever the lcd has to be turned on - that is, at power on and at appropriate
points in the Fn+F7 sequence.

To me it seems obvious that the newly installed CCF tube's operating voltage requirement is higher than that generated by the inverter.

[The Spirit of X21]

Congratulations on replacing that backlight. I managed to do it once, but I found it quite difficult.