You mean some folks actually read the manual? I thought they were just told
the right way to do it by some other non knowing ham that had the info
passed down from generation to generation.
73
Bob, K4TAX
----- Original Message -----
From: "Bry Carling" <bcarling@cfl.rr.com>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Sunday, February 02, 2014 4:15 PM
Subject: Re: [TenTec] Care and Feeding of Centurions
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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