Motorola BT100 - Manual (Page 19)

2-8 Overview
BT100 Installation and Operation Manual
not practical to switch to 90 V in a 60 VAC system. There is no damage to the amplifier if the
selector is not changed from the standard 60 V setting. However, changing the selector ensures
that the DC supply does not turn on until the proper input voltage, 38 VAC or 55 VAC, is
reached. This prevents excessive loading of the system power supply during turn-on after a
system shutdown.
The power supply also includes the fast-transfer electronic-crowbar (FTEC/BTA) surge
protector, except for the basic models (BT*-100*H) which include a gas discharge tube. The
FTEC/BTA fires at approximately 245 V and presents a short circuit to the line during periods
of over voltage. After the AC input voltage returns to normal, the FTEC/BTA resumes its open
state. Although the power supply is located under the electronics chassis, you can access the gas
discharge tube or FTEC/BTA through the cover on the top side of the electronics chassis.
Figure 2-8 illustrates the location of the 60/90VAC voltage selector on the power supply circuit
board.
Figure 2-8
BT100 power supply
You must remove the power supply cover to access the selector illustrated in Figure 2-8.
Section 3, “Amplifier Setup” explains changing the setting of this selector to meet system
requirements.