measuring again the components around the IC i found that R104 was blown...it wasn't obvious until i
looked at it from the sides and i've noticed the coating from the bottom side of the resistor was missing,
from the schematic i can see it goes to the pin that says ISENSE i guess it senses current...but since i
don't know much about switching power supplies i don't know if that resistor is the cause that the
previous IC got blown and now the new one is not functioning.
it's value must be 0.47ohm (yellow, blue or purple? and silver) and now it measures 7Mohm and it is 0.5W
which i don't have because it is rare number...with what else i could substitute that resistor?
do you think i should power up the supply after i change the resistor or it might blow the IC again?
thank you guys.![]()
Hi again,
Well, the current sense resistor could have blown because of an overcurrent, but i would think it would blow OPEN not to a near SHORT (or zero). This makes it hard to say if the IC will blow again or not, but usually the way power supplies are tested is the input is raised little by little checking everything with a scope and if anything looks wrong it is fixed before continuing. Once we get up to the full input voltage with no problems then we assume it's ok. This includes checking for spikes across the main transistor(s).
But as i said before, this is a difficult thing to fix without having it right in front of me where i can examine many aspects of it, and even then it may be too hard to fix. Could there even be something wrong with the thing it is powering.
That's another reason why i strongly suggest building your own power supply. Yes you have negative voltages, so what, that's what a power supply does
It's still up to you of course, but you may never get this fixed unless you get lucky.