I should point out that Astron has made several significant changes to the RS-series regulator boards over the past 20 years, and that may explain why some Astron power supplies always blow the input fuse when shorted, while others never do. Every one of my own Astron linear power supplies is more than twenty years old, and all of them blow the input fuse when shorted by the SCR. Some posters report differing results, and that may be due to recent changes in the regulator board's design. For what it's worth, almost every Astron regulator board I've seen has a few extra resistors or capacitors added to it, as if each one was "customized" during manufacture. According to Fred, Astron's lead technician, some components are still being changed to make the units more stable- decades after the original design!
Here's one tip I learned a long time ago: Use exactly the fuse type and rating that Astron specifies for the specific power supply. Don't substitute a slow-blow fuse for a fast-blow, and don't use a higher-rated fuse or one that is intended for automotive use in place of one rated for 250 volts. If the correct fuse keeps blowing, there is a problem that should be found and fixed. Most Astron power supplies include an MOV (Metal Oxide Varistor) immediately downstream of the fuse. Such devices are usually rated for 130 VAC when applied on devices that operate at 120 VAC. If the line voltage is abnormally high, the MOV will get warm and become more likely to enter avalanche mode on modest spikes. Utilities are supposed to maintain the nominal utilization voltage at 120 VAC +/- 5%, so if the voltage ever exceeds 126 VAC, or falls below 114 VAC, it's time to complain to the electrical provider. 73, Eric Lemmon WB6FLY --- In Repeater-Builder@yahoogroups.com, "Adam T. Cately" <atcat...@...> wrote: > > At 07:38 AM 12/26/08 -0500, you wrote: > >That pretty much confirms my thinking. If the supply is blowing fuses, > something is actually wrong. The crowbar shouldn't cause it to happen. > > > Well... Yes and no... > > If the SCR fires, you dump all the available current through the supply > to ground, and the supply will blow the fuse - THAT is the designed re- > sponse so that you don't let it sit there and burn up. > > When you short the output - IF the current-sense circuitry is working > to spec, the supply sees the rise in current and shuts down the voltage to > alleviate the SCR from firing - again, THAT is what this circuit was > designed for. > > I always *assumed* the SCR was for over-voltage (shorted output pass > transistor) and the fold-back was for over-current, under regular output > conditions. > > If the supply blows the fuse, something IS wrong, but it IS DESIGNED to > do that when something is wrong, so... > > > > > > >Chuck > >WB2EDV > > > > > > > > ----- Original Message ----- > > From: william...@... > > To: Repeater-Builder@yahoogroups.com > > Sent: Thursday, December 25, 2008 11:41 PM > > Subject: Re: [Repeater-Builder] Re: Astron P/S question > > > > > > I have an Astron RM-35M (35Amp) that I just tested by shorting the output > and it doesn't blow the fuse. I think I would be looking for something in > the primary circuit that might be shorting like the transformer primary or > the surge arrestor or maybe the wiring. I have seen transformers that short > after they warm up a little. > > > > Bill - WA0CBW > > > > In a message dated 12/25/2008 10:11:11 P.M. Central Standard Time, > lar...@... writes: > > --- In Repeater-Builder@yahoogroups.com, "Chuck Kelsey" <wb2edv@> > > wrote: > > > > > > I have an old Bullet power supply built from a kit (anyone remember > > those?) > > > that uses the 723. You can short the output time and time again and it > > > simply folds back. > > > > > > heheheh I have one of those still in service on a repeater. Re-capped > > it a year ago and it still works fine. As I recall a shorted output > > simply folds back, like you say. > > > > I also have two Astrons here on the bench. One is a VS12, the other > > is a RS12. When the output is directly shorted with heavy wire they > > both simply fold back. Shorted them dozens of times; never a blown fuse. > > > > Laryn K8TVZ > > > > > > ------------------------------------ > > > > > > > > Yahoo! Groups Links > > > > > > > > > > > > > > > > > > > >------------------------------------------------------------------- ----------- > > Don't be the last to know - click here for the latest news that will have > people talking. > > > > > > > > > ><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> > ><HTML><HEAD> > ><META http-equiv=Content-Type content="text/html; charset=iso-8859- 1"> > ><META content="MSHTML 6.00.6000.16788" name=GENERATOR> > ><STYLE></STYLE> > ></HEAD> > ><BODY id=role_body style="FONT-SIZE: 10pt; COLOR: #000000; FONT- FAMILY: Arial" > >bottomMargin=7 bgColor=#ffffff leftMargin=7 topMargin=7 rightMargin=7> > > > > > ><DIV>That pretty much confirms my thinking. If the supply is blowing fuses, > >something is actually wrong. The crowbar shouldn't cause it to happen.</DIV> > ><DIV> </DIV> > ><DIV>Chuck</DIV> > ><DIV>WB2EDV</DIV> > ><DIV> </DIV> > ><DIV> </DIV> > ><DIV> </DIV> > ><BLOCKQUOTE > >style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; > BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px"> > > <DIV style="FONT: 10pt arial">----- Original Message ----- </DIV> > > <DIV > > style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: > black"><B>From:</B> > > <A title=william...@... > > href="mailto:william...@...";>william...@...</A> </DIV> > > <DIV style="FONT: 10pt arial"><B>To:</B> <A > > title=repeater-buil...@yahoogroups.com > > > href="mailto:Repeater-Builder@yahoogroups.com";>Repeater- buil...@yahoogroups. > com</A> > > </DIV> > > <DIV style="FONT: 10pt arial"><B>Sent:</B> Thursday, December 25, 2008 11:41 > > PM</DIV> > > <DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [Repeater- Builder] Re: > > Astron P/S question</DIV> > > <DIV><BR></DIV><FONT id=role_document face=Arial color=#000000 size=2> > > <DIV>I have an Astron RM-35M (35Amp) that I just tested by shorting the > output > > and it doesn't blow the fuse. I think I would be looking for something > > in the primary circuit that might be shorting like the transformer > primary or > > the surge arrestor or maybe the wiring. I have seen transformers that > > short after they warm up a little. </DIV> > > <DIV> </DIV> > > <DIV>Bill - WA0CBW</DIV> > > <DIV> </DIV> > > <DIV> > > <DIV>In a message dated 12/25/2008 10:11:11 P.M. Central Standard Time, > > lar...@... writes:</DIV> > > <BLOCKQUOTE > > style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: blue 2px > solid"><FONT > > style="BACKGROUND-COLOR: transparent" face=Arial color=#000000 > size=2>--- In > > Repeater-Builder@yahoogroups.com, "Chuck Kelsey" > > wb2edv@<BR>wrote:<BR>><BR>> I have an old Bullet power > > supply built from a kit (anyone remember<BR>those?) <BR>> that uses the > > 723. You can short the output time and time again and it <BR>> simply > > folds back.<BR><BR><BR>heheheh I have one of those still in service on a > > repeater. Re-capped<BR>it a year ago and it still works > fine. As > > I recall a shorted output<BR>simply folds back, like you say.<BR><BR>I > also > > have two Astrons here on the bench. One is a VS12, the other<BR>is a > > RS12. When the output is directly shorted with heavy wire > they<BR>both > > simply fold back. Shorted them dozens of times; never a blown > > fuse.<BR><BR>Laryn > > > K8TVZ<BR><BR><BR>------------------------------------ <BR><BR><BR><BR>Yahoo! > > Groups Links<BR><BR><*> To visit your group on the web, go > > to:<BR> > > http://groups.yahoo.com/group/Repeater- Builder/<BR><BR><*> Your > email > > settings:<BR> Individual Email | Traditional<BR><BR><*> > > To change settings online go to:<BR> > > http://groups.yahoo.com/group/Repeater-Builder/join<BR> > (Yahoo! > > ID required)<BR><BR><*> To change settings via email:<BR> > > > mailto:repeater-builder-dig...@yahoogroups.com <BR> > > mailto:Repeater-Builder- fullfeatu...@yahoogroups.com<BR><BR><*> To > > unsubscribe from this group, send an email to:<BR> > > repeater-builder-unsubscr...@yahoogroups.com<BR><BR><*> Your use of > > Yahoo! Groups is subject to:<BR> > > > http://docs.yahoo.com/info/terms/<BR><BR></FONT></BLOCKQUOTE></DIV></F ONT><B > R><BR><BR> > > <DIV class=aol_ad_footer id=91f6717888dc07af2808160c54342c2><FONT > > style="FONT: 10pt ARIAL, SAN-SERIF; COLOR: black"> > > <HR style="MARGIN-TOP: 10px"> > > Don't be the last to know - <A > > href="http://www.aol.com/?ncid=emlcntaolcom00000021";>click here<A> for the > > latest news that will have people talking.</FONT></DIV><SPAN > > style="COLOR: white" width="1"></SPAN> </BLOCKQUOTE> > ><span width="1" style="color: white;"/></span> > ></BODY></HTML> > > > > - Adam - >
