Model 150A400
Manual Text
3-2
REV B
The output of Q1A and Q1B are coupled through matching transformers T3 and T4 to the output connector P1.
Over current protection is provided by U1, U3, U4 and U5, by sensing the input current and lowering the bias
voltage if the current goes above the normal operating level.
3.5
TWO WAY COMBINER
The outputs of the two Basic Power Modules are fed to the two way combiner where the power is summed and then fed to the
main output of the amplifier.
3.6
POWER SUPPLY
Refer to
"Schematic Diagram Number 1010877, Power Supply"
.
Input AC power is fed through RFI Filter FL1 before being switched by the circuit breaker CB1. The AC input
power is fed from CB1 to the four switching power supplies, PS1, PS2, PS3, PS4.
The four switching supplies work on line voltages of 90 to 132 VAC and 180 to 264 VAC 50/60 Hz. The input
voltage is selected automatically to conform to the supplied line voltage. No manual changes are required when
switching from one supply voltage to another.
The outputs of PS1 and PS2 are connected in series to supply 33 VDC to the Basic Power Modules (A & B)
amplifier circuits. The output of PS3 supplies
±
12VDC and +5VDC to the operate/control circuits and the gain
control circuit. The fourth supply (PS4) supplies 28VDC to the driver amplifier. All the have current limited
outputs to protect them from shorts or over dissipation.
The 33VDC is fed through L1, which keeps switching transients from the supplies out of the amplifier circuits, to
the amplifier circuits.
If the currents in the output amplifiers get too high for the on board circuits to control, or if the heat sink
temperature gets too high, a fault signal is generated to shut down PS1 and PS2, and PS4.
3.7 A4 OPERATE/CONTROL BOARD (SCHEMATIC DIAGRAM No. 1008597)
The A4 Operate/Control Board is a microcontroller-based printed wiring board (PWB) assembly that allows
sensing and control of internal signals as well as remote personal computer (PC) control via on-board RS-232 and
IEEE-488 data communications ports. The A4 Operate/Control Board utilizes a state-of-the-art, Reduced
Instruction Set Computing (RISC) microcontroller that can quickly and reliably perform all front panel control and
monitoring tasks, thereby allowing real-time control to the Model 150A400 via either remote bus. Besides being
reported remotely, all amplifier faults are continuously monitored and indicated via the unit’s front panel VFD.
3.8
A3 GAIN CONTROL (SCHEMATIC DIAGRAM NO 1009914)
The gain control allows for gain adjustment either from the front panel or from the RS-232 Port or the IEEE-488
Port. U4 and U5 are 2 electronic attenuators connected in series to give a minimum adjustment range of 18 dB.
U1 is a switch that selects front panel control or remote control.
