[Amps] Tentec Titan 425

[Jim Brown]

On Sun, 7 Feb 2010 10:03:07 -0800 (PST), Greg Chartrand wrote:

>I just purchased a 425 last week and am waiting for it to arrive. I 
>downloaded the manual;its  an old manual and matches my amp as best I can 
>tell because they has 10m. 
>The manual states that there will be mods to the amp available when the WARC
> bands are available. I can't find any mods for this or anything else on-
>line. I expect they just changed a few values in the input circuit.
>Does anyone have the WARC mods or any other I should consider for this amp?

Greg,

There were several versions of this amp, all "running mods" that made 
relatively minor changes. Adding the WARC bands was one of them. I have three 
of these amps, one without the WARC band mods and two with them. All three 
work on 17M and 12M. The one without the mods doesn't work on 30M. Now, you 
say, why an amp for 30M?  The amps that do work are easy to throttle down to 
200W, and in a pileup, that 3dB can make the difference. 

Tuneup settings for 30M -- set the amp to 40M, Load 3, Tune 0. 

For 17M -- set the amp to 20M, Load 2.4, Tune 0. 

For 12M -- set the amp to 15M, Load 1.7, Tune 0.

In all cases, take these settings as starting points. 

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. 

If you ever need to work on your amp, you'll probably find the schematics on 
my website helpful. These are very nice amps, but they do break sometimes. :) 
Some of the "running mods" are indicated on my schematics. My schematics do 
NOT cover details of the output stage itself, but the Ten Tec manual is 
pretty good on that. 

http://audiosystemsgroup.com/publish.htm  

73,

Jim K9YC