Dear Experts,

I have a lovely IIYAMA LCD monitor which has developed a backlight fault.
Upon switching the monitor on the backlight is illuminated for a couple
of seconds and then extinguishes.
I have traced out the power supply and it's OK right to the cold cathode
inverter board. So I'm pretty satisfied it's not a PSU fault.
All the wires to this inverter assembly come from the main board and are
either +12V or grounded.
However there are just two of these wires (one yellow, one orange) that
seem to be active and go to the very large IC on the main board
(processor maybe?)
These both go high when the lamps extinguish.
The Cold cathode inverter board is an NEC HIU-391C.

Is one of these wires feedback to the processor telling it of a fault
and the other an output from the big IC to shut down the inverter board?

Does anyone have any schematic data for this board or anecdotal evidence
to aid repair.

One clue is that the illumination at the top of the screen appears to be
very dim (for the couple of seconds it's on).
Does this indicate one faulty inverter section or lamp?

I haven't tried to strip the lamp housing yet, I am still at the "learn
where all the screws go I've taken out already" stage.

Please help if you can
Thanks in anticipation....

Dave

Hey
Same problem with a different brand display. This converter is really
bad.
In fact, there is only on Oscillator and driver for 4 couples of
transformers (with on fuse for each couple). On IC (LM339 = 75339) is
in charge of HV current control. One of 4 values is out of specs,
oscillator is shuted down.
Work is in progress, but without schematic, it's a bit too hard.
And you, what about your progress??

On Mon, 07 Mar 2005 00:09:58 -0600, nath wrote:
Hey
Same problem with a different brand display. This converter is really
bad.
In fact, there is only on Oscillator and driver for 4 couples of
transformers (with on fuse for each couple). On IC (LM339 = 75339) is
in charge of HV current control. One of 4 values is out of specs,
oscillator is shuted down.
Work is in progress, but without schematic, it's a bit too hard.
And you, what about your progress??

Just _what_ are you nattering on about?