[Amps] HELP Modifications for a Kenwood TL922

[Colin Lamb]

"A. A new 3-500Z costs around $150
B. The grids are not grounded in a TL-922.
C. I dont think there is top clearance for a 4-400"

The ham raising the question was not in the US and tubes may be more difficult and expensive there.  The fact that the writer was willing to put in a new filament transformer to run one tube rather than two implied that purchasing a replacement 3-500Z tube was not an option.  I do not know his finances, but I have been in countries where $150 is a years income for some.  

No, the grids are not grounded directly, but pins 2,3 and 4 can be strapped together and will work.

I thought the 4-400 is the same height as the 3-500Z.  I have substituted directly in the SB-220 with no problem.  

Colin  K7FM