It turn on and i can get into the set up screen but when i turn it on it just goes to a black screen with a flashing line in the upper left of the screen

Black screen - no flashing white cursor in the upper left corner - no picture at all, i.e. the initial Dell start-up screen doesn't show up either:
- LCD is dead or isn't getting a signal - not an easy fix; or
- the LCD isn't being sent a signal - holding down the function [Fn] key and press display Function key to toggle through its settings (LCD panel only, Rear VGA output only, both LCD and VGA output)

Black screen - flashing white cursor in the upper left corner - the screen goes black after the windows loading screens come up but before the windows login screen comes up - it is probably a windows video driver problem. Try starting in Windows Safe Mode with VGA. Press [F8] after the Dell startup screen disappears to access the windows startup menu

Remove the HDD and test, replace if necessary.

The onboard video could have died. Plug in an external monitor and see if you get a display.

Try these steps

http://www.fixya.com/support/r3728860-troubleshoot_system_will_not_boot_hard

Thats the PIP (picture in picture), which lets you watch two pictures at once.  Push the PIP remote or go into the settings to turn the box off.

hi i have a 50" magnavox that has a problem, i was looking at several websites and i find out the dirfferent posibilities.
in your case i have 2 posibble answers.
1) negative image
tv turns on and shots down in 2sec
flashing pixels on screen
dark image
has sound but no video
screen goes black and then return to normal picture
vertical color lines on screen no video
vertical color lines with video
vertical bars on screen
horizontal lines on the image
picture goes red after while
IT COLUD BE (X or Y or Z SUSTAIN BOARDS )

2) just left part of screen working
just right part of the screen is working
vertical and horizontal lines on screen
part of screen not working
some functions not working
no video but has sound
functions not working at all
IT COULD BE (LOGIC CONTROL BOARD)
TErry HerreRA

RAM problem. Fix the RAM properly in the RAM slot.

PULL OUT THE MEMORY AND PUT THE OLD ONE BACK IN AND SEE IF YOU FIX THE PROBLEM.

Some 235s had a problem with the contrast setting. When the contrast is set to full the screen turns black.

When you turn on the GPS and the screen goes black, try tapping the left arrow on the track pad a few times. You should see the screen start to lighten. If that doesn't work, tap the power key and try tapping the left arrow a few times.

Beyond repair I would imagine - these thing cannot usuaslly be repaired in these circumstances.