I have got a hyundai monitor imagequest l50s , but the speakers won"t work

Plug the headphones/speakers into the computer. Go into Control Panel -> Sounds and Audio Devices -> Audio Tab -> Sound playback -> Select your headphones from the drop-down list. Voila headphones/speakers that work.

Since you install windows 7, you have to make sure you also install the correct sound card driver for it.

It is possible that the main board has some dry solderring joints. You will need to open the main board and check with a good lighting, a magnifying glass for finding the fault. Look for faulty connectors.Push them in and keep all connectors tight.
When the set cuts off check to see after disconnection of power if any of the components are heating up. If so check and see the reason ,may be drypoints must be checked on these components.
Check the voltage at the power on and off condition which can be a good indicator to the fault area.

Hope my advice helps.

that monitor doesnt have built in speakers

I have downloaded the manual from Hyundai website en_man_monitor_lseries_l52s.zip

a normal minijack (3,5 mm) cable, with the same plug in both ends.

if you have a cable already, try to adjust the volume using the buttons on the screen

the power button board is electronically fried you need a new one

Make sure the speaker input from the computer is plugged into the back.

Make sure the volume control is turned up and not muted on the front.

No it is not a backlight it is the inverter board which sends power to the backlight most likely cause is bad capacitors on the inverter board. this wil require soldering to repair backlight is even worse it requires you to disassemble the lcd unit. if you are gong to ope up the lcd monitor look on all pcb boards for deformed (blown) capacitors replace those with identical ones from yur electronics shop9they must be exactly the same mfd (Microfaradays) and Voltages

carefully remove the other covetr,isolate all wires connecting the electronic board to the crt and the earthing pad.once you acess the pcb,test the fuse first,if there is continuity,cover it back and seek proffesional service technician as further troubleshooting requires specialised knowledge.try your best,cos no one can fix every thing,most of the time we need other peolpe's services.i admire your courage. eyo7 [email protected]