Polymorph wrote:
On Feb 25, 10:04 am, Steven Hirsch <snhir...@gmail.com> wrote: <snip>Don't overlook the possibility of a bad solder joint! Sometimes one can get fooled when playing with freeze spray, particularly if there's a delayed reaction as the temperature change works its way through the PC board.Good idea! Thanks Steven. I'll try re-soldering both capacitors and see if the situation improves. I hadn't thought of that. I take it that under higher operating temps, a bad solder joint can open up?
A bad solder joint (or a hairline crack in a copper trace) can open under *any* change in condition! Pressing with a plastic tool to flex the board gently while observing the circuit's operation is a good way to localize such mechanical defects. BTW, if you use a narrow plastic tube with cooling spray, you can direct it much more selectively. Another technique is to clamp an alligator clip onto a lead of the suspect component, close to the component, then spray the clip in such a way that the overspray doesn't hit anything relevant. Heat conduction will then lower the temperature of that component quite selectively. -michael NadaPong: Network game demo for Apple II computers! Home page: http://members.aol.com/MJMahon/ "The wastebasket is our most important design tool--and it's seriously underused."