[TenTec] Titan 425 3CPX800A7 Modification

[Dr. Gerald N. Johnson]

1 KW PEP input was the rule under which the 30S-1 was designed. The 
manual indicates 800 watts input on CW and 900 on SSB allowing 100 watts 
feed through power in the power input computation.

In any PA where you raise the plate voltage and so the RF voltage swing 
and you don't redesign the tank increasing the inductance on EACH band 
and reducing the tuning C you are going to increase the loaded Q because 
it takes the same tuning C to resonate that unchanged coil and more 
voltage means more current in the C and the L. You then raise the load R 
by increasing the loading C, so now you again have raised the ratio of 
the current in the tuning C to the current to the input R and you've 
raised the circulating current again. So for a 20% increase in plate 
voltage, now instead of a circulating current of 1, you have 1.4 amps. 
Or at a typical 2 K plate load Z, and design Q of 12, you had 12 amps, 
now 17.7 amps and the resistive losses in the coil and bandswitch have 
increased by the ratio 17.7 / 12 squared or just over doubled.

On 12/5/2010 9:50 PM, Art Trampler wrote:
> You don't need to modify the Titan to run the 3CPX800A7. Now if you want
> more output, or lower drive with same output, you do need to put more HV on
> the anode and can do that. If you are just looking for a more available,
> often more available tube, they're plug and play replacements. I have a
> Titan and I would not want to push the RF deck to that kind of output. But
> that's just me. Some of the gurus here may have more comments.
>
> As a for instance/why not, I have read (can't verify but have read on
> reflectors) that as big and heavy duty as the Collins 30S-1 appears, it
> really is a 2KW input amp, and some of the components, most notably the
> bandswitch, are not made to hold up to the voltage or current of much higher
> operation.
>
> 73,
> Art, K0RO
>
>
73, Jerry, K0CQ