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1. [Amps] SB221 Low Power Help (score: 1): Author: Rahul Sathe <vu3raz@gmail.com>; Date: Tue, 8 Sep 2009 21:02:31 +0530; Hello Experts, My name is Rahul call VU3RAZ. This is my first post to the list. I am seeking help on fixing my old SB221. as such the amp works on all bands, no arc or parastatics, tuning and loading; /archives//html/Amps/2009-09/msg00092.html (7,008 bytes)
2. Re: [Amps] SB221 Low Power Help (score: 1): Author: Rahul Sathe <vu3raz@gmail.com>; Date: Tue, 8 Sep 2009 22:28:23 +0530; I will try that tomorrow don. For the input circuit does nothing on 14 MHz VSWR is nowhere near 2. I am thinking of ripping the input tuned circuit and replacing it with a simple parallel resonant ck; /archives//html/Amps/2009-09/msg00096.html (10,018 bytes)
3. Re: [Amps] SB221 Low Power Help (score: 1): Author: Rahul Sathe <vu3raz@gmail.com>; Date: Tue, 8 Sep 2009 22:59:00 +0530; Yes I tried that Gerald, the internal tuner eases the SWR and improve drive, still no luck beyond ~ 400 mA with 2 tubes on 20. _______________________________________________ Amps mailing list Amps@c; /archives//html/Amps/2009-09/msg00099.html (11,301 bytes)
4. Re: [Amps] SB221 Low Power Help (score: 1): Author: Rahul Sathe <vu3raz@gmail.com>; Date: Tue, 8 Sep 2009 23:09:15 +0530; Carl, Plate Idle Current in SSB position is ~ 120 to 125 mA. I have to check the grid chokes as suggested by you, how abt grounding the grids directly without chokes? Checked the tubes... there is no; /archives//html/Amps/2009-09/msg00100.html (11,114 bytes)
5. Re: [Amps] SB221 Low Power Help (score: 1): Author: Rahul Sathe <vu3raz@gmail.com>; Date: Wed, 9 Sep 2009 22:28:49 +0530; Thanks for the post Jay, VSWR "high" is above 2... particularly on 20 and 15. the same can not be tuned with the stock input coils. On other bands it is well matched... mostly below 1.2. If I ignore; /archives//html/Amps/2009-09/msg00124.html (11,177 bytes)
6. Re: [Amps] SB221 Low Power Help (score: 1): Author: Rahul Sathe <vu3raz@gmail.com>; Date: Thu, 10 Sep 2009 22:42:36 +0530; Great ! Just replaced a flaked input cap... VSWR still off the scale on 20, still with 100 W CW the loading has improved to 500mA @ 2500V 400 mA with RTTY 2 tone. I guess that will be the top limit o; /archives//html/Amps/2009-09/msg00174.html (25,234 bytes)
7. Re: [Amps] SB221 Low Power Help (score: 1): Author: Rahul Sathe <vu3raz@gmail.com>; Date: Fri, 11 Sep 2009 20:51:22 +0530; Great info carl. I think I will also rebuild the input tuned ckt with new caps. The idle current is about 90 in CW and ~125 in SSB. The HT pulls about 300V on full CW drive. I guess I have to work on; /archives//html/Amps/2009-09/msg00175.html (30,795 bytes)
8. [Amps] 4-400 Amp Help (score: 1): Author: Rahul Sathe <vu3raz@gmail.com>; Date: Thu, 31 Mar 2011 23:27:48 +0530; Hello Experts, I just finished building a QB4-1100 / 4-400 Grid Driven amp. with following configuration.. 1 X QB4-1100 450 V DC Screen -150 VDC on CGird, switched / keyed to ~ -50V DC for idle curre; /archives//html/Amps/2011-03/msg00303.html (6,951 bytes)

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