68kMLA Supporter cheesestraws Posted April 6 68kMLA Supporter Report Share Posted April 6 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: \ 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 Quote Link to post Share on other sites
History_SE30_Dude Posted April 6 Report Share Posted April 6 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. Quote Link to post Share on other sites
quorten Posted April 7 Report Share Posted April 7 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. Quote Link to post Share on other sites
68kMLA Supporter cheesestraws Posted April 7 Author 68kMLA Supporter Report Share Posted April 7 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 Quote Link to post Share on other sites
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.