HELP power transisors leaking dark brown goo!

[theOracle]

This is actually inside of a car ECU, which isn't a TV, but I figured you guys have seen everything!

I was going to replace the capacitors in a malfunctioning Toyota ECU, which is a normal thing I do, but was surprised to find, rather than leaking capacitors, two NEC 2SC4554 silicon power transistors had oozed a very dark brown goo all over the circuit board below them, much like a leaking capacitor would.

Has anyone ever seen something like this before and does this mean they are bad?

PS - the only replacement I can find is Renesas 2SC4554-AZ

will that work?




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[budm]

Re: HELP power transisors leaking dark brown goo!

Can we see the pictures? Did you make any test using the meter to see what you get?

[cashkennedy]

Re: HELP power transisors leaking dark brown goo!

Often parts are cooled by a oil that is non conductive. (often in high end radio amplifiers in cars) I would assume that's what has leaked out, and the parts that used to be cooled by oil are now not being cooled and will have burnt up. (Theyre not so much cooled as the oil is acting as a heatsink)

[theOracle]

Re: HELP power transisors leaking dark brown goo!

what is weird is that these appear to be in a normal TO-220F molded case.






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[cashkennedy]

Re: HELP power transisors leaking dark brown goo!

Yeah that is weird then. Are you sure its not just brown adhesive they used to hold parts in place while the board was soldered?

[theOracle]

Re: HELP power transisors leaking dark brown goo!

no, there is a huge mess of it, like something really leaked and had a major issue on this board, reminds me a lot of a badly leaking cap, except no electrolytics nearby





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[tw2005]

Re: HELP power transisors leaking dark brown goo!

Where this is mounted in the car is it possible for something to leak into the internals of the ECU like maybe a heater core?

once you post some photos it'll probably be a lot easier for someone to work it out.

[lexwalker]

Re: HELP power transisors leaking dark brown goo!

no, there is a huge mess of it, like something really leaked and had a major issue on this board, reminds me a lot of a badly leaking cap, except no electrolytics nearby

Could be leftover solder paste or flux. Those can look like brownish goo too...

[theOracle]

Re: HELP power transisors leaking dark brown goo!

this is practically black, like a burned area, but I have no good camera to photograph it with





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[ben7]

Re: HELP power transisors leaking dark brown goo!

Does it smell? Is it shiny, or dull? I've seen goo from popped semiconductors before (shiny, and a bit smelly, an odd unusual smell), I believe it is from melted plastic.