B-O-O-M-!!! (the culprit is discovered)

[johnridley]

This evening I went to address the fact that the dog's contain collar hasn't worked for a while. I replaced the battery and went to test it since it didn't seem like the old battery was in that bad a shape. Didn't work. So I went to the garage to check on the transmitter. Pilot light was out. Checked and found that the transformer wasn't plugged into the wall. Dug around and found it on the floor, with the plastic case off and the wires all chewed up. OK, some rodent likes wires.

Went inside to show J and to try to find a replacement wall-wart. Then realized, "that doesn't look like chewing. Actually, that looks a lot like the windings exploded." Went and got the transmitter box; it rattled.

It's been about 2 months since we got our close lighting strike; I think now we know what it hit; it must have hit the wire loop that the dog's collar runs on. The inside of the transmitter that's hooked to that loop is covered with black soot, a toroid was blown right off the board, the controller chip has a crater in it, and the transformer has the above mentioned damage. Check it out. I think this is the probable entry point for a big ole' spike.

Comments

[johnridley.livejournal.com]

yeah, the way the windings were ripped apart, it really looks to me like they were pulled apart by their own magnetic field. That's a HUGE pulse, like the kind of thing you get in a quarter-shrinker. I think it's likely that it was able to induce several hundred volts on the mains side even against the load on that side.

[erikvolson.livejournal.com]

Looking at the damage, I think it came in the power side -- it looks like the power input is the jack on the right side of that pic, right. The traces on the loop plug look fine, but all the stuff near the power input is dead several ways.

I amused that the toroid was able to eject before going down in flames....

[johnridley.livejournal.com]

Nope, the blown apart bit on the top is the secondary. The terminals you see on the bottom lead to much thinner wires that you can barely make out that lead to the winding that's still intact.

[johnridley.livejournal.com]

I think that if the surge came in from the mains and caused this kind of damage, it would have exploded half the equipment in our house, rather than just minorly messing up a couple of mainboards.