[Johnson] Invader 2000 Grid Current

[David C. Hallam]

Well, I guess I am going to have to take the transmitter off my desk and 
open it up.  Now I have no output.  The driver portion is still 
working.  Plate voltage is 2400V no load and 2100V under load.  The 
4-400A's have unknown usage.  They were in the rig when I bought it.  
Maybe its something in the loading section as the controls are very 
stiff to turn.  Are there any known problems with the loading capacitors?

If it's tubes, I have a used pair of PL-172's, a new pair of 4-400A's, 
and 2 or 3 used 4-400A's.

David
KW4DH

On 3/17/2014 7:44 PM, WQ9E at btsnetworks.net wrote:
> The big problem with the Tbolt is the low (2,000 volt) plate voltage which forces the 4-400A final into AB2 to reach the 2KW PEP rating.  My Heathkit KL-1 (same basic 4-400A circuit) but with 3,000 volts under load runs class AB-1 to its 2KW rating and even my little Yaesu FT-817 will push it to almost 2KW PEP.  Johnson also used the same relatively low voltage for the Invader 2000 and it has the same issue as the Tbolt when driven to the old 2KW rating.  The Invader 2000 looks pretty ugly on a spectrum analyzer when approaching the rated 2KW input.
>
> Depending upon the life left in the Tbolt tubes I would treat it as a 1,200 to 1,500 watt PEP input rig which it will do without driving in into the grid current region.  The amp will run cooler and is much cleaner and the signal strength difference is almost unnoticeable.
>
> I drive my Tbolt with a Pacemaker and the combination is pretty clean but it doesn't run quite at the old 2KW legal limit with the available drive from the Pacemaker.
>
> Rodger WQ9E
>
>
>
>

-- 
"I predict future happiness for Americans if they can prevent the government from wasting the labors of the people under the pretense of taking care of them."
Thomas Jefferson


---
This email is free from viruses and malware because avast! Antivirus protection is active.
http://www.avast.com