WatchDragon:im digging up this thread, my R12 popped, but the path onthe board is blackened, not the resistor itself, the pathway isnt damaged at all, its jsut black, could this resistor be bad without showing any damage?
Oh, and yes, the resistor can absolutly be bad without showing any external signs. In fact, it's pretty rare to be able to just look at most small components and tell if they are bad. R26 is completely open on my board, but barely looks scorched, R12 looks much worse and is barely out of tollerance. The scorcing is not what you should be concerned with. The majority of the scorcing and discolleration you will see on boards is caused by the plastic like protective coating that most boards are coated with simply heating up and changing color, or mildly scorcing. It's very rare for a foil run on the board to heat up enough to melt (have never seen it happen in all my years as a Navy electronics tech).
I actually used to joke that I could tell about how old the circuits cards in some of the radios on the ship were due to their color. When I put them in the would be a nice bright shiny green, and a couple years later, dull brown.But those thing operated under some pretty rough conditions.
I'm definatly going to try to modify the sub enclosure to disipate heat a little better, hopefully without making it sound like a wet fart.