Monitor Turns off without pressing the power button

This positively is a capacitor issue, when the caps are cold, they lose capacitance, if you put a blow dryer at the vents and warm the set up I'm guessing it will power on first time. I'd replace all the caps in the power supply section not just the ones that look or test bad

Have you checked your power supply voltages?...if so what are they?

Did you tried changing the lcd settings to default?

eMachines flat-screen monitors offer high quality at low cost.
eMachines flat-screen monitors are compatible with most brands of PCs.
Issues with eMachines flat-screen monitors can arise from faulty power sources, cable problems and incompatible settings.
These issues can be resolved by testing step-by-step each possible cause.

Plug the computer's power cable firmly into a working AC outlet.
Press the computer's power button.
Check the LEDs on the front of the computer case to confirm that the computer receives power.
Plug the eMachines monitor's power cable into a working AC outlet.
Press the monitor's power button.
Check the LEDs on the front bezel or power button of the eMachines monitor to confirm that the monitor receives power.
Orange or blinking LEDs indicate low power or no signal.
Green LEDs denote a working connection..

Perform a monitor self-test.
Switch off the monitor.
Unplug the video cable from the monitor.
Press the eMachines monitor's power button.
An eMachines logo, Windows logo or "no signal" message indicates that the monitor is working properly.

Plug the eMachines monitor's video cable into the video port on the computer.
Attach the monitor's included DVI-to-VGA adapter to the monitor's VGA cable if your computer has a DVI port (15 or 25 pin-slots with 1 side slot) in place of a VGA port (15 pin-slots, no side slot).

Press the eMachines monitor's input button to change the monitor's setting to match the computer port used.
Set your monitor to DVI if connected to your computer's DVI port.
Set your monitor to VGA if connected to your computer's VGA port.

Connect the eMachines monitor to a known working computer with a known working video cable if the problem persists. Contact Gateway, eMachines manufacturer, if the monitor issue is not resolved.

If its a flat screen monitor ?

eMachines flat-screen monitors offer high quality at low cost. eMachines flat-screen monitors are compatible with most brands of PCs. Issues with eMachines flat-screen monitors can arise from faulty power sources, cable problems and incompatible settings. These issues can be resolved by testing step-by-step each possible cause.

Plug the computer's power cable firmly into a working AC outlet. Press the computer's power button.

Check the LEDs on the front of the computer case to confirm that the computer receives power. Plug the eMachines monitor's power cable into a working AC outlet. Press the monitor's power button. Check the LEDs on the front bezel or power button of the eMachines monitor to confirm that the monitor receives power. Orange or blinking LEDs indicate low power or no signal. Green LEDs denote a working connection.. Perform a monitor self-test. Switch off the monitor. Unplug the video cable from the monitor. Press the eMachines monitor's power button. An eMachines logo, Windows logo or "no signal" message indicates that the monitor is working properly. Plug the eMachines monitor's video cable into the video port on the computer. Attach the monitor's included DVI-to-VGA adapter to the monitor's VGA cable if your computer has a DVI port (15 or 25 pin-slots with 1 side slot) in place of a VGA port (15 pin-slots, no side slot). Press the eMachines monitor's input button to change the monitor's setting to match the computer port used. Set your monitor to DVI if connected to your computer's DVI port. Set your monitor to VGA if connected to your computer's VGA port. Connect the eMachines monitor to a known working computer with a known working video cable if the problem persists. Contact Gateway, eMachines manufacturer, if the monitor issue is not resolved. Hope this helps.

Attach a USB connector to the iPod and plug it into a USB connection on a computer for power, or into a stand alone USB charger plugged into a power strip for electrical power.

Pick up the iPod. Move the "Hold" switch at the top of the iPod to the "Locked" position so that an orange color appears by the switch. Return the switch to the "Unlocked" position.

Repeat this process.

Press and hold the "Home" button and the button at the top right corner together if using a fifth generation iPod, iPod Nano, iPod Mini or iPod with a click wheel.

Press and hold the "Menu" button and the "Play/Pause" button together if using an iPod Touch. Press and hold the "Menu" button and the "OK" button together if using an older iPod.

Continue holding the buttons together until the screen flashes and then displays the iPod name and the Apple logo.

Release the buttons.

Wait as the iPod resets itself and turns itself back on.

or

Plug the iPod USB cable into the bottom of your iPod.

Plug the other end of the iPod USB cable into a free USB port on your Mac or PC.

Open the iTunes application by using the dock icon on a Mac or the start menu on a PC.

Click on the name of your iPod under the "Devices" list in the main iTunes window.

Click on the "Sync" button to create a connection between the computer and the iPod.

Click on the eject symbol after the syncing process is complete, and then unplug your iPod from the computer.

The lock code has been reset; when you go to disable the iPod again, you will be prompted to choose a new four-digit code.

hope this helps

Believe it or not but theirs an order in witch you should connect up a compute,r but first make sure that there is only 1 VGA port ie (monitor socket) on the back of it. But if theirs 2 then try the other one.
Other than that try this:
Unplug EVERYTHING! even the power leads from the back of the monitor & pc.
1.Press the power button on pc & monitor to flash out any power left in them.
2.plug in & tighten the VGA cable to the pc then to the monitor if required.
3.plug in all other peripherals ie USB / MOUSE / KEYBOARD etc...
4.plug in the power supply to the monitor then the pc.
4.Switch on the power supply to the monitor first then the pc.
5.Switch on the monitor by it's power button then the pc right after it.

Connect your phone to the computer and open iTunes. Hold both the home key and the power button until the iPhone turns off. Continue to hold them both for 5 more seconds. Release the power button but continue to hold the home button for 10 - 15 more seconds. I tunes should detect the phone in DFU mode. Restore firmware from this mode.

Hi,
Yes laptops can work without battery.
If the laptop is hanging on Dell logo and entering into BIOS then normally it is HDD issue but you have already checked without HDD so might be it is RAM or Board issue.
You can check with PC 133.
Please check your Laptop with minimal boot once (by removing all external hardwares like modem,tv tuner or graphics if any) and if you are geting the display one of the devices is causing the issue whch could be diagnosed by connecting one by one.

have u tried to unplug the power cord and open up the case aand unplug the power supply from the motherboard and then pressing the power button then plug the powersupply back into the motherboard and pluging in the computer and see what happens please keep me posted so i can help you more if needed ok best regards mike