When the screen is black, shine a torch at an angle close to the screen and check for images.
They will be very faint if they are there, so trying this in a darkened room may help to see them.
''If there are images to be seen on the screen'', there's a backlight problem
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Here's the [https://www.manualslib.com/manual/558464/Samsung-305t-Syncmaster-30-Lcd-Monitor.html?page=7#manual|block diagram] from the service manual which may help although it's not a schematic.
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Here's the [link|https://www.manualslib.com/manual/558464/Samsung-305t-Syncmaster-30-Lcd-Monitor.html?page=7#manual|block diagram] from the service manual which may help although it's not a schematic.
Check if there is +24V on CN 402 (I don't know which pin so you may have to check all of them).
''If not'' then the problem is in the inverter section of the power board.
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''If there is'' check for voltage on the BL-EN(backlight enable) lead on CN 402. Again I don't know which pin and but maybe look for a voltage between 3V-5V as this is mostly the case with display backlight enable.
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''If there is'' check for voltage on the BL_EN(backlight enable) lead on CN 402. Again I don't know which pin and but maybe look for a voltage between 3V-5V as this is mostly the case with display backlight enable.
Usually there is always voltage supplied to the backlights but it is turned on and off in the screen by a signal voltage sent/removed on the BL_EN lead.
The way to find the lead maybe is to check the voltages on CN402 (all pins - write them down) when there is a display for the 10% of the time and then check again when there is no display.
''If there are no images'' then it's looking like a mainboard problem, especially if there is +24V for the backlights.
Hi,
When the screen is black, shine a torch at an angle close to the screen and check for images.
They will be very faint if they are there, so trying this in a darkened room may help to see them.
''If there are images to be seen on the screen'', there's a backlight problem
Here's the [https://www.manualslib.com/manual/558464/Samsung-305t-Syncmaster-30-Lcd-Monitor.html?page=7#manual|block diagram] from the service manual which may help although it's not a schematic.
Check if there is +24V on CN 402 (I don't know which pin so you may have to check all of them).
''If not'' then the problem is in the inverter section of the power board.
''If there is'' check for voltage on the BL-EN(backlight enable) lead on CN 402. Again I don't know which pin and but maybe look for a voltage between 3V-5V as this is mostly the case with display backlight enable.
Usually there is always voltage supplied to the backlights but it is turned on and off in the screen by a signal voltage sent/removed on the BL_EN lead.
The way to find the lead maybe is to check the voltages on CN402 (all pins - write them down) when there is a display for the 10% of the time and then check again when there is no display.
''If there are no images'' then it's looking like a mainboard problem, especially if there is +24V for the backlights.