It works fine with HDMI but fails using the other connector, or it doesn't work with either?

I just testet that - it is the same under DVI/HDMI connection.

Maybe the CCFLs are acting up? I remember some cases where fluorescent drew too much power and tripped the PSU protections...

Do you have all the drivers/tools provided for your video card and for the
monitor from the makers?

The tools sometime let you adjust things like resolution, vertical/horizontal
offests, and sometimes some very tricky signal timing/requirements.

I've seen a couple video setups over the years that could be set to settings that
made them unstable and shut down - often after a few seconds.

Do you happen to have DVI<>VGA and/or VGA<>DVI adapters?

If so, might be worth trying to see of it works cross-connect between DVI
and VGA (both ways if possible) - there are no guarantee because usually the
monitor has to support such adaptation - and it may use different
circuitry with one type of signal that the other...

But it might help narrow down where it's incompatible.

Also, if there's a "master reset" for the monitor, try it!
(I've seen more than one piece of equipment get discarded by a company thinking
it had failed - when in fact, some employee had just made a "bad setting")

And (I assume you've already tried this) - try it on several computers!

Dave ::: https://dunfield.themindfactory.com ::: "Daves Old Computers"->Personal

So, yes. I went thru all kind of test software and drivers, and today I tried 4 PCs/Notebooks - its all the same. Thanks, DaveDDS - I for now think it is not "software or function" - The factory reset was done by reflashing the BIOS/firmware. For now, I maybe follow Zup with the inverter... Now I have to find out how to measure that.

What about peeking at these service / repair manuals?

Hey Ho Ho Ho!

Thanks, guys - I have that service manual, and startet searching based on that.
Today finally I got a small step deeper into diagnostics. I think my problem is the backlight - and the "coil whining" i marked as acceptable maybe have to do with that (Both coils deliver 1,7MOhm when offline, so basically they are not shortetd, but why is one whing so bad in standby ...? )- or maybe the cap(s). I have all kind of caps, only 220uF are missing, so I order and replace the cap on the inverter first.

Update. No news. Changed the cap, no change. I think I give it up on that thing. If the inverter or the CCFLs are the problem it is not worth the effort... Well, damn. But, ok....

Have you tried if you can see the screen if you used a flashlight pointing at it at an angle? That way you can determine if it's really the backlight which is the culprit here.
If that's the case, there are LED upgrade kits available that you might want to try. Then you wouldn't need the inverter or the CCFLs anymore.

Wait, before you dump it.
Got a dead 17" Philps myself, that I want to rescue after Christmas holidays.
Dont have the exact model nr by hand but it may be similar to yours.
Depending where are you located we may swap spares to get at least one back to life.

Maybe reflowing soldrr joints?
I had that.

Long shot.

I had the exact same problem on my LG Flatron 17". It got to the point where I had to wait about 20 minutes for the light to go from standby to "on". This was many years ago now, but I recall replacing the caps on the logic board resolved the problem. Did you replace the caps on the logic board, or on the power supply board?

Any further with your monitor?
It is a 107B5 and the scaler/control board is looking the same, while the power board looks different.
Mine looks to have a problem with the CCFL converter, as the power supply seems to shut down frequently when poered on.