4-1000 screen voltage

[kc2ifr]

My transmitter is a 4-1000 modulated by a pair of 833's. My question is this.....I am running the screen on the 4x1 at 400 volts. The included spec sheet calls for 500 volts. To modulate the screen I have a 15 henry choke in series with the screen. The plate voltage on the 4x1 and the 833's is 3400 volts. I can vary the screen voltage up to about 600 volts but the 4x1 seems to like 400 volts. At that voltage the screen draws about 125 mills. Is the screen voltage I am running going to be a problem. The transmitter output is 1000 watts of carrier and the IF I modulate it fully, the pep output is about 4500 watts but of course I would not do that!
So  am I running the 4x1 at its best.
BTW....the toob shows very little color at this power level.

Bill

[kc2ifr]

Maybe my question about the 4x1 was not clear.
How important is the screen voltage on plate modulated 4-1000.

Bill

[kc2ifr]

I only have 1 4x1 in the rf deck........but I have 2 833's in push shove in the modulator.......

[kc2ifr]

Ok understood.......
Here is a pic of the meters with the rig running 1000 watts output.
The 2 empty meter holes were going to hold the cathode meters for the 2 833's but I left them on the modulator deck.
The meter not labeled is the 4x1 cathode current.

Bill

[kc2ifr]

OK Brian,
Im not running the grid drive that hi for more power.......its just that I thought the toob ran better at that drive level. I will be going on the air soon and will drop the drive down to about 30 to 35 mills as recommended by Eimac.
 
I think Ill lower the drive untill the power starts to drop off and then increase it untill I dont see any gain in output.

Stay tuned.......
Bill

[W2VW]

As you probably suspect, look at peak power when reducing the grid drive.

FWIW I used to run mine @ 38 mills Ig.

[KA1ZGC]

Yep, do it under max modulation and you should be fine.

Kinda curious how much grid bias you're running. That will figure into that minumum drive requirement somewhat.

[Opcom]

KC2 - I have the same problem, very similar operating parameters. The 4-1000 does not work efficiently at low voltages but I have run it at 2300V in tests.