[Amps] Drake L4B to 6 Meters Help

[Michelle]

Ok, Here's where I am at:  Removed zener from the self cut off bias mod, 
Idle current now 200 ma.

Plate voltage 2300 under load (SSB mode)
Plate current  .810  (was 650)
Grid  230 (was 220)
Drive  100 watts
Output  750 watts (key down, not pep)

No change in output with the raised idle current

Replaced tubes with known good ones (No change)

Checked Bird 43 with 1000 wt slug against another 43 with a 500 wt slug and 
2  Drake W-4 wattmeter's, setting the amp to 500 watts
with the 43 with 500 watt slug, both  W-4's read 500 watts, but the 43 with 
1000 watt slug read 375, put the slug in the other 43 same
thing, looks like I have a bad slug that's a bit more than 5%. At full 
output the W-4 reads 850 watts.

Michelle
WB8QGR