Envelope-to: dave@picks.force9.co.uk Delivery-date: Fri, 03 Feb 2006 00:45:40 +0000 Received: by ptb-mxcore01.plus.net with spam-scanned (PlusNet MXCore v2.00) id 1F4p4y-0004mt-TT for dave@picks.force9.co.uk; Fri, 03 Feb 2006 00:45:40 +0000 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore01.plus.net with esmtp (PlusNet MXCore v2.00) id 1F4p4y-0004eL-OV for dave@picks.force9.co.uk; Fri, 03 Feb 2006 00:45:36 +0000 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1F4p3z-0007wT-La for rs_out_1@blacksheep.org; Fri, 03 Feb 2006 00:44:35 +0000 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1F4p3z-0007wK-6w for rsgb_lf_group@blacksheep.org; Fri, 03 Feb 2006 00:44:35 +0000 Received: from defout.telus.net ([204.209.205.55] helo=priv-edmwes25.telusplanet.net) by relay1.thorcom.net with esmtp (Exim 4.51) id 1F4qO6-0006e8-47 for rsgb_lf_group@blacksheep.org; Fri, 03 Feb 2006 02:09:44 +0000 Received: from cognizant1 ([64.180.173.28]) by priv-edmwes25.telusplanet.net (InterMail vM.6.01.05.04 201-2131-123-105-20051025) with SMTP id <20060203004409.JQGA1229.priv-edmwes25.telusplanet.net@cognizant1> for ; Thu, 2 Feb 2006 17:44:09 -0700 Message-ID: <000d01c6285b$200b8a40$0201a8c0@private.network> From: "Scott Tilley" To: rsgb_lf_group@blacksheep.org References: <020220062241.29124.43E28A95000E876A000071C422007358340B97010D0A020E06979D0E03@comcast.net> Date: Thu, 2 Feb 2006 16:45:26 -0800 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1106 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Subject: LF: Re: Keeping the smoke in Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Transfer-Encoding: 8bit X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false X-PN-SpamFiltered: by PlusNet MXCore (v2.00) Contact G0MRF and get some of those big honk'n 58mm 3C90 toroid ( Suitable for tx matching transformer or antenna matching to 800W) £7.80 - Back in stock from 7/Jan/04 We use these and they rock. 73 Scott ----- Original Message ----- From: "Warren K2ORS/WD2XGJ" To: "rsgb lf reflector" Cc: "LWCA LF Reflector" Sent: Thursday, February 02, 2006 2:41 PM Subject: LF: Keeping the smoke in > Hello the list, > > I've heard that the secret to keeping things going in electronics is to make sure you don't let the smoke out (that's what makes it all work apparently). > > I have again failed to do so. After rewinding my toroidal loop transformer in the ATU, I had a core overheating problem. The core is 3 stacked FT-290-77 ferrites. > After setting the Decca up on QRSS for an hour or so I noticed a problem with the rf output current, it was pulsing up and down as if the Decca guard circuit was cutting in to protect the PA. So I through the breaker and went out and opened the tuner box. Smoke poured out. Bad news. I checked the temperatures with a non-contact infra-red thermometer and the toroid core was 343 Farenheit. The Curie temperature for type 77 ferrite is 200 C (which is 392 Farenheit). Not sure yet if the core is permanently damaged, I'm still waiting for it to cool down. > > All credit to Laurence who managed to get a loop to work at this power level! And especially with the currents he dealt with in the parallel wire loop configuration. > > I guess I need a bigger core than the 3 stacked FT-290-77s any suggestions out there? > > -- > 73 Warren K2ORS/WD2XGJ > FN42hi > http://www.w4dex.com/wd2xgj.htm >