--- In
Homebrew_PCBs@yahoogroups.com, "James" <jamesrsweet@...> wrote:
>
>
>
> --- In Homebrew_PCBs@yahoogroups.com, "awakephd" <a_wake@> wrote:
> >
> > I'm not sure what the big deal is about printed-on fuses. I've done that many times -- in fact just the other day, when I made a bone-headed connection on the 170V PWM motor control board I was working on, several traces turned into instant fuses!
> >
> > I'm embarrassed to confess that I forgot that the "ground" on the board was NOT at the level of ground in the wall when I attached the ground lead from the o-scope. Fortunately the board "fused" rather than the o-scope. It destroyed two IC's on the board in the process, but that was a small price to pay compared to fixing or replacing the scope!
> >
> > And yes ... the board went in the trash and I started over -- much more carefully this time! And yes, the new board works perfectly.
> >
> >
>
>
> Been there, done that. ∗ALWAYS∗ use an isolation transformer when testing "hot chassis" equipment. It may save some expensive test gear, or yourself! If you don't have one, it can be made in a pinch with a pair of back to back power transformers.
>
I'm glad I'm not the only one. I had intended to test the board out feeding in power to the logic section from an isolated power source (and that is what I did after I re-made the board). But I had had to set the project aside for several weeks, so I when I finally got back to it I was overly eager ... and it was late, and I was tired, and I wasn't thinking. But hopefully the lesson is now burned into my brain! Errr ... no pun intended. :)