Be careful turning the radio's carrier down too low on that amplifier.
The tubes have no fixed bias on them at all. Sounds backwards, but the radio's carrier serves to control the tubes' plate current. Turn it too low, and the tubes will overheat.
Bad things tend to happen when they do.
If you put a SWR meter and coax jumper between the radio and this amplifier, you will see that the radio is driving into a fairly high SWR when the amplifier is keyed.
When this amplifier was designed, most base radios used tubes. A tube final is more tolerant of high SWR than solid-state finals tend to be.
Installing remedies for the high input SWR, adding fixed bias and making the keying circuit more sensitive is doable, but not simple.
And you won't find a handy "how-to" posted on the net that I have found.
These old amplifers are cool, but incredibly primitive.
Have fun, but watch the tubes to see that they don't "cherry" and overheat.
73