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Exploding line drivers?


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Anyone seen this one before?

 

Got an SE logic board a while back which was sold as 'working except for a damaged MC3488'.  It did indeed work, and it did indeed have a damaged MC3488.

 

When I came to replace the MC3488, it turned out that it wasn't just damaged but must have actually exploded with some force; the case came off in three parts, leaving several of its legs behind, and underneath it, the solder mask was completely gone and the substrate was all toasty:

 

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And yet, nothing else seems to be damaged; I haven't checked the rest of the serial circuitry for issues, but it looks OK.

 

These line drivers drive the handshaking output lines on the serial ports, so all I can think of is that someone somehow managed to force mains voltage up the handshaking lines or something.

 

Anyone seen this before?  More curiosity than anything else :-)

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Now that sure is interesting, I would have thought the line drivers would more just melt in a puddle on an overcurrent overheat.  But that's silly upon further thought... it's not thermoplastic casing, it's epoxy.  So disintegration like cracking would be more likely than melting to liquid.

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On 4/6/2021 at 9:36 PM, History_SE30_Dude said:

Phone net and there was an active line on the two wires that it uses? Just a guess, that is 48v and can spike to 90v. I almost killed a IIvx as a kid, it smoked the adapter.

 

Oh, I hadn't thought of that!

 

23 hours ago, quorten said:

So disintegration like cracking would be more likely than melting to liquid.

 

Part of the chip basically fell to powder as I tried to lift it off the board, and I wasn't being rough!  I'm amazed this much damage was done to that one chip without really any damage around it, honestly.  It must have been quite dramatic when it went off

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