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Re: [TenTec] Care and Feeding of Centurions

To: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Subject: Re: [TenTec] Care and Feeding of Centurions
From: Bry Carling <bcarling@cfl.rr.com>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Sun, 2 Feb 2014 17:15:40 -0500
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>
Ten Tec has some very good detailed instructions on tuning in their manuals. It 
is quite clear.

I apologize for any duplicate messages today. My iPhone was misbehaving again !

Best regards - Bry Carling



> On Feb 2, 2014, at 5:01 PM, "Bob McGraw - K4TAX" <RMcGraw@Blomand.net> wrote:
> 
> I fully agree with Jim on the point that grid current is the most critical 
> value to watch and adhere to in terms of extending tube life.
> 
> For a pair of 3-500's the total grid current should NEVER exceed some 230 to 
> 260 mA MAX!    This is in tune mode with carrier.  Operationally, with SSB 
> the grid current meter would typically display 100 to 130 mA on voice peaks. 
> Plate current in tune with carrier, should be between 700 mA and 800 mA MAX 
> and with SSB, the plate current meter would typically display 300 to 350 mA 
> on voice peaks.  If ones amp while in SSB operation is exceeding these 
> values, likely the tuning is not correct or the amp is being overdriven.  In 
> either case, it is bad for the amp and worst for the stations on either side 
> of your frequency.
> 
> If you wish to operate at less than rated or maximum power, always tune the 
> amp for maximum rated power using the correct values for grid current, plate 
> current and power output.  Then simply reduce the drive to attain the desired 
> operating power.  NEVER retune the amp for the lower power value.
> 
> I'll say this and likely get in a bit of hot water with some folks 
> but..........for those that profess to "dip the plate",  this is correct for 
> a Class C amplifier, but NOT SO for a linear amp in Class AB1 or Class AB2 
> service.  Always tune for maximum output.
> 
> We'll not discuss "tuning to the right side of resonance" as it applies to 
> the tuning a Class C amplifier.  However, you old BC folks will certainly 
> understand this term.
> 
> 73
> Bob, K4TAX
> 
> 
> 
> 
> 
> 
> 
> 
> ----- Original Message ----- From: "Jim Brown" <k9yc@audiosystemsgroup.com>
> To: <tentec@contesting.com>
> Sent: Sunday, February 02, 2014 2:31 PM
> Subject: Re: [TenTec] Care and Feeding of Centurions
> 
> 
>>> On 2/2/2014 12:03 PM, Bob McGraw - K4TAX wrote:
>>> Proper tuning and loading and proper drive is the key to success for long 
>>> amp and tube life.
>> 
>> And also the key to having a cleaner signal. An amp that is over driven 
>> (using AGC to control the drive power) or that is not well tuned will 
>> generate lots of splatter, clicks, and other trash.
>> 
>> I don't know about the 3-500Zs used in the Centurion, but the key to long 
>> life for the ceramic triodes used in the Titan is to keep the grid current 
>> below its limits at all times. My objective is to keep the grid current 
>> below half it's rated value, and my tubes last a LONG time. Grid current is 
>> minimized when the amp is well tuned and not overdriven.
>> 
>> 73, Jim K9YC
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> 
> 
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