[Amps] SB221 Low Output

[Alex Barbon]

Hi to all,

Iam working with an SB221 amp, cantget the power output to go higher than
400watts either AM or SSB voice peak. The tube is confirm good from a
working amp.

Here is my reading

*20m, AM mode ( no modulation )

*Plate current = 680mA
Grid current = 180mA
HV= 2750V SSB
Drive = 90~100watts
Output = 450watts

*40m, AM mode ( No Modulation )
*
Plate current = 580mA
Grid current = 160mA
HV= 2750V SSB
Drive = 90 ~ 100watts
Output = 400watts

Hope to find some info what and where to troubleshootc for this problem.

Thank you,
Alex