Nope. The cap was cool because the thing was shorted and had no voltage across it. Power is V * I.
As I said before, either an open or a short circuited component dissipates no power. The defective component is NOT always the hot one. A hot component is only a pointer to the fault, not necessarily the problem itself. This is especially true of fuses. Always ask "Why did the fuse blow??" -John ================= > I just tracked down a shorted tantalum in a Tektronix DM501 > multimeter. It was on the output of the floating -12 volt supply > bridge rectifier before the regulator. The current level was so low > that it never heated up although I burned two fingers on the push-pull > output transistors for the floating supply. The regulator is on a > separate module but the supply was still shorted when I pulled it and > the bad tantalum was the only part left. > > I have not seen a shorted tantalum before where it could not be surge > current related until now. > > On Sat, 24 Mar 2012 00:08:12 -0400, Peter Gottlieb <[email protected]> > wrote: > >>I had a HP 3326 which had a power supply in foldback. All the modules are >> inaccessible unless you have a rather rare set of extenders anyway. The >> voltmeter method quickly led me to the board and a bench supply and meter >> again to the shorted cap. Very easy. Other times I've borrowed the FLIR >> camera from work, also taught the new EEs that trick as well. It is a >> true lifesaver on dense surface mount boards. I haven't tried the liquid >> crystal sheet but it seems like an interesting idea so long as everything >> is about the same height. >> >> >>Peter >> >>On Mar 23, 2012, at 11:53 PM, [email protected] wrote: >> >>> Prior to emission or IR microscope technology, liquid crystals was how >>> you found hotspots on ICs. I've done this with a goop that you dispense >>> with a syringe. >>> >>> One trick to make this more sensitive is you bring a soldering iron >>> close to the liquid crystals. Not so close as to cause a change, but >>> you get them closer to the phase change point. >>> >>> >>> -----Original Message----- >>> From: Skip Withrow <[email protected]> >>> Sender: [email protected] >>> Date: Fri, 23 Mar 2012 21:07:45 >>> To: <[email protected]> >>> Reply-To: [email protected], >>> Discussion of precise time and frequency measurement >>> <[email protected]> >>> Subject: [time-nuts] Anyone familiar with SR-620 repair? >>> >>> You don't need expensive test equipment to find this kind of problem. >>> What >>> I use is a sheet of liquid crystal film with a transition temperature >>> just >>> slightly above your room temperature. Just lay it on the circuit board >>> and >>> you can find where the power is being dissipated (even if pretty small) >>> by >>> watching the colors change. >>> >>> I think Omega Engineering sells a 8.5" x 11" sheet for about $18 if >>> memory >>> serves me. I have used this trick many times and it works great to >>> find >>> shorted (bypass) caps. No disconnecting anything, no milliohm meters, >>> no 4 >>> or 5 digit voltmeters. > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
