If still functional, the power supply regulator isn't "turned off", it still tries to supply some current* into the (nearly) short circuit SCR. At the same time the battery supplies current limited only by its internal impedance and the resistance of the interconnect.
* If I'm not mistaken (always a good possibility) the Astrons use foldback current limiting to limit the dissipation of the pass transistors. --- On Mon, 6/8/09, Ron D'Eau Claire <[email protected]> wrote: From: Ron D'Eau Claire <[email protected]> Subject: RE: [Elecraft] Battery Charging with DC Power Supply To: "'Wes Stewart'" <[email protected]>, "'Bill Miner'" <[email protected]>, [email protected] Date: Monday, June 8, 2009, 9:23 AM Tnx Wes! So the battery voltage across the power supply terminals keeps the SCR turned on, even though the supply voltage is turned off by the crowbar. That would surely lead to a dead SCR without a suitable fuse in the battery circuit. Ron AC7AC Since Astron has been mentioned in this thread, I'll use that as an example. The SCR that is part of the crowbar is connected directly across the output terminals of the supply. When used normally, the firing of the SCR shorts the output and the supply goes into current limit, if still functional, or hopefully blows the primary fuse if not. With a battery across the output, if the SCR fires, something is going to fuse. It will be either a user-installed external fuse or something else. It would probably not be a good idea to rely on the something else. Wes N7WS ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
