Macintosh Classic not booting + screen not functionning

[jifke]

Hello, I brought out an old classic Macintosh. When I turn it on it is really doing something strange on the screen. I searched on the forums but could not find an equivalent topic. Has anyone ever had something similar? Where can this problem come from? Many thanks in advance !
View attachment IMG_6814.MOV

 

[Big Ben]

Hello
Did you replaced the motherboard and analog board capacitors?

Looks like the power supply can’t stabilize, which usually happens when the capacitor on the analog board goes wrong.

 

[ironborn65]

Open it and do a thorough visual inspection of the analog and the digital board.
When was the last time you turned it on successfully?
When I have a Mac which has been rested for years I inspect it inside before turning it on, you might damage it even more.