Return-Path: Received: (qmail 22533 invoked from network); 22 Jan 2004 19:55:56 -0000 Received: from unknown (HELO ptb-mxscan01.plus.net) (212.159.14.235) by mailstore with SMTP; 22 Jan 2004 19:55:56 -0000 Received: (qmail 74264 invoked from network); 22 Jan 2004 19:55:55 -0000 X-Filtered-by: Plusnet (hmail v1.01) X-Spam-detection-level: 11 Received: from ptb-mxcore01.plus.net (212.159.14.215) by ptb-mxscan01.plus.net with SMTP; 22 Jan 2004 19:55:54 -0000 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore01.plus.net with esmtp (Exim) id 1Ajkvi-000JBr-IE for dave@picks.force9.co.uk; Thu, 22 Jan 2004 19:55:54 +0000 X-Fake-Domain: majordom Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1AjkuS-0007kr-Ma for rs_out@blacksheep.org; Thu, 22 Jan 2004 19:54:36 +0000 Received: from [62.253.164.41] (helo=mta1-svc.business.ntl.com) by post.thorcom.com with esmtp (Exim 4.14) id 1AjkuS-0007kg-4V for rsgb_lf_group@blacksheep.org; Thu, 22 Jan 2004 19:54:36 +0000 X-Fake-Domain: l8p8y6 Received: from l8p8y6 ([62.252.232.58]) by mta1-svc.business.ntl.com (InterMail vM.4.01.03.37 201-229-121-137-20020806) with SMTP id <20040122195435.HILL12372.mta1-svc.business.ntl.com@l8p8y6> for ; Thu, 22 Jan 2004 19:54:35 +0000 X-Bad-Message-ID: no DNS (l8p8y6) Message-ID: <000201c3e0e1$dcea1e60$3ae8fc3e@l8p8y6> From: "hamilton mal" To: rsgb_lf_group@blacksheep.org References: <000c01c3e02e$600a21a0$01eafc3e@l8p8y6> <006801c3e102$8c730c00$6633f7c2@johnb5a82ea1a4> Date: Thu, 22 Jan 2004 12:15:11 -0000 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 5.50.4807.1700 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Subject: LF: Re: Re: SOFT START Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Checker-Version: SpamAssassin 2.60 (1.212-2003-09-23-exp) on post.thorcom.com X-Spam-Status: No, hits=0.6 required=5.0 tests=DATE_IN_PAST_06_12 autolearn=no version=2.60 X-SA-Exim-Scanned: Yes Sender: Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false X-PN-SPAMFiltered: yes X-Spam-Rating: 2 ----- Original Message ----- From: "John Rabson" To: Sent: Thursday, January 22, 2004 4:11 PM Subject: LF: Re: SOFT START > It's when a bank of capacitors totalling a quarter of a Farad at 24 volts is > connected with wrong polarity that things start to get spectacular. How could that happen, impossible except the constructor had too much GLENGARRAGCT Mc NAHT > > 73 > John G3PAI > > ----- Original Message ----- > From: "hamilton mal" > To: > Sent: Wednesday, January 21, 2004 2:53 PM > Subject: LF: SOFT START > > > Hi All > Surprisingly, most high power amps do not have a SOFT START, and judging by > the thump at times on switch on, it is even more surprising that the power > supply does not explode. In recent times I use a variac and gradually adjust > it to full voltages. > This is overkill and a more simple cct would suffice. I lost one mains > transformer a few years ago and the replacement cost more than the amp was > worth. Some of the PSU'S for low voltage high current FET AMPS used in LF > applications are even more vunerable ie 12 - 24 V at 20 - 100 A. Most > Amateurs that I have spoken to do not realize the danger involved. One of > the bean can size electrolytics 200 mfd capacity exploding would be like > firing a mortar, probably demolish the house in some cases. The stone built > country house would probably survive.If you are dabbling with QRP there is > no need to worry. > > 73 de Mal/G3KEV > > > > >