Lcd monitor test

[Davi.p]

So it's time to repair this monitors with broken psus (bad main mosfet, rectifier shottcky diodes..) therefore i was watching for some repair techniques, i've read about the lamp in series and simultaneous use of a variac, since this tool is not on every hobbist house i wanna supply the transformer with what i have, ie 24v maximum (universal latptop psu or 2x12v lead batteries), i wonder if the psu can output a readable voltage, maybe without changing the feedback circuit it will go, under very low or null load, to maximum 4-5v where normally there are 12v and at 100% duty-cycle, but this ensures a right functioning? After to protect circuit i have to insert somewhere 2x 12v lamps in series to protect primary side.. i've read about starting the variac at 70v if i remeber but i don't have a 70v supply source.. thanks, bye.

[stj]

Re: Lcd monitor test

just use mains running through a halogen spotlamp.
if it's gonna blow, it's gonna blow - the lamp is just to reduce the chances.

a variac is going back to the old crt tv days - it can cause more damage than good on modern psu's because it can simulate a "brownout" condition with the supply looping between powerdown & start till it blows!

[Davi.p]

Re: Lcd monitor test

Hi, thanks, i've read about possible problems but not possible damages (to my memory), i don't understand well your last sentence, you want to say that the psu ic is designed to test the ac level so he expect in input at least a 110Vac rectified/filtered? So he needs an input to the Vin (startup voltage pin) as well as Vcc input and 24v are too low and ic shuts down? I have changed 4 main mosfets, them blows and the components spending as reached the monitor value... but i don't like to throw the sponge...