Return-Path: Received: from rly-db08.mx.aol.com (rly-db08.mail.aol.com [172.19.130.83]) by air-db05.mail.aol.com (v124.15) with ESMTP id MAILINDB052-ae14a3c9a991d1; Sat, 20 Jun 2009 04:15:41 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by rly-db08.mx.aol.com (v124.15) with ESMTP id MAILRELAYINDB087-ae14a3c9a991d1; Sat, 20 Jun 2009 04:15:25 -0400 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1MHviY-000365-66 for rs_out_1@blacksheep.org; Sat, 20 Jun 2009 09:14:30 +0100 Received: from [83.244.159.144] (helo=relay3.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1MHviX-00035w-NF for rsgb_lf_group@blacksheep.org; Sat, 20 Jun 2009 09:14:29 +0100 Received: from ttsmtp-3.cpwnetworks.com ([62.24.128.244] helo=ttsmtp.cpwnetworks.com) by relay3.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1MHviW-00036J-A2 for rsgb_lf_group@blacksheep.org; Sat, 20 Jun 2009 09:14:30 +0100 X-Path: TalkTalk-smtp X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AqYEAJ83PEpcG76K/2dsb2JhbACCJy2CC4dwwUSCSIFBBQ Received: from unknown (HELO mal769a60aa920) ([92.27.190.138]) by ttsmtp.cpwnetworks.com with SMTP; 20 Jun 2009 09:14:09 +0100 Message-ID: <000a01c9f17f$16506d40$0301a8c0@mal769a60aa920> From: "mal hamilton" To: References: <582241.74739.qm@web28516.mail.ukl.yahoo.com> Date: Sat, 20 Jun 2009 09:14:08 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2180 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: LF: Re: 500 kHz - Fans Content-Type: multipart/alternative; boundary="----=_NextPart_000_0007_01C9F187.77C88A00" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.5 required=5.0 tests=HTML_40_50,HTML_MESSAGE autolearn=no version=2.63 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-AOL-IP: 193.82.116.20 ------=_NextPart_000_0007_01C9F187.77C88A00 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Chris Use a separate pwr supply for the fan, not the same supply that runs the FET= S or driver ccts. This is what I do and never had a problem. mal/g3kev ----- Original Message -----=20 From: Chris Osborn=20 To: LF Group=20 Sent: Saturday, June 20, 2009 7:34 AM Subject: LF: 500 kHz - Fans LF, I've nearly completed my new PA for 500 kHz and have now managed to stop destroying FET's. Unfortunately I have an unusual problem in that the heatsink cooling fans are going U/S. I have used 24 volts brushless PC-type fans and after a while they either die completely or start to go backwards slowly. . . The fans may be slightly over-run but only by a volt or so and on key-up=20 (unregulated supply) and are situated about 50 mm (2 inches) from the heat= sink. I have rf decoupled them from the supply but maybe not well enough ! Any suggestions in curing this problem would be most welcome. 73 Chris G3XIZ ------=_NextPart_000_0007_01C9F187.77C88A00 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

Chris

Use a separate pwr supply for the fan, not=20= the same=20 supply that runs the FETS or driver ccts. This is what I do and never had a=20 problem.

mal/g3kev

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

Chris Osbor= n=20

To: LF Group
Sent: Saturday, June 20, 2009 7:34=20 AM

Subject: LF: 500 kHz - Fans

LF,

I've nearly completed my new PA for 500 kHz and have now managed to
stop destroying FET's.

Unfortunately I have an unusual problem in that the heatsink cooling=20 fans

are going U/S.

I have used 24 volts brushless PC-type fans and after a while they
either die completely or start to go backwards slowly. . .

The fans may be slightly over-run but only by a volt or so and on key= -up=20

(unregulated supply) and are situated about 50 mm (2 inches) from the= =20 heatsink.

I have rf decoupled them from the supply but maybe not well enou= gh=20 !

Any suggestions in curing this problem would be most welcome.

73 Chris G3XIZ

------=_NextPart_000_0007_01C9F187.77C88A00--