SMPS question

[W1RKW]

I have an LCD monitor that crapped out.  It turns out the switch mode power supply is at fault.  I put a resistive load on the SMPS and it would not supply power.  So I did a  litte trouble shooting and found that the power MOSFET in the SMPS was leaky.  I replaced it then put a resistive load on it (starting from 30 ohms to 4 ohms) and was able to get it to go without any trouble.  I was able to load test it up to it's rated output rating (4 amps at 14volts) for 20 minutes without any trouble yet when I connect it to the monitor it would not start up.  The monitor works OK but I can't get the SMPS to work with monitor even though the SMPS will put out power on a resistor.  Any ideas ?

[WD8BIL]

Check for an open or greatly changed pre-load resistor in the supply. 

[w3jn]

and check the ESR of the filter caps as well as the bypass caps on the PWM chip.  I just fixed a SMPS that would go into overcurrent shutdown because the bypass cap on the current sense input went into high ESR.

[W1RKW]

Turns out it was a  capacitor at the PWM that changed value slightly. Output voltage is stable and solid at any load including a no load condition. Thanks John.