Electronics

From NuclearCat's homepage

Checking FET transistors

* For N-type 
** Touch black to D, then red to S. It should show around 500mV P-N voltage.
** Touch by red gate (G), then again S. Voltage will be much lower or zero, transistor is open.
** Keep red on S, touch by black now G. Now check black on D, red on S - it should be closed.

Failure on Daewoo LCD TV

Sometimes screen becoming very "green". Looks like unstable contact somewhere. After checking, found instability on LVDS connector on LCD controller board.

There is VCC, PLL and differential pairs. Differential pairs usually clearly visible on PCB - it is thick 0 line (ground?) and negative and positive from both sides of it. You can hook oscilloscope to P - you will see "positive" meander, then next 0 - zero, then "negative", opposite meander.

On my case failure was on first differential pair.

After checking by oscilloscope found difference between "green" and normal, one of differential pairs (negative?) was disappearing.

Checked on main board signal was disappearing too, what clearly shows shortcut of negative line to to 0 line. Cleaning of connector from possible remainings seems made TV to work stable.