2
6
28
amplifier’s operating temperature is correct. Normally the thermostats will present a ground to
J1-5/J1-7 while Control/Monitor transistors A5PC1Q1/Q2 provide open/ENABLE signals to J1-4/
J1-8 due to the high sent on the Exciter’s AMP BIAS CONTROL line (A5PC1J3-3). NAND gates
U1/U2 will supply highs to transistors Q2/Q5, reverse biasing transistors Q3/Q6 which then supply
highs to U1-10/U1-4/U1-5/U2-10. With high ENABLE signals at J1-4/J1-5 and low THERMAL
STATUS signals at J1-5/J1-7, outputs U1-8/U1-6/U2-8 are now low, cutting off control transistors
Q7/Q8/Q9. The opens presented to PS1J3-7/PS2J3-7 by Q7 and Q9 will activate both power
supplies turning on the two 300W Amplifiers (A1/A2) and, therefore, the 500 Watt Power Amplifier
drawer. Concurrently, the open presented by Q6 will keep the respective Control/Metering
AMPLIFIER TEMP indicator inactive via J1-6, J3-4, A5PC1J1-4 or J2-4 and A5PC1Q9 or Q10.
If an overtemperature condition arises on one of the 300W Amplifier assemblies causing the
attendant 175
(
F thermostat to open, a high will occur at either J1-5 or J1-7. Assuming the thermal
problem resides in AMPL 1, pin 11 of gate U1 will now go low, reverse biasing Q2 and forward
biasing Q3. The resulting high at U1-8 will cause Q7 to conduct, providing a ground at J1-3 which
will shut down the 32V Supply (PS1) powering AMPL 1 (A1). To avoid cycling the affected
amplifier back on as it cools, capacitor C3 charges with the appearance of a high at the collector
of Q2 placing a permanent ground latch on the base of Q2 through forward biased Q1. (This
thermal overload latch can only be removed by opening the transmitter’s front panel AC POWER
circuit breaker CB1). At the same time, the low at the collector of Q3 has forced U1-6 high causing
transistor Q8 to place a ground at J1-6. This low TEMP STATUS signal is sent to A3J3-4 and
A5PC1J1-4 turning on the AMPLIFIER TEMPERATURE indicator (A5PC1DS10) using A5PC1Q9.
Also, the low now appearing at A5PC1U1D-12 will produce a low at A5PC1J3-1 which is eventually
seen at the IF/Converter Output AGC Control (PC1J6-10), disabling the AGC circuit so that the
transmitter can operate at a reduced power commensurate with an inactive 300 Watt Power
Amplifier.
2.3f
32V Power Supply:
Vicor PM1-02-520PFC
t
A3PS1, A3PS2
Output
+32V @ 31 Amps
Power Factor
.99 @ 800W
Efficiency
80%
The 32V Power Supply is a single output, high efficiency, 1000 watt switching supply featuring
power factor correction and a volumetrically pleasing package. Each supply is connected directly
to its allocated 300W UHF Power Amplifier assembly and is activated/deactivated through the use
of open/short logic levels provided by the Power Supply/Thermal Interface board. These logic
levels are connected to J3-7, the GSD (General Shut Down) input of each supply.
The 32V Power Supply is not field repairable. If defective, it should be returned to EMCEE for
repair or replacement.