4-18
888-2595-001
12/20/11
WARNING: Disconnect primary power prior to servicing.
Section 4 Theory of Operation
ZX Series
DS13, DS14, DS15, and DS16 via driver transistors Q9, Q12, Q11, and Q10,
respectively.
When appropriate, decimal point scaling is provided by SPDT switches U18 and U19.
Switch U19 activates the third digit decimal point for 1/10 unit reading precision
whenever the reverse power, PA volts, or PA current metering options are selected (e.g.
10.0 A). Switch U18 activates the second digit decimal point for a kilowatts reading (1/
1000 scale) whenever the forward power metering option is selected (e.g. 5.00 kW).
FORWARD POWER position:
The forward power sample from the rms detectors on the I/O filter board is amplified by
variable gain amplifier U24C, the gain of which is set potentiometers R15, R16, R17
and analog switch U8 according to the transmitting mode. This allows for separate
metering calibrations for the FM, FM+HD, or HD/SL transmitting modes. The
calibrated output of U24C is passed to the parallel remote control interface and squaring
multiplier U15. U15 converts the forward power sample from being proportional to
voltage (square root of power) to being directly proportional to power level. This
output is available for metering via meter selector IC U7.
REVERSE POWER position:
The reverse power sample is processed in a manner similar to the forward power
sample described above, except there is a single calibration potentiometer R18
regardless of transmitting mode.
PA VOLTS position:
The PA VOLTS meter reading is simply the PA_VOLTS sample developed by on the PS
interface board from the shared 50V line supplying power to the cooling fans and IPA
module.
PA AMPS position:
The total PA stage current reading appearing in the PA AMPS metering position is
created by a summation of all of the PA1_AMPS through PA8_AMPS sample voltage
brought in from the PA backplanes.
(page 2) Comparators U22A compares the PA1_AMPS sample against a +3V reference
developed by voltage divider R57-R123. Its output will go low and open analog switch
U1A whenever the PA1_AMPS sample exceeds 3V, a condition caused by a +3.5V fault
output from the backplane board assigned to PA1. With switch U1A open, the
PA1_AMPS sample is not allowed to pass through R39 to the PA_AMPS summing
amplifier U28A and U28B.
Summary of Contents for ZX2500
Page 2: ...ii 888 2595 001 12 20 11 WARNING Disconnect primary power prior to servicing...
Page 4: ...iv 888 2595 001 12 20 11 WARNING Disconnect primary power prior to servicing...
Page 6: ...MRH 2 888 2595 001 12 20 11 WARNING Disconnect primary power prior to servicing...
Page 8: ...viii 888 2595 001 12 20 11 WARNING Disconnect primary power prior to servicing...
Page 9: ...12 20 11 888 2595 001 ix WARNING Disconnect primary power prior to servicing...
Page 10: ...x 888 2595 001 12 20 11 WARNING Disconnect primary power prior to servicing...
Page 14: ...xiv 888 2595 001 12 20 11 WARNING Disconnect primary power prior to servicing...
Page 18: ...Table of Contents Continued 4...
