Overloaded Horrible Antec SmartPower SP-500 to death
I don't think I need to introduce this power supply, as it has been featured in this forum before. I'd like to share what happened to mine. I am new to electronics and maybe someone will help me understand how this works.
The PSU was bought new and ran for years with its bad caps. Then, I decided to try overloading it. I added 20-25 amperes of 12 volt load. This ran okay for several months and the PSU began to shutdown under such load.
I looked inside, found the Fuhjyyu that everyone loves (except at the 12v filter, it was a different brand that nobody here likes, but was the only large cap that tested near rating on little Fluke meter.) They looked and tested as you expect, all electrolytics were replaced. At this time I noticed the burning around the optoisolator, I guess this is the 5vsb area.
I also dropped a dab of solder over the thermistor that controls the fans. Whee! The PSU ran again, no more hissing, even with the horrible overload. I ran it again for some more months. It stopped working with the heavy load, so I took the horrible load off, and then several months later, it died with a normal load. I reduced the load yet again and it ran for several hours and died again. Now it will not support a useful load.
Opening the PSU this time I noticed a new burn mark around the 12v output. Seems a jumper has changed color through some kind of metallurgic process unknown to me. The capacitor and inductor are OK.
I took the heatsinks out and as far as I can test with my little fluke meter I don't see anything wrong with the big devices there. The big diodes test all the same. The big bipolar transistors test as has been described they should on the diode tester, and I can use the ohmmeter to charge the gate of the FET and see it turns on. To me this proves they are acting reasonably like any device of their type and not that they will perform well. In other words, I believe that they are transistors.
When I first saw the burn mark by the optoisolator I figured it was a symptom of the bad caps -- these 5vsb filters have gotten attention here before -- and that it would not burn anymore having rectified "the problem." I didn't make any photographs at that time, so I'm not certain that the burn hasn't grown. Now, here is where I know I am over my head. I think I want to find out why this burned. Seems the neighbors of this opto are the transformer, surfacemount transistor and zener and a few passives around. But it seems the closest part to the evidence of the heat is the opto. Why would this get hot? Duty cycle too long, or too much current? Transformer is ruined? Looks like this could end up driving the FET.
Is there a schematic floating around of this or another Channel Well supply so that I might try to understand better? I'm thinking that I want to reassemble it and observe it on the bench with some load I can control, and maybe I will get a clue. But I also am not sure if I should remove any more components to test them out of circuit.
Thanks for reading. Hope you enjoyed this story, and I'm grateful for comments.
The PSU was bought new and ran for years with its bad caps. Then, I decided to try overloading it. I added 20-25 amperes of 12 volt load. This ran okay for several months and the PSU began to shutdown under such load.
I looked inside, found the Fuhjyyu that everyone loves (except at the 12v filter, it was a different brand that nobody here likes, but was the only large cap that tested near rating on little Fluke meter.) They looked and tested as you expect, all electrolytics were replaced. At this time I noticed the burning around the optoisolator, I guess this is the 5vsb area.
I also dropped a dab of solder over the thermistor that controls the fans. Whee! The PSU ran again, no more hissing, even with the horrible overload. I ran it again for some more months. It stopped working with the heavy load, so I took the horrible load off, and then several months later, it died with a normal load. I reduced the load yet again and it ran for several hours and died again. Now it will not support a useful load.
Opening the PSU this time I noticed a new burn mark around the 12v output. Seems a jumper has changed color through some kind of metallurgic process unknown to me. The capacitor and inductor are OK.
I took the heatsinks out and as far as I can test with my little fluke meter I don't see anything wrong with the big devices there. The big diodes test all the same. The big bipolar transistors test as has been described they should on the diode tester, and I can use the ohmmeter to charge the gate of the FET and see it turns on. To me this proves they are acting reasonably like any device of their type and not that they will perform well. In other words, I believe that they are transistors.
When I first saw the burn mark by the optoisolator I figured it was a symptom of the bad caps -- these 5vsb filters have gotten attention here before -- and that it would not burn anymore having rectified "the problem." I didn't make any photographs at that time, so I'm not certain that the burn hasn't grown. Now, here is where I know I am over my head. I think I want to find out why this burned. Seems the neighbors of this opto are the transformer, surfacemount transistor and zener and a few passives around. But it seems the closest part to the evidence of the heat is the opto. Why would this get hot? Duty cycle too long, or too much current? Transformer is ruined? Looks like this could end up driving the FET.
Is there a schematic floating around of this or another Channel Well supply so that I might try to understand better? I'm thinking that I want to reassemble it and observe it on the bench with some load I can control, and maybe I will get a clue. But I also am not sure if I should remove any more components to test them out of circuit.
Thanks for reading. Hope you enjoyed this story, and I'm grateful for comments.
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