Usually if a CRT starts turning off on its own, simply dusting out the case solves the problem. But what you're describing sounds concerning. Try cleaning it out, but if that doesn't fix it, then it's probably dead.

loosing some colours and flickering sounds like a cable/connectors problem. Maybe worth checking them.

Either power supply or a short on the secondary side. Often the horizontal output transistor.

Flickering with a pulse sounds like PSU would like to start up but it can't. Check the power supply electrolytics for signs like bulging or leaking.

GPA wrote:

loosing some colours and flickering sounds like a cable/connectors problem. Maybe worth checking them.

the cable was ok, when happens that i had to beat the back of the monitor until the colors were ok again, 🤣, that was even worse at night because i have to keep the screen yellow or get ranted by my brothers.

h-a-l-9000 wrote:

Either power supply or a short on the secondary side. Often the horizontal output transistor.

i think that transistor is very susceptivble to heat, one thing i did not mentioned is days ago i had to move my computer to a VERY hot room with absolutely no ventilation at all, well , maybe that killed the trasistor? also, that flickering noise is very close to it, a very high pitch nose.

also i have a multimeter but no idea how to test them. replacing them couldnt be too hard.

Transistors won't squeal by themselves when broken.
Most likely there is something broken somewhere on the board, and that is just the primary (mains side) switching transistor of the power supply trying to power the thing.

Set the multimeter to diode test. Measure between C and E of the flyback transistor. If you get a 000 reading the transisitor or something nearby is shot.

You really need a Variac when testing these things after a repair, as in some cases the power supply is no longer properly regulating its voltage output to whatever it should be, example 110v DC,
it goes high and the horizontal output transistor blows, then if You simply replace it the same will happen again.
I used to repair these things for many years. Occasionally the Horiz transistor just blows for the hell of it, but rarely.
Realistically there are 3 possible problems

1. Power supply not regulating output voltage with possible horiz transistor also now shorted, could be caps in power supply.
2. Flyback is shorted
3. Horizontal output transistor is shorted

Hey! fellow Chilean, I have fixed a couple of those acer monitors, always the same failure in my case at least, Cold solder joints in some cases in the crt board, in the flyback and in the big transistors.

I had a 1080S monitor back in the day that acted very similar. It turned out the problem with that was some component/housing was building up a static charge. Wacking the monitor helped to discharge it. It was a very cheap repair but this was a long time ago and I don't remember the specifics.

PLEASE BE CAREFUL when doing anything inside a CRT device. The CRT gun is powered by 3K+ volts and there are capacitors that hold enough charge for quite some time. This a a very very dangerous voltage level.

yep, the death nipple is some serious shit, but ive done this before.

this week im gonna take a look to the solder joints then resolder them (crossing fingers). if that doesnt work i will take a look to transistors, a tecnician would be the last instance...