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Hi Jestine ,

Can i check with you ,  if i measure the VCC pin of the power ic UC3842 and i get the reading not constantly example 11.xx dcv jump to 14.xx dcv then go down to 12.xx dcv and then up again , normally which parts did i need to check . Thanks

HI Chong,

It can be the IC itself have problem, the supply vcc line e-cap ESR value have shoot up or even if there is components shorted in the secondary side preventing the ic to start up. I suggest that you check all secondary output diodes first and filer caps, then optoisolator ic then back to the power ic.  Sometimes corresponding components to the power ic also could have problem

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HI Roland,

Good day Jestine,

Good day!

I would just like to inquire with regards to a burned varistor. I had a electronic control  board that has burned varistor and the part number was also

burned. Is there any way or technique that I can do to replace the burned varistor. i have measured the varistor and has a value of 27ohms which is i believe that is shorted and keeps on blowing the fuse.

Yes you are right by right it should not have any reading.

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