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1. [Amps] 3-500z - intermittent filament (score: 1): Author: <terry@g4amt.com>; Date: Tue, 6 Feb 2007 09:54:08 -0000; My TL922 is mis-behaving with one tube operating intermittently. Symptoms were of open circuit filament but valve tested ok with ohm-meter and worked when refitted. Next power up, tube failed to work; /archives//html/Amps/2007-02/msg00070.html (6,610 bytes)
2. Re: [Amps] 3-500z - intermittent filament (score: 1): Author: Martin Sole <msole@loxinfo.co.th>; Date: Tue, 06 Feb 2007 18:12:37 +0700; Hi Terry, I think you have experienced one or more not uncommon problems with a number of 3-500 amplifiers. The re-soldering of tubes base pins is a common sight and though highly inappropriate I thi; /archives//html/Amps/2007-02/msg00071.html (8,981 bytes)
3. Re: [Amps] 3-500z - intermittent filament (score: 1): Author: "Robert B. Bonner" <rbonner@qro.com>; Date: Tue, 6 Feb 2007 06:04:04 -0600; Martin, Terry, Group, Good morning guys. Like I have mentioned before when I was back at the RADIO SHOP (Drake Collins Kenwood, Yaesu etc factory service) while in college in the late 70's I had to p; /archives//html/Amps/2007-02/msg00072.html (11,879 bytes)
4. Re: [Amps] 3-500z - intermittent filament (score: 1): Author: Martin Sole <msole@loxinfo.co.th>; Date: Tue, 06 Feb 2007 23:08:31 +0700; I wonder, would it so happen that the mounting holes for the SK-410 might just be the same as those for the Johnson 275? I think real sockets might have made it on to my list for the Henry rebuild fi; /archives//html/Amps/2007-02/msg00077.html (14,378 bytes)
5. Re: [Amps] 3-500z - intermittent filament (score: 1): Author: "David G4FTC" <g4ftc@hotmail.com>; Date: Tue, 06 Feb 2007 17:11:06 +0000; From: "Robert B. Bonner" wrote Well the amplifiers where where air blew sideways across the tubes and pins instead of through the sockets or didn?t have enough airflow due to NOISE CONCERNS developed; /archives//html/Amps/2007-02/msg00082.html (8,906 bytes)
6. Re: [Amps] 3-500z - intermittent filament (score: 1): Author: Peter Chadwick <g3rzp@g3rzp.wanadoo.co.uk>; Date: Tue, 6 Feb 2007 18:17:59 +0100 (CET); The Mullard data sheet for the 4-250 and 4-400 equivalents (which have the same 5 volt, 14 amp filament as the 3-500Z) specifically call for a certain amount of cooling air over the socket pins. If y; /archives//html/Amps/2007-02/msg00084.html (7,843 bytes)
7. Re: [Amps] 3-500z - intermittent filament (score: 1): Author: Jay Musikar <af2c@yahoo.com>; Date: Wed, 7 Feb 2007 11:02:10 -0800 (PST); Actually - The problems with the filaments of the 3-500z tubes were NOT confined to the SB220 amps vack in the 1960 and 70 era. The problem also occurred in the Drake L-4B amps. The solder would lite; /archives//html/Amps/2007-02/msg00122.html (16,677 bytes)
8. Re: [Amps] 3-500z - intermittent filament (score: 1): Author: <terry@g4amt.com>; Date: Thu, 8 Feb 2007 11:18:58 -0000; Thank you to all who responded - lots been here before ! I have resoldered the filament pins of the valve and hopefully that has done the trick. Just a couple of observations - the 3-500z s are not m; /archives//html/Amps/2007-02/msg00127.html (9,590 bytes)
9. Re: [Amps] 3-500z - intermittent filament (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Thu, 08 Feb 2007 12:15:26 +0000; A question as to what should be used here? There's 'silver solder' as used with a torch for brazing. There's also standard pcb solders with added silver content to give them a lower melting point tha; /archives//html/Amps/2007-02/msg00128.html (8,316 bytes)
10. Re: [Amps] 3-500z - intermittent filament (score: 1): Author: "John E. Cleeve" <g3jvc@jcleeve.idps.co.uk>; Date: Thu, 8 Feb 2007 15:40:17 -0000; I would advise caution in resoldering the sleeved pins of the 3-500 et al tubes, for the Eimac spec. and the late Bill Orr, warned that the melting point of the solder used, could be very close to th; /archives//html/Amps/2007-02/msg00132.html (9,894 bytes)
11. Re: [Amps] 3-500z - intermittent filament (score: 1): Author: n4zr@comcast.net; Date: Thu, 08 Feb 2007 16:05:17 +0000; I'm sure John is correct about both the risks of resoldering and the ideal solution, but what to do if you have tubes that have already failed from this cause? Using some of Rich Measures' silver sol; /archives//html/Amps/2007-02/msg00150.html (11,336 bytes)
12. Re: [Amps] 3-500z - intermittent filament (score: 1): Author: Steve Thompson <g8gsq@eltac.co.uk>; Date: Fri, 09 Feb 2007 08:33:08 +0000; Sort of answering my own question from yesterday - the 'silver solder' that Rich supplies is described as Tin-Silver, with 221C melting point. Tin with .5% Copper and 2-4% silver (MP 218-220C) is now; /archives//html/Amps/2007-02/msg00153.html (8,513 bytes)
13. Re: [Amps] 3-500z - intermittent filament (score: 1): Author: "k7rdx" <k7rdx@charter.net>; Date: Fri, 9 Feb 2007 05:44:05 -0800; There is a heat transfer/absorbant compound used in the auto collision industry that may work very well for re-soldering filament pins.We used a mud like substance to absorb heat when welding in sens; /archives//html/Amps/2007-02/msg00156.html (12,421 bytes)
14. Re: [Amps] 3-500z - intermittent filament (score: 1): Author: Peter Chadwick <g3rzp@g3rzp.wanadoo.co.uk>; Date: Fri, 9 Feb 2007 15:19:39 +0100 (CET); There are some higher temperature 'soft solders' around, which don't require the red heat of hard solder. From memory, something called 'comsomal' or similar is about a 300 degree C or so solder. Per; /archives//html/Amps/2007-02/msg00158.html (8,741 bytes)
15. Re: [Amps] 3-500z - intermittent filament (score: 1): Author: "Robert B. Bonner" <rbonner@qro.com>; Date: Fri, 9 Feb 2007 08:28:55 -0600; Guys, I have done this countless times for people without wrecking the tube. Heat the pins with a big soldering iron and gently remove from the tube, clean bare pin and tin. Heat again and clean the; /archives//html/Amps/2007-02/msg00159.html (15,132 bytes)
16. Re: [Amps] 3-500z - intermittent filament (score: 1): Author: "Mike McCarthy, W1NR" <lists@w1nr.net>; Date: Fri, 09 Feb 2007 09:30:46 -0500; Pb90 (90% lead) solder is about 300 C. I have had good luck with "Sb5" alloy which is 95% tin and 5% antimony. It is not the highest of melting points at about 240 C but much higher than 60/40 at 185; /archives//html/Amps/2007-02/msg00160.html (8,765 bytes)

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