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References: [ +subject:/^(?:^\s*(re|sv|fwd|fw)[\[\]\d]*[:>-]+\s*)*\[Amps\]\s+Failure\s+of\s+a\s+pair\s+of\s+FU728F\s*$/: 23 ]

Total 23 documents matching your query.

1. [Amps] Failure of a pair of FU728F (score: 1): Author: Guido Tedeschi <guidoted@gmail.com>; Date: Sun, 15 Sep 2019 17:59:26 +0200; A friend asked to me why the pair of almost new FU728F tubes on its commercial PA goes south. It seems that, when tubes are warm, there is a short between Grid1 and Cathode on both tubes and, when th; /archives//html/Amps/2019-09/msg00022.html (7,363 bytes)
2. Re: [Amps] Failure of a pair of FU728F (score: 1): Author: Ron Youvan <ka4inm@gmail.com>; Date: Sun, 15 Sep 2019 13:36:28 -0400; A friend asked to me why the pair of almost new FU728F tubes on its commercial PA goes south. It seems that, when tubes are warm, there is a short between Grid1 and Cathode on both tubes and, when th; /archives//html/Amps/2019-09/msg00023.html (8,358 bytes)
3. Re: [Amps] Failure of a pair of FU728F (score: 1): Author: Rick Robinson <w8zt@suddenlink.net>; Date: Sun, 15 Sep 2019 14:55:58 -0400; How about a key up spike in TX power ? A friend asked to me why the pair of almost new FU728F tubes on its commercial PA goes south. It seems that, when tubes are warm, there is a short between Grid1; /archives//html/Amps/2019-09/msg00024.html (9,323 bytes)
4. Re: [Amps] Failure of a pair of FU728F (score: 1): Author: w9oj@indy.rr.com; Date: Sun, 15 Sep 2019 19:24:10 +0000; A friend of mine ruined the finals in his OM4000 by running the amp at low power. Array solutions told him the amp is designed to be run full power or very close to it. 73 de Mike W9OJ and to than 30; /archives//html/Amps/2019-09/msg00025.html (8,469 bytes)
5. Re: [Amps] Failure of a pair of FU728F (score: 1): Author: "Paul Christensen" <w9ac@arrl.net>; Date: Sun, 15 Sep 2019 16:39:04 -0400; power. Array solutions told him the amp is designed to be run full power or very close to it. 73 de Mike W9OJ" I nearly ruined the FU-728F in my OM Power 2000A+ because the cathode was running cold.; /archives//html/Amps/2019-09/msg00026.html (8,774 bytes)
6. Re: [Amps] Failure of a pair of FU728F (score: 1): Author: <w9bs@w9bs.com>; Date: Sun, 15 Sep 2019 16:40:14 -0400; I am the person that Mike is referring to. I was running the OM4000a at 200-300w out (with around 3-4w of drive), and tuning it as normal to the "carrot" on the tuning indicator. I noted that the amp; /archives//html/Amps/2019-09/msg00027.html (10,548 bytes)
7. Re: [Amps] Failure of a pair of FU728F (score: 1): Author: "Joe Subich, W4TV" <lists@subich.com>; Date: Sun, 15 Sep 2019 18:20:50 -0400; On 2019-09-15 4:40 PM, w9bs@w9bs.com wrote: I was running the OM4000a at 200-300w out (with around 3-4w of drive), and tuning it as normal to the "carrot" on the tuning indicator. Sounds like the "ca; /archives//html/Amps/2019-09/msg00028.html (12,625 bytes)
8. Re: [Amps] Failure of a pair of FU728F (score: 1): Author: Guido Tedeschi <guidoted@gmail.com>; Date: Mon, 16 Sep 2019 00:28:23 +0200; Many thanks to everybody for all the answers. The amp is the OM4000A, so the half power is not the 200-300W which could damage the tubes. About the TX spikes, I don't know if the FTDX-5000MP which is; /archives//html/Amps/2019-09/msg00029.html (8,950 bytes)
9. Re: [Amps] Failure of a pair of FU728F (score: 1): Author: Guido Tedeschi <guidoted@gmail.com>; Date: Mon, 16 Sep 2019 00:40:27 +0200; Thanks Joe, but the manual says that the amp protection is activated from Grid current too high... 73 de Guido, ik2bcp Il 16/09/2019 00:20, Joe Subich, W4TV ha scritto: On 2019-09-15 4:40 PM, w9bs; /archives//html/Amps/2019-09/msg00030.html (13,710 bytes)
10. Re: [Amps] Failure of a pair of FU728F (score: 1): Author: "Roger (K8RI)" <k8ri@rogerhalstead.com>; Date: Wed, 18 Sep 2019 04:21:51 -0400; On 9/15/2019 4:39 PM, Paul Christensen wrote: "A friend of mine ruined the finals in his OM4000 by running the amp at low power. Array solutions told him the amp is designed to be run full power or v; /archives//html/Amps/2019-09/msg00033.html (10,649 bytes)
11. Re: [Amps] Failure of a pair of FU728F (score: 1): Author: Greg Wasik <gwasik@gmail.com>; Date: Wed, 18 Sep 2019 14:13:39 -0400; Guessing that if you wanted to run legal limit AM with the OM4000 you would want to avoid any long pauses in your modulation so that the average power is at least 1KW. A dead key would be deadly... G; /archives//html/Amps/2019-09/msg00034.html (11,832 bytes)
12. Re: [Amps] Failure of a pair of FU728F (score: 1): Author: "Joe Subich, W4TV" <lists@subich.com>; Date: Wed, 18 Sep 2019 17:13:41 -0400; "Legal limit" AM is 375 W of carrier -> 1500 W PEP. Whether the OM4000 can be tuned properly for that operating condition is another story. 73, ... Joe, W4TV Greg K1YW _______________________________; /archives//html/Amps/2019-09/msg00035.html (8,709 bytes)
13. Re: [Amps] Failure of a pair of FU728F (score: 1): Author: <dj7ww@t-online.de>; Date: Thu, 19 Sep 2019 01:18:01 +0200; Yes, the pi net design values for 4KW PEP are quite different to 1.5KW. If designed for 4k, circuit Q will be almost doubled for 1.5k. And I doubt it can be tuned on 10m with that high tube impedance; /archives//html/Amps/2019-09/msg00036.html (9,625 bytes)
14. Re: [Amps] Failure of a pair of FU728F (score: 1): Author: "Leigh Turner" <invertech@frontierisp.net.au>; Date: Thu, 19 Sep 2019 14:02:42 +0930; Yeah running a tetrode based muscle amp as a linear for AM is problematic and caution must be exercised in obtaining optimal plate loading and choice of plate load line not causing excessive power to; /archives//html/Amps/2019-09/msg00037.html (12,579 bytes)
15. Re: [Amps] Failure of a pair of FU728F (score: 1): Author: john@kk9a.com; Date: Fri, 20 Sep 2019 07:14:47 -0500; I believe that the tuning of a tetrode is different than a triode - correct? Are they tetrodes less reliable or more finicky? John KK9A I get a kick out of this tube thread. But let me try to add som; /archives//html/Amps/2019-09/msg00040.html (8,506 bytes)
16. Re: [Amps] Failure of a pair of FU728F (score: 1): Author: john@kk9a.com; Date: Fri, 20 Sep 2019 09:35:53 -0500; Guido, ik2bcp did state that the "commercial" amp was a OM4000A driven with 15-20 watts. John KK9A Leigh, It would be too difficult to diagnose why the user had both tubes go out in his commercial am; /archives//html/Amps/2019-09/msg00042.html (8,424 bytes)
17. Re: [Amps] Failure of a pair of FU728F (score: 1): Author: Ron Youvan <ka4inm@gmail.com>; Date: Fri, 20 Sep 2019 10:36:13 -0400; I believe that the tuning of a tetrode is different than a triode - correct? Are they tetrodes less reliable or more finicky? Tetrodes, if operated properly are a rugged as a tetrode, but they are m; /archives//html/Amps/2019-09/msg00043.html (8,728 bytes)
18. Re: [Amps] Failure of a pair of FU728F (score: 1): Author: LB2HG <lb2hg@mimer.no>; Date: Fri, 20 Sep 2019 17:07:54 +0200; _______________________________________________ Amps mailing list Amps@contesting.com http://lists.contesting.com/mailman/listinfo/amps; /archives//html/Amps/2019-09/msg00044.html (7,838 bytes)
19. Re: [Amps] Failure of a pair of FU728F (score: 1): Author: Jim Garland <4cx250b@miamioh.edu>; Date: Fri, 20 Sep 2019 10:05:21 -0600; Two years ago, I completed my first tetrode amplifier (http://www.w8zr.net/160amplifier/160overview.htm), a duo-band (80m/160m) design running three Russian GU74B tetrodes. The experience taught me a; /archives//html/Amps/2019-09/msg00045.html (13,130 bytes)
20. Re: [Amps] Failure of a pair of FU728F (score: 1): Author: "Roger (K8RI)" <k8ri@rogerhalstead.com>; Date: Mon, 23 Sep 2019 04:55:17 -0400; As I have an Emtron manual tune amp I can only comment on the FU728F Tetrode. I would not run a single one of these tubes at 200-330W output, let alone a pair. There are at least 3 versions of the FU; /archives//html/Amps/2019-09/msg00062.html (10,767 bytes)

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