Envelope-to: dave@picks.force9.co.uk Delivery-date: Thu, 02 Feb 2006 22:49:43 +0000 Received: by ptb-mxcore01.plus.net with spam-scanned (PlusNet MXCore v2.00) id 1F4nGn-00076V-Hd for dave@picks.force9.co.uk; Thu, 02 Feb 2006 22:49:43 +0000 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore01.plus.net with esmtp (PlusNet MXCore v2.00) id 1F4nGn-00075t-9x for dave@picks.force9.co.uk; Thu, 02 Feb 2006 22:49:41 +0000 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1F4nGY-0007Gy-9R for rs_out_1@blacksheep.org; Thu, 02 Feb 2006 22:49:26 +0000 Received: from [193.82.59.130] (helo=relay2.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1F4nGX-0007Gp-KX for rsgb_lf_group@blacksheep.org; Thu, 02 Feb 2006 22:49:25 +0000 Received: from omc2-s32.bay6.hotmail.com ([65.54.249.42]) by relay2.thorcom.net with esmtp (Exim 4.51) id 1F4nz1-0006EV-M7 for rsgb_lf_group@blacksheep.org; Thu, 02 Feb 2006 23:35:25 +0000 Received: from hotmail.com ([65.54.172.112]) by omc2-s32.bay6.hotmail.com with Microsoft SMTPSVC(6.0.3790.211); Thu, 2 Feb 2006 14:49:15 -0800 Received: from mail pickup service by hotmail.com with Microsoft SMTPSVC; Thu, 2 Feb 2006 14:49:15 -0800 Message-ID: Received: from 71.37.244.7 by BAY5-DAV8.phx.gbl with DAV; Thu, 02 Feb 2006 22:49:12 +0000 X-Originating-IP: [71.37.244.7] X-Originating-Email: [we0h1@msn.com] X-Sender: we0h1@msn.com From: "MIKE REID" To: rsgb_lf_group@blacksheep.org References: <020220062241.29124.43E28A95000E876A000071C422007358340B97010D0A020E06979D0E03@comcast.net> Date: Thu, 2 Feb 2006 16:49:12 -0600 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: MSN 9 X-MIMEOLE: Produced By MSN MimeOLE V9.10.0011.1703 Seal-Send-Time: Thu, 2 Feb 2006 16:49:12 -0600 X-OriginalArrivalTime: 02 Feb 2006 22:49:15.0551 (UTC) FILETIME=[E4A77AF0:01C6284A] Subject: LF: Re: Keeping the smoke in Content-Type: text/html; charset=windows-1252 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) Content-transfer-encoding: 8bit

What cores did Laurence use and what wire size & type? Sorry to hear she failed again. Maybe the cores got damaged the other day with no external indications like cracking or? I don't recall you having trouble with the transformer when it was dry and Teflon is way better than cotton so that leads me to think the cores were no good after the first heat cycle/failure.

Mike

WE0H

----- Original Message -----

From: Warren K2ORS/WD2XGJ

To: rsgb lf reflector

Cc: LWCA LF Reflector

Sent: Thursday, February 02, 2006 4:41 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