From: "Jim Brown" <jim@audiosystemsgroup.com>
Subject: Re: [Amps] Tentec Titan 425
These amps drive to full power with about 50 watts. Do NOT depend on ALC to
set the power. Instead, back off on the drive power using the output power
setting on your transceiver to get the desired power output from the amp. I
start with about 30 watts of drive and tune the amp (Load and Tune) for
maximum output on an SWR meter external to the amp. I keep the switchable
meter ALWAYS set to watch grid current (see next paragraph). Tuning for max
output will minimize harmonics and clicks.
Operationally, the most important thing to watch on this amp is grid current.
Too much grid current will cause early failure of the tubes. Keeping the grid
current down will make them run forever. The ABSOLUTE max grid current is
60mA per tube (120mA, full scale on the grid current meter). I run the grid
current low -- my goal is to keep it below 30mA. Why so low? Because when
something goes wrong in the antenna system, grid current will soar (because
the amp has no protection to kill power when grid current rises).
Protecting against excessive grid current when something breaks is the only
good reason for ALC. I've never used it.
### Then why not just add a simple grid over current circuit ??
It's just a sense resistor, transistor, and relay...and pot.
Then you can protect the 4 watt floozy grids in those expensive tubes.
### IMO, not installing electronic grid over current, on tubes using
delicate grids is just asking for trbl. The fix is so easy. What were
they thinking? They saved all of < $10.00 The concept has been around
for > 30 years. My buddy has a Ten Tec centurion. [ 2x3-500Z]. When he
1st got it, it sucked full bore ZSAC... on RX! Ten Tec later issued a..'fix'
Do those folks know how to engineer anything correctly ? Care and feeding sez
you require grid over current protection.. [ and also plate over current]...so
why didn't they ?
## The centurion manual goes on ad nauseum about the 3.5 kva CCS xfmr ten tec
uses... then also states it's 7 kva IVS ! That IVS rating is a throw
back to the
Orr books. "Int voice service" The centurion will do 1.3 kw pep on ssb.. and
that's it. So much the 3.5 kva CCS nonsense.
Later... Jim VE7RF
73,
Jim K9YC
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