Lightning vs Intellitouch

[ogdento]

I've been fixing an intellitouch mainboard that was involved in a lightning strike and I thought it was interesting enough to share...

I've only ever seen lightning damage the comm ports - but on this board it blew out rectifier BR2 (for the 12vac input), inductor L1 (between that rectifier's output and the 5v regulator), and most strangely it burst buffer ic U10 (a 74hc244d that connects the micro to the relay drivers).

There was no power to the board, but after about an hour I got it to boot up and take the latest firmware. I have to replace the buffer ic before I know if it will actually control anything but I was shocked to see that it worked at all. Even more shocking was that the comm ports are fine and it can talk to my indoor controller!

In this pic, I've replaced rectifier BR2 (leftmost yellow circle), and temporarily substituted a copper wire for inductor L1 (rightmost circle) while I wait for my Mouser order. I removed the ULN2803 relay drivers to test them - they were all fine.




Here you can see inductor L1... the wire burned up and the case cracked:




Here is a shot of buffer ic U10 after removal... it burst open on the top, split open along the pins, and its guts have oozed out:



I think it's been said on TFP before, but if you live in a lightning prone region a lightning suppressor is a good investment!

 

[Jimrahbe]

Tom,

I believe that it really matters where the lightning enters the card...

In my case, it came in on the com port wire between the ET and the house... On the card you have I would suspect it came in on the AC power line..

In a past life, I worked with really high end audio visual stuff and we were all the time getting things back that had been damaged by lightning. In almost every case the site had remote buildings with com lines between the remote units and the main units.. Rarely did we see a direct hit on the power line... On the few we did see, it would either blow a hole in the top of the chips or in a few cases blow the entire top off the chip.. Com ports tended to just quick working and maybe change color..

Thanks for the pics..

Jim R.

 

[ogdento]

Absolutely right Jim, what you described has been my experience as well... with the lightning striking something other than power. Antennas, comm lines, network wires etc. Years ago a friend ran a cat-5 cable on the exterior of his house from the 1st to 2nd floor... a lightning strike blew up a switch and a couple of network cards.

On the 74HC244 in the pic above, there's a dark spot between the "2" in the 74HC244D label and the "Q" in the AQ796... the top didn't quite pop off (that would be crazy to see!) but there's a decent bulge and crack there where the guts came up through

 

[Jimrahbe]

Tom,

I suspect chips are made much better today... My experience is from many years ago when chips were made by scraping two stones together...

Jim R.