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Forum Index : Electronics : repair section
| Author | Message | ||||
| brucedownunder2 Guru  Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
I was googling through for any knowledge on repairing W7 powerstar inverters.. I came across this interesting topic on repair of the power section board. I do hope the author is happy for my posting it ?. the link is this , quan-diy.com/misc/inverters/powerstar.htm someone more savvy may like to tidy that link up ,I'm fairly dumb at these things. I'm wondering , do you think there would be a section ,here,on the forum ,for repair postings ? I reckon there would be a lot of interest in almost everything from correct soldering to welding to electronics problem solving ,under this sort of heading -what do you think . keep them all in one section ,rather having them scattered thoughout. I'd still keep long postings going like Marks inverter and Phills ongoing builds . but this section should be short descriptions on how someone fixed something within those stories. Bruce Bruce Bushboy |
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Chopperp Guru Joined: 03/01/2018 Location: AustraliaPosts: 1057 |
W7 Link I'd be interested in a repair section ChopperP |
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| brucedownunder2 Guru Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
Thanks Chopper, not all that silly ,really . Most of the stuff here is what Mark and Oz and others have used to build their inverter of today. The guy bought up a very interesting point ,when he pointed out that there was no heat transfer gunk on the mosfets to the heatsink ? . that alone is worth noting. In an example like this , one of our tech friends could also ,maybe , insert voltages,resistance, Etc to expect at some of these component points??. Thats a pet hate of mine ,these days, nothing on the schematic drawings,if you can get one ,that is?? Bruce Bushboy |
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Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
There was no blobs of heat transfer gunk under the MOSFETs for a reason. They need to make good electrical contact with the heatsink as their drains use the heatsink as electrical conduct as well as to conduct heat. Putting thermal transfer grease will increase resistance and cause more heat. My Inverter can run at 8KW for 30 minutes and well above that for shorter periods of time and it has no thermal grease. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| brucedownunder2 Guru Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
Oh, thanks for that Madness,not so mad ,after all ?. Makes sense, so the gunk is really an insulator ,not an electrical conductor ,even though it transfers heat ? Do they(manufacturers) tell us this on the container ,betcha no ?. ok, so the heat transfer paste is mostly for heat -generated components that rely on dissapation of heat ,rather than conduction of an electrical path?. Good point in bringing this up ,betcha 90% don,t know that? Bruce Bushboy |
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| Solar Mike Guru Joined: 08/02/2015 Location: New ZealandPosts: 1138 |
I have discovered the back (Drain) of many of the cheap Chinese mosfets are not very flat, and make very poor contact with the flat alloy heat sink. Place a metal rule as a straight edge across the back of each mosfet and hold it up to the light, if you can see light shining under, then it will have poor heat transfer and uneven current contact, resulting in hot spots and possibly destruction for no apparent reason. This can be fixed by gently lapping them on a sheet of 600 emery paper on a flat surface (thick glass) with kero lubricant, only takes 30 seconds or so, a very thin smear of petroleum jelly is all that is required to keep any exposed copper from oxidizing if the tin coating is worn though. As Madness says, heat sink gunk should not be used here, it only makes things worse. Cheers Mike |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
I have tried lapping the HY4008W MOSFETs that I use and found they are quite flat already. I have various grades of wet and dry paper glued to glass with spray adhesive that I use for sharpening chisels and knives. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
I think a decent thick washer under the screw head would exert enough pressure for a good contact with the back plane. Its what I do anyway... Just relying on the screw head may introduce too concentrated contact pressure just around the screw hole. Klaus |
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| Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
If there was a blob of tin or simply just not flat lapping would make a big difference trying to correct it with any other means would not help. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
Tutorials are a bit of a dilemma, I cant stuff 30 years of experience and learned skill about a specialist subject into one post if the question that is asked is not specific. The more you know about a subject the harder it gets. On the other hand, there is stuff I know now that I wish I could have found out much earlier in my life. The basic fundamentals of how something actually works, not the BS "common sense" that we swallow as fact. I dont know, I have several topics half written that I just cant finish, the wording to get across a concept without any misunderstanding is very difficult. I'm confused, no wait... maybe I'm not... |
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