MONITOR REPAIR HELP Hi I would like to appreciate for your help I have got an Acer monitor model G781 CRT Type its switching power supply is not starting 300 volt supply is ok , Q602 (2SK1940 )& ic 601 (UC3842)have been changed with new one, voltage on pin 7 of ic601 is 12-15 volt(flactuating in between ) it should be 16 volt to generate Vref (5volt)on pin 8 of ic601 to start?!capacitor c626 have been replaced , but still does not start!& the fault is still unknowen ! Your help will be usefull.
Have you checked the horizontal output transistor for a short or leakage?? most of these sets will not start up unless the horizontal sweep sends the pulse to the power supply and says start me up!! I would look at bthe drive as well on the horiz. curcuit. If theres a pulsating voltage that means its waiting for something to signal it to work or its missing something.. Good luck
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HELP REQUIRED !
Checked output circuitry for short , there was no short .
As the primary & secondary circuit were checked for active components & suspecxted passive components,this time cheked the passive components very precisely & find out the R627 a 10K ohm resistor , in one end is 10k & the other end is infinity !
So replaced R627 , & the system is started .
After replacing IC101 ,Q102 , ZD602 , The finnal component to replace was R627 which is replaced & SMPS started .the finnal check was OK . GOOD LOCK
Checked output circuitry for short , there was no short .
As the primary & secondary circuit were checked for active components & suspecxted passive components,this time cheked the passive components very precisely & find out the R627 a 10K ohm resistor , in one end is 10k & the other end is infinity !
So replaced R627 , & the system is started .
After replacing IC101 ,Q102 , ZD602 , The finnal component to replace was R627 which is replaced & SMPS started .the finnal check was OK . GOOD LOCK
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