Crescend P10-DE1-C5-001 Series Manual do utilizador - Página 2

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DC power supply voltage is applied to clamps "+/

unit against the polarity reversing.

The power supply voltage comparator (Q1 in the Control Board) open the key Q2, if the power supply voltage is

less than 16.0 V. Open Q2 delivers the supply voltage to the input power comparator U1. Immediately after DC

voltage is applied to the unit, the fan self-test is performed: Q4 opens, opening the fan key Q7 for several

seconds.

When the voltage at the output of the input RF detector, coming to the pin J1-2 of the control board, exceeds 1.4

V, a high voltage at the output of U1 (pin U1/1) appears. Then:

Q5 and Q7 in the Control Board open, switching the cooling fan on;

the control circuits reference voltage, supported by D9 in the Control Board, appears. The right half

of Q3 becomes closed, allowing the reference voltage to go to the circuits;

9.5 VDC sets at the output of control/monitoring circuits voltage regulator (Q9, Q10) in the Control

Board;

the bias voltage for RF amplifying modules U31 and U51 in the Final Stage Board appears. This

voltage comes to the Pre-Amplifier Board, as well;

Q11 and Q21 in the Control Board become open, sending the monitoring signal "TX" and the

voltage to by-pass or T/R switching relays, if this is necessary;

the local voltage regulator (Q5...Q9) is activated in the Pre-Amplifier Board, giving the supply

voltage for the RF amplifying device U1;

with the bias voltage coming, key transistors Q32...Q34 and Q52...Q54 in the Final Stage Board

open, passing the bias voltage to pins 2 of modules U31 and U41, and giving the supply voltages to

comparators of the module current limiters (U32, U52).

Power Control Circuitry Description.

The voltages, proportional to the output forwarded and reversed power, come from pads J4, J6 of the Output

Board via the connector J2 of the Control Board to some inputs of operational amplifiers (OA) set U2 in the

Control Board. These voltages are levered, i.e., they become equal, when the load VSWR reaches the threshold

value (~ 2.5). The threshold is setting by the resistor R12 in the Output Board. OA U2-A and U2-B together

with D6 are selecting the maximum of forwarder and reversed voltages.

The selected voltage comes to the inverting input of OA U3-A. The reference voltage from the potentiometer

RP1 is applied to another input of U3-A. The bias voltage (for modules U31, U51 of the Final Stage Board) is

formed at the emitter of Q16. D7 does not allow this voltage to be greater than 5V. When this voltage reaches its

maximum, Q15 opens, and LED D8 goes on, indicating that the RF output power control loop is open.

The voltage regulator in the Pre-Amplifier Board (Q5...Q8) is also the part of the power control system. This

voltage value is about equal to doubled value of the bias voltage and follow the changes of it.

There are two potentiometers in the Control Board for the power control loop (i.e., the unit output power) setup:

RP1 and RP2. RP2 has the access via the hole in the chassis side wall and is intended for the customer usage.

Usually, this potentiometer is rotated completely CW, when the output power is setting in the factory. Thus, the

customer can only reduce the output power against the set maximum level.

The output power may be reduced automatically with the load VSWR raising (the reversed power detector

signal intercepts the power control). If the unit heatsink temperature reaches +85˚C, the contacts of the thermal

switch close, and the output power fails by ~ 3 dB down.

13.8V". There is the power diode DR, which protects the