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41. [AMPS] AL1500 (score: 1): Author: 2@vc.net (2); Date: Wed, 5 Dec 2001 07:54:16 -0800; just for a // During the Grate Parasitics Debate, our "recognized expert" clearly succeded in proving that "There is no safety in technological hubris" and that his opponent would not make an under-; /archives//html/Amps/2001-12/msg00111.html (9,881 bytes)
42. [AMPS] AL1500 (score: 1): Author: 2@vc.net (2); Date: Wed, 5 Dec 2001 07:54:22 -0800; // Out of the last five 8877s I autopsied, only one indicated parasite damage (loose gold) -- which came from an out-of-warranty AL-1500 amplifier. // One of the two tubes in my SB-220 was manufactu; /archives//html/Amps/2001-12/msg00113.html (10,554 bytes)
43. [AMPS] AL1500 (score: 1): Author: 2@vc.net (2); Date: Wed, 5 Dec 2001 08:02:27 -0800; // Some Alphas apparently C-E-short their interrupt transistor. // If grid-overcurrent protection circuits worked I would not be seeing kaput 8877s with loose gold about. - R. L. Measures, 805.386.3; /archives//html/Amps/2001-12/msg00115.html (9,431 bytes)
44. [AMPS] AL1500 (score: 1): Author: oz1pif@get2net.dk (Peter Frenning, OZ1PIF); Date: Wed, 5 Dec 2001 16:29:26 +0100; -- Original Message -- From: "Tom Rauch" <w8ji@akorn.net> To: "alex" <alex@sandlabs.com>; <kc5vdj@yahoo.com>; "Peter Chadwick" <Peter.Chadwick@zarlink.com> Cc: "amps" <amps@contesting.com> Sent: Wedn; /archives//html/Amps/2001-12/msg00116.html (9,596 bytes)
45. [AMPS] AL1500 (score: 1): Author: paulc@mediaone.net (Paul Christensen); Date: Wed, 5 Dec 2001 14:04:41 -0500; If I am not mistaken, the original Alpha 77 (model PA-77) uses such a grid-protection circuit. However, I don't recall how well the switching transistor is buffered and isolated from the grid. If I; /archives//html/Amps/2001-12/msg00118.html (9,277 bytes)
46. [AMPS] AL1500 (score: 1): Author: paulc@mediaone.net (Paul Christensen); Date: Wed, 5 Dec 2001 16:15:19 -0500; // Some Alphas apparently C-E-short their interrupt transistor. If I am not mistaken, the original Alpha 77 (model PA-77) uses such a grid-protection circuit. However, I don't recall how well the swi; /archives//html/Amps/2001-12/msg00121.html (7,143 bytes)
47. [AMPS] AL1500 (score: 1): Author: 2@vc.net (2); Date: Wed, 5 Dec 2001 13:29:56 -0800; // Fast enough is no observable damage to the electron tube with a high-pot tester, Over-current fuses open to limit current, but over-current transistors often short, which does not limit current.; /archives//html/Amps/2001-12/msg00123.html (9,886 bytes)
48. [AMPS] AL1500 (score: 1): Author: stevek@jmr.com (Steve Katz); Date: Wed, 5 Dec 2001 13:45:23 -0800; [Steve Katz] Murphy also said that a dropped 8877 will land on your little toe and break it. -- FAQ on WWW: http://www.contesting.com/FAQ/amps Submissions: amps@contesting.com Administrative request; /archives//html/Amps/2001-12/msg00124.html (8,954 bytes)
49. [AMPS] AL1500 (score: 1): Author: Ian White, G3SEK" <g3sek@ifwtech.com (Ian White, G3SEK); Date: Wed, 5 Dec 2001 22:34:24 +0000; That's not very specific... and what exactly do you mean by an "interrupt transistor"? So you do have difficulty in naming even one specific circuit, then? -- 73 from Ian G3SEK Editor, 'The VHF/UHF D; /archives//html/Amps/2001-12/msg00125.html (10,107 bytes)
50. [AMPS] AL1500 (score: 1): Author: kc5vdj@yahoo.com (Jim Bryant); Date: Wed, 05 Dec 2001 19:02:03 -0600; How much of this gold sputtering could be caused by long-term long-duration mild-to-moderate overdrive of the grid? I ask this, because I know plenty of moron hams with amps that obviously do not und; /archives//html/Amps/2001-12/msg00130.html (10,029 bytes)
51. [AMPS] AL1500 (score: 1): Author: paulc@mediaone.net (Paul Christensen); Date: Wed, 5 Dec 2001 20:40:50 -0500; Regarding the Alpha PA-77... I just reviewed the schematic and here is my understanding of the transistorized grid over-current circuit: The cathode-side of a 8.2 V zener is coupled to the 8877's cat; /archives//html/Amps/2001-12/msg00131.html (11,116 bytes)
52. [AMPS] AL1500 (score: 1): Author: paulc@mediaone.net (Paul Christensen); Date: Wed, 5 Dec 2001 20:45:46 -0500; Clarification.... "The anode side of the zener is then brought to THE COLLECTOR OF a discrete darlington transistor pair (Q4 & Q5)." -Paul, W9AC -- FAQ on WWW: http://www.contesting.com/FAQ/amps Subm; /archives//html/Amps/2001-12/msg00132.html (8,399 bytes)
53. [AMPS] AL1500 (score: 1): Author: 2@vc.net (2); Date: Wed, 5 Dec 2001 18:11:50 -0800; \ The active device whose job is to interrupt the flow of grid current. The amplifier that the gold-sputtered 8877 in Figure 24 on my Web site was removed from a AL-1500, which has a grid "protectio; /archives//html/Amps/2001-12/msg00133.html (10,100 bytes)
54. [AMPS] AL1500 (score: 1): Author: 2@vc.net (2); Date: Wed, 5 Dec 2001 18:11:52 -0800; \ Overdrive normally flakes off the cathode's emissive coating. There's a photograph of a flaked cathode in "Parasitics Revisited" in the September/October 1990 issue of *QST*. As can be seen in the; /archives//html/Amps/2001-12/msg00134.html (10,409 bytes)
55. [AMPS] AL1500 (score: 1): Author: jstrohm@texas.net (Jim Strohm); Date: Wed, 5 Dec 2001 21:05:26 -0600; AG6K said ... Uhh ... without putting words in Tom's mouth ... because it was easier to blame Eimac's bum run of tubes for most of the late 1980s than to blame amplifier engineering shortcomings? Jim; /archives//html/Amps/2001-12/msg00135.html (8,715 bytes)
56. [AMPS] AL1500 (score: 1): Author: 2@vc.net (2); Date: Wed, 5 Dec 2001 20:15:53 -0800; \ Perhaps grid-current does not stop soon enough? The 77 has a history of gold-sputtering 8877s. Beats me. tnx, Paul - R. L. Measures, 805.386.3734,AG6K, www.vcnet.com/measures. end -- FAQ on WWW: h; /archives//html/Amps/2001-12/msg00136.html (11,024 bytes)
57. [AMPS] AL1500 (score: 1): Author: 2@vc.net (2); Date: Wed, 5 Dec 2001 20:35:56 -0800; Agreed, however, this was way after the heat dam mfg defect was corrected, and most amp builders knew it. As I see it, most of us knew that Henry, Alpha, Dentron and all the rest used parasitic supp; /archives//html/Amps/2001-12/msg00137.html (9,065 bytes)
58. [AMPS] AL1500 (score: 1): Author: Peter.Chadwick@zarlink.com (Peter Chadwick); Date: Thu, 6 Dec 2001 07:58:01 -0000; So you can with good tubes. There are many evidences of tubes such as klystrons in TV and radar service which have still met full spec after 120,000 operating hours. My 6L6 regulator tube still meets; /archives//html/Amps/2001-12/msg00139.html (11,845 bytes)
59. [AMPS] AL1500 (score: 1): Author: Ian White, G3SEK" <g3sek@ifwtech.com (Ian White, G3SEK); Date: Thu, 6 Dec 2001 12:47:50 +0000; Thanks for providing some concrete information, Paul. So the way it's normally meant to operate is that grid current flows down through R3, and when the voltage drop exceeds about 0.6V it turns on Q2; /archives//html/Amps/2001-12/msg00141.html (12,154 bytes)
60. [AMPS] AL1500 (score: 1): Author: Ian White, G3SEK" <g3sek@ifwtech.com (Ian White, G3SEK); Date: Thu, 6 Dec 2001 13:18:07 +0000; [...] Sorry - "R3" should be R20, everywhere. -- 73 from Ian G3SEK Editor, 'The VHF/UHF DX Book' 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.com/g3sek -- FAQ on WWW: http://www.conte; /archives//html/Amps/2001-12/msg00142.html (9,754 bytes)

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