Hello all, i've just signed up to this forum to ask a question about a psu that i just blew.
While assembling a new computer build i was unable to find my anit static wrist band so i made the mistake of rigging up a makeshift one because i was sick of having to go over to where i had a powersupply to touch it to discharge. This was done by clipping an aligator clip to the outside case of the psu and attaching the other end to my wrist with an elastic.. i had a look inside the grate where i clipped it to make sure there were no components the clip could acidently touch and seeing only a heatsink i thought this would be fine, there was enough clearence anyway. Having checked earlier that this psu was off, i foolishly didnt re-check this.
Anyway at some stage i moved a bit further than the alligator clip cord would allow and the tug on the cord caused the clips teeth to slip and it made contact with the heatsink. I heard a pop, and when i looked over there was a bit of smoke from where the arc had burnt a hole in the heatsink 1 or2mm deep. Very Fortunately for me the current would have run from the heatsink to the alligator clip then back to earth via the outside case of the psu, instead of up the wire into me! i perhaps owe my life to path of least resistance! this is certainly not a mistake i will be making again.
Upon inspection of inside of the psu i was unable to see anything abnormal at all (bar the burnt in dent on the heatsink!) that is, no buldgeing caps, no burnt coils or any other burn marks of any kind etc. having finally found the fuse (sneaky thing was wrapped up and hidden away) i managed to cut off the plastic wrap and seeing as it is ceramic tested it with a multimeter (continuity at least, multimeter on the fritz. it just counts upward when on Ohms) and found there is no continuity. this is while it is still attached mind you.
Having browsed this forum ive answered my first question which was "is it normal for the heatsink to be electrified" and i see now that primary heatsinks often are, something i will remember for the future. However, i was a little concerend with how little clearence there is between this heatsink and some parts of the case considering its design (3 sides removable cover, slots over but only has screws on the top. so the 2 sides have a bit of 'give' in them.)
anyway, my real question is, considering the events that i have described, is it likely that any other parts of this psu could have been damaged in a non visible way. or seeing that the current went really straight back into the case and to ground would this avoid damage to the psu (and also to the motherboard that it was plugged into... yes yes i know. incredibly foolish of me) from my above average-joe but still very much basic understanding of electronics my feeling is that the motherboard etc will be ok. however im not sure about the components that lie in betweent the fuse and the heatsink that shorted with the case. what other components are involved in the over current protection? im not sure if the IC that controls some of the other protections does that aswell. if the IC does the OC aswell, would it likely to be damaged? normally it would just switch off wouldnt it? or are the IC controlled protections only for the outputs and not intended for this kind of short. I presume these would have assisted in protecting the motherboard. it wasnt switched on just in standby. thats what i get for not re checking that things are off. I am currently looking up how to test some of the other components in the psu
so really im hoping that if i replace this fuse i will be able to salvage this psu. from what i have read most people seem to agree that replacing this fuse with a glass instead of ceramic will be ok, but i will try to get a ceramic. if memory serves it was either a T6.3A 250v or T8A. both were listed for different wattage psu, of course i will confirm this before switching it.
unfortunately its the type with the end caps and wires and soldered onto the board and it really is in quite an awkward location, so before undertaking this task and possibly just making things worse i thought i would ask for some opinions from you all here who know much better than i.
sorry for the long post, just trying to include as much detail as possible. any advice would be much appreciated. thankyou, James.
p.s if photos would help i can provide these as soon as i get a chance.
While assembling a new computer build i was unable to find my anit static wrist band so i made the mistake of rigging up a makeshift one because i was sick of having to go over to where i had a powersupply to touch it to discharge. This was done by clipping an aligator clip to the outside case of the psu and attaching the other end to my wrist with an elastic.. i had a look inside the grate where i clipped it to make sure there were no components the clip could acidently touch and seeing only a heatsink i thought this would be fine, there was enough clearence anyway. Having checked earlier that this psu was off, i foolishly didnt re-check this.
Anyway at some stage i moved a bit further than the alligator clip cord would allow and the tug on the cord caused the clips teeth to slip and it made contact with the heatsink. I heard a pop, and when i looked over there was a bit of smoke from where the arc had burnt a hole in the heatsink 1 or2mm deep. Very Fortunately for me the current would have run from the heatsink to the alligator clip then back to earth via the outside case of the psu, instead of up the wire into me! i perhaps owe my life to path of least resistance! this is certainly not a mistake i will be making again.
Upon inspection of inside of the psu i was unable to see anything abnormal at all (bar the burnt in dent on the heatsink!) that is, no buldgeing caps, no burnt coils or any other burn marks of any kind etc. having finally found the fuse (sneaky thing was wrapped up and hidden away) i managed to cut off the plastic wrap and seeing as it is ceramic tested it with a multimeter (continuity at least, multimeter on the fritz. it just counts upward when on Ohms) and found there is no continuity. this is while it is still attached mind you.
Having browsed this forum ive answered my first question which was "is it normal for the heatsink to be electrified" and i see now that primary heatsinks often are, something i will remember for the future. However, i was a little concerend with how little clearence there is between this heatsink and some parts of the case considering its design (3 sides removable cover, slots over but only has screws on the top. so the 2 sides have a bit of 'give' in them.)
anyway, my real question is, considering the events that i have described, is it likely that any other parts of this psu could have been damaged in a non visible way. or seeing that the current went really straight back into the case and to ground would this avoid damage to the psu (and also to the motherboard that it was plugged into... yes yes i know. incredibly foolish of me) from my above average-joe but still very much basic understanding of electronics my feeling is that the motherboard etc will be ok. however im not sure about the components that lie in betweent the fuse and the heatsink that shorted with the case. what other components are involved in the over current protection? im not sure if the IC that controls some of the other protections does that aswell. if the IC does the OC aswell, would it likely to be damaged? normally it would just switch off wouldnt it? or are the IC controlled protections only for the outputs and not intended for this kind of short. I presume these would have assisted in protecting the motherboard. it wasnt switched on just in standby. thats what i get for not re checking that things are off. I am currently looking up how to test some of the other components in the psu
so really im hoping that if i replace this fuse i will be able to salvage this psu. from what i have read most people seem to agree that replacing this fuse with a glass instead of ceramic will be ok, but i will try to get a ceramic. if memory serves it was either a T6.3A 250v or T8A. both were listed for different wattage psu, of course i will confirm this before switching it.
unfortunately its the type with the end caps and wires and soldered onto the board and it really is in quite an awkward location, so before undertaking this task and possibly just making things worse i thought i would ask for some opinions from you all here who know much better than i.
sorry for the long post, just trying to include as much detail as possible. any advice would be much appreciated. thankyou, James.
p.s if photos would help i can provide these as soon as i get a chance.
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