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1. [Amps] SB-220 Bias Question (score: 1): Author: RICHARD SOLOMON <w1ksz@q.com>; Date: Thu, 11 Jun 2009 03:02:55 +0000; The stock SB-220 comes with a 5.1 volt (+/-) bias. A new Meter Board I have provides 6.8 volt bias. Any thoughts on what the increase in voltage will do to the linearity ? Has anyone measured the Gri; /archives//html/Amps/2009-06/msg00048.html (6,493 bytes)
2. Re: [Amps] SB-220 Bias Question (score: 1): Author: Vic K2VCO <vic@rakefet.com>; Date: Wed, 10 Jun 2009 21:00:11 -0700; If the zero-signal plate current is close to what the book says it should be (I've forgotten exactly but someone will know) then it will be OK. -- 73, Vic, K2VCO Fresno CA http://www.qsl.net/k2vco __; /archives//html/Amps/2009-06/msg00049.html (6,897 bytes)
3. [Amps] SB-220 bias question (score: 1): Author: Gudguyham@aol.com; Date: Sat, 29 Aug 2009 07:09:07 EDT; It was always my understanding with the SB-220 and other older amps that the reason for lowering the plate voltage on the 3-500's or whatever tube, was to comply with FCC regulations. Years ago the r; /archives//html/Amps/2009-08/msg00593.html (7,870 bytes)
4. Re: [Amps] SB-220 bias question (score: 1): Author: Gudguyham@aol.com; Date: Sat, 29 Aug 2009 07:14:43 EDT; to short out 4 of the diodes on CW to lower the idle current and have normal SSB idle CORRECTION: Should have been short out 4 diodes on SSB....sorry _______________________________________________ A; /archives//html/Amps/2009-08/msg00594.html (6,501 bytes)
5. Re: [Amps] SB-220 bias question (score: 1): Author: "Carl" <km1h@jeremy.mv.com>; Date: Sat, 29 Aug 2009 09:00:46 -0400; Many operate the SB-220 on RTTY and digi modes where the CW position is a key to transformer survivability. The same for 12/17M where the tank circuits are far from optimum and bandswitch arcing can; /archives//html/Amps/2009-08/msg00595.html (9,059 bytes)
6. Re: [Amps] SB-220 bias question (score: 1): Author: gudguyham@aol.com; Date: Sat, 29 Aug 2009 10:35:07 -0400; So in other words it's not a technical issue so much as it is a "idiot proof" fail safe measure? Many operate the SB-220 on RTTY and digi modes where the CW position is a key to transformer survivabi; /archives//html/Amps/2009-08/msg00597.html (10,384 bytes)
7. Re: [Amps] SB-220 bias question (score: 1): Author: "Carl" <km1h@jeremy.mv.com>; Date: Sat, 29 Aug 2009 10:50:36 -0400; Thats one way of putting it Lou. Carl KM1H So in other words it's not a technical issue so much as it is a "idiot proof" fail safe measure? Many operate the SB-220 on RTTY and digi modes where the CW; /archives//html/Amps/2009-08/msg00598.html (10,397 bytes)
8. Re: [Amps] SB-220 bias question (score: 1): Author: "Joe Subich, W4TV" <lists@subich.com>; Date: Sat, 29 Aug 2009 11:33:35 -0400; No. The SB-220 will not survive RTTY operation in "full smoke" mode. 100% duty cycle at 1500 W output will cook both the transformer and the output. Running at lower power keeps the transformer and; /archives//html/Amps/2009-08/msg00600.html (12,692 bytes)
9. Re: [Amps] SB-220 bias question (score: 1): Author: gudguyham@aol.com; Date: Sat, 29 Aug 2009 12:10:15 -0400; The SB-220 will not survive RTTY operation in "full smoke" @@@@@ Agreed, for sure, but the AAL-80, AL-82 et al. do not change the plate voltage on any mode.? The operator is told to adjust power outp; /archives//html/Amps/2009-08/msg00602.html (13,484 bytes)
10. Re: [Amps] SB-220 bias question (score: 1): Author: "DF3KV" <df3kv@t-online.de>; Date: Sat, 29 Aug 2009 18:56:58 +0200; To do so you have to modify the pi-net, as the output impedance of the tube will be much higher 73 Peter My whole point is to run the tubes at higher plate voltage with less plarte and grid current f; /archives//html/Amps/2009-08/msg00603.html (8,188 bytes)
11. Re: [Amps] SB-220 bias question (score: 1): Author: gudguyham@aol.com; Date: Sat, 29 Aug 2009 13:17:26 -0400; NO WAY To do so you have to modify the pi-net, as the output impedance of the tube will be much higher 73 Peter To do so you have to modify the pi-net, as the output impedance of the tube will be muc; /archives//html/Amps/2009-08/msg00604.html (8,792 bytes)
12. Re: [Amps] SB-220 bias question (score: 1): Author: "Bill, W6WRT" <dezrat1242@yahoo.com>; Date: Sat, 29 Aug 2009 11:01:38 -0700; ORIGINAL MESSAGE: REPLY: The real key to transformer survivability when running RTTY is the amount of DC plate current drawn. The transformer does not care which position the bias switch is in. If yo; /archives//html/Amps/2009-08/msg00606.html (9,066 bytes)
13. Re: [Amps] SB-220 bias question (score: 1): Author: "Joe Subich, W4TV" <lists@subich.com>; Date: Sat, 29 Aug 2009 18:02:32 -0400; No, I didn't miss the point. Running an amplifier in a mis-tuned condition (tune for 1500 W Output and drive to 800 W Out) is hazardous and inefficient. If you tune the amplifier for 800 W at the hi; /archives//html/Amps/2009-08/msg00611.html (16,600 bytes)
14. Re: [Amps] SB-220 bias question (score: 1): Author: "Joe Subich, W4TV" <lists@subich.com>; Date: Sat, 29 Aug 2009 18:02:32 -0400; Absolutely "way" ... if you run the higher late voltage with lower current and only 700 - 800 watts out in RTTY, the plate load impedance of the tubes will be two to three times higher that the desi; /archives//html/Amps/2009-08/msg00612.html (11,211 bytes)
15. Re: [Amps] SB-220 bias question (score: 1): Author: Roger <sub1@rogerhalstead.com>; Date: Sat, 29 Aug 2009 18:56:14 -0400; Rephrasing: An amp should be tuned up AT the power level it's going to run, OR a "tune" switch that gives less plate voltage but the amp is tuned up at the same ratio of plate current to plate voltag; /archives//html/Amps/2009-08/msg00613.html (18,637 bytes)
16. Re: [Amps] SB-220 bias question (score: 1): Author: "DF3KV" <df3kv@t-online.de>; Date: Sun, 30 Aug 2009 01:21:26 +0200; And the first thing to blow up will be the band switch 73 Peter Absolutely "way" ... if you run the higher late voltage with lower current and only 700 - 800 watts out in RTTY, the plate load impedan; /archives//html/Amps/2009-08/msg00614.html (11,663 bytes)
17. Re: [Amps] SB-220 bias question (score: 1): Author: "Carl" <km1h@jeremy.mv.com>; Date: Sat, 29 Aug 2009 19:23:49 -0400; The SB-220 is a compromise anyway as the Ep and Ip dont go to half on CW and drive has to be dropped for 1000W Input to maintain the same load impedance. With 100W drive the typical key down output o; /archives//html/Amps/2009-08/msg00615.html (12,495 bytes)
18. Re: [Amps] SB-220 bias question (score: 1): Author: Gudguyham@aol.com; Date: Sat, 29 Aug 2009 20:30:52 EDT; No, I didn't miss the point. Running an amplifier in Show me where I said that _______________________________________________ Amps mailing list Amps@contesting.com http://lists.contesting.com/mailma; /archives//html/Amps/2009-08/msg00616.html (8,291 bytes)
19. Re: [Amps] SB-220 bias question (score: 1): Author: "Bill, W6WRT" <dezrat1242@yahoo.com>; Date: Sat, 29 Aug 2009 17:33:12 -0700; ORIGINAL MESSAGE: REPLY: Inefficient, yes, but how could that possibly be hazardous? Bill W6WRT _______________________________________________ Amps mailing list Amps@contesting.com http://lists.cont; /archives//html/Amps/2009-08/msg00617.html (9,181 bytes)
20. Re: [Amps] SB-220 bias question (score: 1): Author: "Joe Subich, W4TV" <lists@subich.com>; Date: Sat, 29 Aug 2009 20:48:51 -0400; Reducing the power output without changing the plate voltage will result in a miss-tuned condition. If the pi-network is tuned for full output and the drive reduced (power adjusted). If the output i; /archives//html/Amps/2009-08/msg00618.html (9,666 bytes)

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