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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