Laryn, If the power supply were a switching design, current foldback would occur. But, in the typical Astron RS-series linear supply, the firing of the SCR puts a bolted short on the output. As soon as the large capacitors on the output start to lose their charge, the regulator tries to maintain the output voltage by turning on the pass transistors to full conduction, quickly exceeding the current ratings of the transformer and rectifier diodes and blowing the fuse. Every time this has happened to an Astron RS supply (that I have personal knowledge of), it has blown the fuse. Every time. Odd that your experience is different. The fuse ratings are specified by Astron to ensure that they will blow under such conditions.
Because of their (RS-series) relative instability in high-RF environments, I now install only Duracomm, Samlex, and Astron switching power supplies. Lightweight, very efficient, and very reliable. 'Nuff said. 73, Eric Lemmon WB6FLY --- In Repeater-Builder@yahoogroups.com, "Laryn Lohman" <lar...@...> wrote: > > <snip> > > Why is the fuse blowing? Shouldn't the crowbar firing cause simple > current foldback? All of my Astrons do, and never blow fuses. > > My apologies if this has been brought up before... > > Laryn K8TVZ >
