Shure pg4 wireless receiver service manual
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Extracted text from shure pg4 wireless receiver service manual (Ocr-read)
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2 25A1104 (Rev.1) DETAILED DESCRIPTION Front Panel 1audio LED Indicates strength of incoming audio signal: green for normal, amber for strong, red for peak. 2ready LED Green light indicates system is ready for use. 3 LED screen 4channel button Back Panel 1 AC adapter jack 2 Adapter cord tie-off 3 XLR balanced microphone output jack 4 1/4 unbalanced output jack 1 2 3 4 3 4 2 1
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3 25A1104 (Rev.1) CIRCUIT DESCRIPTION General block diagram description. The receiver consists of the following components: Image filters, predictive diversity circuitry, down-converter, first IF strip, SAW filter, second mixer, second IF strip, ceramic filter, detector, RSSI buffer, low pass filter, RMS detector and expander, mute circuit, balanced and unbalanced audio outputs, tonekey detection circuit, noise squelch circuit, microprocessor and several voltage regulators. The PG4 receiver has two internal antennas mounted to the circuit board via antenna connectors.. RF Strip The receiver incorporates Shure's patented Predictive Diversity scheme. The microprocessor's A/D input is continuously monitoring buff- ered RSSI output from the TP_RSSI_A2D test point. It uses a dynamically adaptive threshold to control dual PIN diode D510, to switch between the internal antennas. The received RF signal enters an image rejection helical filter (FL510). The filter FL510 in conjunction with a discrete filter post LNA attenuates the 1st LO frequency from reaching the antenna ports. The RF signal is then down-converted with IC520, an integrated receiver front-end chip that includes: LNA (low noise amplifier), a GaAs FET mixer, and an IF buffer stage. The 50- Ohm impedance of the mixer output's buffer stage is matched to the SAW filter FL600. The signal enters the 1st first IF amplifier, which consists of Q603, and then it is filtered via a secondary LC filter comprised of C533, L523, C607, and C608. The second mixer is part of IC610, which also contains the 2nd IF amplifier, limiter, FM detector, and wide dynamic range RSSI circuitry. The second mixer down-con- verts the first IF signal (110.6 MHz) down to the second IF frequency of 10.7 MHz. The second IF signal is filtered with 10.7MHz ceramic filters FL620 and FL625 and then demodulated with IC610 and quadrature coil L610. The audio output from the detector chip is injected to an adjustable audio gain stage and also to the noise squelch stage. The RSSI output from the detector chip is connected to an input of the A/D converter of the microprocessor for control of the predictive diversity circuit. Buffer LNA 1 st MIXER Helical Filter HPF for lowside injected 1 st LO LPF for highside injected 1 st LO 1 st LO LPF VCO From µP Controller Internal Antenna A A Internal Antenna B Predictive Diversity From microcontroller PIN Diode Switch To SAW filter