Fixing Dell 2400MP projector with power supply PA-4331-1D-LF

Power, temp and lamp control lights are continuously on when projector is turned supplied. Nothing changes after pressing power button. In the user manual there is no description of such a combination of control lights.

Opening the projector:

There are silk screen descriptions on the PCB so it was easy to identify and measure voltages generated by the power supply PCB, the 5V net looked like this:

Which is mean that the power supply is not able to regulate voltage. It looks like a single cycle of the flyback is causing overvoltage and it leads to power supply shutdown and another try in couple of milliseconds when voltage drops to 4V. Visual inspection of the C206 5V output filtering capacitor reveals that the capacitor is swollen.

This capacitor has been replaced with a new low ESR capacitor but the power supply didn't start either. This particular power supply turns out to be very sensitive to correct filtering capacitors selection. After replacing the old capacitor with 3 electrolytic hybrid ultra low ESR capacitors the projector started working normally:

The C602 capacitor value is not critical (as long as it is at least 3300uF) but low ESR is.

I suppose that high temperature in the projector accelerated electrolytic capacitor's wear-out. Most of devices I repair is supplied by a flyback power supply and most of flyback power supplies suffer from issues with output filtering capacitor which usually works in high temperature, high current and high frequency.

Seeing problems with electrolytic capacitors another time I decided to buy a meter UT612 RLC meter:

I like price-quality ratio of UNI-T devices but looking at specs reveals, that the higher frequency you use for a measurement the lower capacitor values can be tested. In case of the projector with a capacitor of 3300uF I was able to measure ESR with highest  frequency of 120Hz. For a flyback power supply working with tens of kHz this measurement should be performed with at least 10kHz to reflect real conditions capacitor has to deal with.