Harris Platinum HT EL 2000LS Technical Manual

Harris Platinum HT EL 2000LS Technical Manual Manual pdf 72 page image

indicating normal drive in a PA module. If the sample goes abovethe reference set by R101, U6 pin 1 will go low, indicating anoverdrive fault.* Monitors output reflected power, and protects the module fromelevated load VSWR. Output reflected samples from the outputdirectional coupler assembly are received at J1-22. The VSWRfault threshold is established by R8. If the voltage at U6 pin 5,determined by the reflected power, is greater than the voltage atpin 4, then pin 2 will go low, indicating a VSWR fault.* Monitors the DC power supply voltage, and protects themodule from high and low voltage extremes. The DC supply issampled at J1-23, and is scaled down by R48, R47, and R42. Amaximum voltage reference is established by the +15 Volt regu-lated supply, R43, and R44. If the sample exceeds the reference,U7 pin 1 will go high, indicating an overvoltage fault.Likewise, a minimum voltage reference is established by R45and R46. If the reference exceeds the DC supply sample, U7 pin2 is driven high, indicating an undervoltage fault.* Monitors ISO voltage samples of the quarter modules, protect-ing the amplifier from damage due to imbalances between thetwo halves of a quarter module. The ISO voltage samples arecombined by a OR circuit and collected at J1-3, 4, 16 and 17 onthe controller board.A reference is established by R38 and R81. If the ISO voltagesample exceeds the reference, U6 pin 13 is driven low, indicatinga fault.* Monitors the temperature of the quarter modules, turning offthe amplifier if excessive temperatures are encountered. A volt-age is developed on each module by the thermistor circuitry thatis proportional to the heat sink temperature. These voltages arerouted to the module controller board, J1-5, 6, 7 and 8. Thevoltages are compared to a reference by comparator U13. If anyquarter module temperature voltage is lower than the reference,the comparator output will go low. This switches the output ofthe Schmitt trigger high.*Enables the 50 Volts DC to the quarter modules by controllinga pair of high-power switching FETs (“pass FETs”) located onthe module rear panel. If no faults are present, PAL U1 pin 12sends a signal to U7 pin 8, which controls a circuit that turns onthe pass FETs, a pair of n-channel switching FETs. If a faultcondition occurs, the switching FETs are turned off.The switched 50 Volts dc is reduced to 15 Volts by R39 and U10.This 15 Volts is routed to each quarter module for bias circuitrypower.The incoming 50 Volt DC power is switched on and off by thepass FET assembly, controlling the application of 50 Volts to theQuarter Modules. This switched 50 Volts is reduced to 15 Voltsby regulator U10. The +15 is supplied to each module to be usedfor temperature sensing and FET biasing.The logic will not allow the module to enable if a fault conditionexists, to protect the module from damage.A.2.9 Module Status LEDsEach module uses two front panel LEDs to display its currentoperating status. The LEDs are driven by signals from the PALsand U8 and U9, which are NAND gates configured as buffers.The status can be interpreted from the LEDs as follows:a. Steady Red - 50 Volts applied to the module, but themodule is not enabled. This will normally occur if amodule is removed and then reinserted in the slot.The red LEDs will illuminate then fade out as the supplycapacitors discharge each time the transmitter is turned off.b. 1/2 Green LED Illuminated - Module is enabled but littleor no RF drive is supplied to the module.Driver modules, because of their low input drive level, do nothave a drive level indication. Thus, when a driver module isenabled, both halves of the green LED are illuminated regardlessof drive level. This is the only difference between the PCMsystems on drivers and PAs.a. Full Green LED Illuminated - A full green LED illumi-nated indicates normal module operation. - Module isenabled. Additionally, in PA modules, the presence of RFdrive is indicated.b. No LEDs Illuminated - The 50 Volt DC power is notreaching the module, or the module has been turned off bypulling on the front handle (“mechanical disable”).In some cases this could be the symptom of a module controlfault. If you have not disabled the module turn off the transmittermomentarily while removing the module. This will preventpossible arcing of the input connector pins if the module was infact on but not lighting any LEDs.A.2.9.1 Red LED Fault Blink CodesIf a module fault occurs, the red light will “blink” on and off. Thenumber of blinks between pauses is the “blink code,” and is used todetermine the type of fault. The blink code is as follows:a. 1 Blink - High VSWR condition at the module output.b. 2 Blinks - RF input overdrivenc. 3 Blinks - An elevated ISO voltage resulted from animbalance between halves of a quarter module.d. 4 Blinks - The power supply voltage applied to the moduleis too high or too low.e. 5 Blinks - The quarter module temperature is too high.f. 6 Blinks - The pass FET transistors that switch the 50 Voltsto the quarter modules have failed.A.3 Module TroubleshootingCAUTIONUse extreme care when repairing or testing RF amplifier modules. Be-cause they are capable of producing over 1000 Watts of output power,serious RF burns can result from coming in contact with any high powerpoints inside the module while it is operating.Platinum™ SeriesA-6 888-2457-001WARNING: Disconnect primary power prior to servcing.