This is my first thread on this forum, so I wold like to say Hi to everyone.
I'm from Poland, so please be tolerant in case of my spelling. I own LCD Portable AMD 286 from 1988. This computer was bought as new by my grandfather, and I would like to bring him to life. Below i put image how it looks like, on this image case is very dirty because I made photo just after i found him in the garage.

When I'm trying to turn this PC on, the power supply unit starts normally, fan in PSU working correctly, screen backlight is going bright, but nothing is displayed Diodes on the keyboard doesn't light up. System speaker is connected, but there is no sound (beep).
After turning this PC on, PSU is squeak quietly. So I decided to open the cover. Voltages on the PSU output are fine, I'm only not sure about plug that is conneted to the Graphic Card. Graphic Card has their 4-Pin plug, just like shown on below image...

I checked voltages on this plug, white wire is 230V AC , on the red wire - there is (as I remeber) about 9V DC. I'm afraid that 230V AC is not good value and it could destroy the graphic card or even more ... When this plug is disconected from graphic card, PSU starting to squeak louder, when I touch white and black wire for measurements with the multimeter, squeaking is quiet (similar like when it's connected to graphic card). I opened the PSU cover, inside I found below converter:

It looks, that this converter was added to PSU additionally. This converter has only 4 wires, two of them are supply (Ground and +5V DC), rest two are outputs (Ground and this strange 230V). When I disconnect yellow wire (5V DC) - PSU stops squeaking. I decided to replace electrolitic capacitors in this converter - without any results, there is still 230V AC on the white-black wires, and the squeaking is still audible (same level).

Below I attach graphic card image, I have two questions about this card:
1. What should be the voltage to supply this graphic card (on 4-pin plug)?
2. There is a switch on the graphic card "blade", it has two positions, I check both - without success. what is the function of this switch?

I have also one question about 2-Pin plug shown on below image:

This wires are going from PSU to the front of the PC. I did not disassemble PC to check where it is connected to ( I supose screen or power diode). Power diode on the front did not light up - so this is my favorite. Voltage between this wires is about 3V DC, but as you could see on the image, the wires are crossed. I did not try to change them. Is it ok, or i have to change it?

Thank you in advance for any help.