Envelope-to: dave@picks.force9.co.uk Delivery-date: Fri, 03 Feb 2006 01:03:50 +0000 Received: by ptb-mxcore01.plus.net with spam-scanned (PlusNet MXCore v2.00) id 1F4pMb-0003ws-0O for dave@picks.force9.co.uk; Fri, 03 Feb 2006 01:03:50 +0000 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore01.plus.net with esmtp (PlusNet MXCore v2.00) id 1F4pMa-0003wd-Q7 for dave@picks.force9.co.uk; Fri, 03 Feb 2006 01:03:48 +0000 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1F4pMI-00084o-KY for rs_out_1@blacksheep.org; Fri, 03 Feb 2006 01:03:30 +0000 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1F4pMH-00084f-VQ for rsgb_lf_group@blacksheep.org; Fri, 03 Feb 2006 01:03:29 +0000 Received: from smtp808.mail.ukl.yahoo.com ([217.12.12.198]) by relay1.thorcom.net with smtp (Exim 4.51) id 1F4qgO-0006og-7O for rsgb_lf_group@blacksheep.org; Fri, 03 Feb 2006 02:28:39 +0000 Received: (qmail 4955 invoked from network); 3 Feb 2006 01:03:10 -0000 Received: from unknown (HELO lark) (alan.melia@btinternet.com@213.122.22.243 with login) by smtp808.mail.ukl.yahoo.com with SMTP; 3 Feb 2006 01:03:08 -0000 Message-ID: <002401c6285d$99138260$67b0fea9@lark> From: "Alan Melia" To: rsgb_lf_group@blacksheep.org References: <020220062310.23359.43E2915A00063CBB00005B3F22007358340B97010D0A020E06979D0E03@comcast.net> Date: Fri, 3 Feb 2006 00:54:59 -0000 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 5.00.2615.200 X-MimeOLE: Produced By Microsoft MimeOLE V5.00.2615.200 Subject: Re: 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) Hi Warren, an excursion to high temperature should not affect the ferrite as this is sintered at quite high temperatures to make the ring. What might suffer is the epoxy (usually) coating which may burn up and created a lossy shorted turn (guess, I have no experience of this) A quick solution might be to bung it in a beaker of cooking oil !! That will act as insulation as well !! Just think you could be the first station with an oil cooled antenna transformer !! Cheers de Alan G3NYK ----- Original Message ----- From: Warren K2ORS/WD2XGJ To: Sent: 02 February 2006 23:10 Subject: Re: LF: Re: Keeping the smoke in > Hi Mike, > > I don't think that the cores were damaged from the last incident. I was able to run the 250 watt transmitter through it with no problem and no measureable reflected power. I understand that Laurence also used 3 stacked FT-290-77s but actively cooled it. A cooling fan is not easy to do in my case since the tuner is in a weathertight box. > > -- > 73 Warren K2ORS/WD2XGJ > FN42hi > http://www.w4dex.com/wd2xgj.htm > > -------------- Original message ---------------------- > From: "MIKE REID" > > 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 > > > > > > > >