[Hallicrafters] HT-41 mods

[n0alo]

Greetings
Does anyone out there know of any mods that were floating around for the Hallicrafters HT-41 amp?
The one I have here and just now starting to power up and check out has an extra switch with no markings
installed on  the front panel. I haven't pulled the bottom over off yet (darn thing is so heavy) to see where
it is hooked up/wired in.
Many thanks
Lynn
n0alo at kans.com