Acom 2000A Operating Manual page 18

A 2.5 minutes tube warm-up period follows during which heater and bias voltages are applied.
During warm-up the amplifier remains in STB, so you can operate with the transceiver only.
You can also change the antennas manually or read the HELP texts during the warm-up period.
When you intend to have a brief pause in operating (e.g. less than 30 minutes),
it is better to leave the amplifier in STB mode instead of turning it off. Tube life
may be shortened by repeatedly turning on and off the tube heater supply. If
you are concerned about this, discuss it with your dealer.
However, if you unintentionally power-off the amplifier, it is best to switch it
on again immediately. When the pause is short (up to one minute) and the
cathodes are still warm, the warm-up period is shortened significantly, which
reduces the waiting time and prolongs the tube's expected life.
b) MAIN MENU
After the indicated warming up period expires, all voltages are automatically applied to the tubes
in the correct sequence. At the same time the stepper motors conduct a self-test and finally
tune the plate circuit to the frequency segment on which the amplifier was last used. You hear
"R" being sent in CW and the MAIN MENU appears on the TFT display (see figure 4-2 below)
16
Fig.4-1 RCU display during warmup
N O T E
N O T E