Watara Supervision doesn't boot

[Alex4U]

yeah I can't believe I own one of these things, but the problem with this one is doesn't boot the bios screen I guess, I mean when I insert the cartridge, it doesn't show anything. Even the screen is always blank, nothing.
I already open and cleaned the motherboard. Still not luck.

So, uh, anything for restoring this?

 

[Alex4U]

I forgot to say the screen sometimes just goes black when I turn off. The motherboard is fine, but the cartridge slot has a cable to the motherboard (GND?) so I resoldered it, still not luck, I also checked the other badly ribbons on the motherboard, and they're fine, nothin' broken. the COM port is fine, Because I tested it with a Atari joystick (yeah you can put even a genesis controller, but it will has different effects) when I press the button, it resets automatically, the up down left right inputs doesn't seems to do anything, just the LED battery goes down when I press these buttons. The cartridge slot is fine also, everything working, but I didn't had luck booting this, the LED power turns on but nothing else, no sound, no inputs, no game, no contrast. So the screen is always blank, even on lower contrast is blank.

So, uh, maybe it's the motherboard?

 

[koffieleut]

Replace all the caps and look for board-rot.
It's like an old car, they need some love and new parts to work properly again