I've been using a 2005 production Samsung 204T in portrait mode since new. Lately it started failing to come on. It would flash briefly and go black until power cycled. After lots of tries it would eventually work with no issues of any kind. Only a problem if power cycled. Classic symptoms.
I took it apart and photographed it to send to @tom66 for advice. He kindly sent me the datasheet for the chip. While I had it apart I sprayed IPA on the PCB, scrubbed with an old toothbrush, blotted with paper towel and repeated. I then set up to monitor the chip at power on with my scope and a DIP clip. Critical level on the OVP pin is 2 V and I was seeing 220 mV. So far as I can tell it is "fixed" simply by cleaning the PCB and reseating the connectors! I could see almost no residue on the PCB, but did scrub away a few blotchy spots. The underside appears to have a conformal coating in addition to the plastic HV shield. The wash did make it look different, but not the way removing flux does.
If it's actually failing it should do it soon. If it's a "Clean me!" that's important. Non-smoker, so nothing but normal household aerosols. But not far from the dryer.
This would seem to have been dust that stuck to condensation in a humid climate over the course of almost 20 years. Blows my mind that would disturb the operation.
This makes an absurd amount of stuff I've "repaired" just by cleaning the PCB! It's crazy!!! Everything from consumer electronics to top tier T&M kit.
It's rather like reseating connectors. Electronics apparently also likes a bath from time to time in addition to a stroke or two ;-)
Have Fun!
Reg