M187 BELT-PACK TRANSMITTER OPERATING INSTRUCTIONS and trouble-shooting guide LECTROSONICS, INC.
INTRODUCTION Thank you for selecting the Lectrosonics M187 transmitter. This transmitter repre sents over 70 years of combined experience in the design of RF devices and sets new standards for operational convenience, flexibility and mechanical ruggedness. The M187 transmitter features all metal construction and operates on high band frequencies from 150MHz to 216MHz.
Belt-Pack Transmitter GENERAL TECHNICAL DESCRIPTION The M187 transmitter is comprised of four major functional subsystems: the input compressor, the mic preamp/gain control, the compandor, and the RF transmitter (see block diagram below). The mic preamp is an ultra-low noise type op-amp. Aside from gain control, this stage also adds high frequency preemphasis to the audio signal. This insures highest signal-to-noise ratios under varying signal conditions.
CONTROLS AND FUNCTIONS LECTROSONICS M187 ON MUTE OFF LEVEL LIMIT MIC LEVEL INPUT JACK The input on the M187 accommodates virtually every lavalier, hand-held or shotgun microphone available. Use a Switchcraft TA5F connector on the cord. See the separate sheet titled “M187 Input Jack Configuration” regard ing the correct connections for various microphones, and other sources. ON/MUTE/OFF SWITCH Turns the battery power on and off.
Belt-Pack Transmitter Since the internal circuits are all tightly regulated and the RF output stage has a separate discrete regulator, the transmitter will continue to operate to a battery voltage of 6.5 Volts. From 6.5 Volts to 6 Volts, the transmitter will still operate, but with degraded performance. Please note that a weak battery will sometimes light the POWER LED immediately after turn on, but will soon discharge to the point where the LED will go out, just like a flashlight with “dead” batteries.
BATTERY REPLACEMENT The M187 transmitter is powered by a standard alkaline 9 Volt battery. It is important that you use ONLY an ALKA LINE battery for longest life. Standard zinc-carbon batteries marked “heavy-duty” or “long-lasting” are not ad equate. They will provide only about 4 hours of operation. Similarly, ni-cad rechargeable batteries only provide 4 hours of operation or less, and will also run down quite abruptly. Alkaline batteries provide about 15 hours of opera tion.
Belt-Pack Transmitter OPERATING INSTRUCTIONS 1) Insert the microphone plug into the input jack, aligning the pins; be sure that the connector locks in. 2) Turn the power switch to the “MUTE” position on the transmitter. The “MUTE” position allows internal voltages to stabilize before audio signal paths are opened. 3) Position the microphone in the location you will use in actual operation. 4) Keeping the power switch in the “mute” position, speak as loudly as you expect you will in normal system use.
MICROPHONE CORD TERMINATION TA5F Connector Assembly 1 4 5 2 3 VIEW FROM SOLDER SIDE OF PINS 0.15" 0.3" Heatshrink Tubing Mic Cord Stripping Instructions Caution! Do not allow the shield wire to touch any metal part of the connector shell. The shield wire is the antenna on VHF models and poor operating range will result.
Belt-Pack Transmitter M187 INPUT JACK WIRING The wiring diagrams shown on the attached sheet represent the basic wiring necessary for the most common types of microphones and other audio inputs. Some microphones may require extra jumpers or a slight variation on the dia grams shown. Caution - When wiring the connector, do not use the connector body for any electrical connections. A common mistake is to use the connector body as an audio ground.
RF BYPASSING Some mics require RF protection to keep the radio signal from affecting the capsule, even though the transmitter input circuitry is already RF bypassed (see schematic diagram). If the mic is wired as directed, and you are having difficulty with squealing, high noise, or poor frequency response; RF is likely to be the cause.
Belt-Pack Transmitter TROUBLESHOOTING Before going through the following chart, be sure that you have a good battery in the transmitter the red power LED on the transmitter panel should glow brightly. SYMPTOM POSSIBLE CAUSE TRANSMITTER BATTERY LED OFF 1) Battery is inserted backwards. 2) Battery is dead. NO TRANSMITTER MODULATION LEDs 1) Gain control turned all the way down. 2) Battery is in backwards. Check power LED. 3) Mic capsule is damaged or malfunctioning.
SPECIFICATIONS AND FEATURES Operating frequencies: 150 to 216 MHz RF Power output: 50 mW Deviation: ±15kHz (max) Spurious radiation: 55 dB below carrier Equivalent input noise: -126 dBV Input level: Nominal 2 mV to 300 mV (before compression) 30 Volt max.
Belt-Pack Transmitter SERVICE AND REPAIR If your system malfunctions, you should attempt to correct or isolate the trouble before concluding that the equipment needs repair. Make sure you have followed the setup procedure and operating instructions.
LIMITEDONE ONE YEAR LIMITED YEARWARRANTY WARRANTY The equipment is warranted for one year from date of purchase against defects in materials or workmanship provided it was purchased from an authorized dealer. This warranty does not cover equipment which has been abused or damaged by careless handling or shipping. This warranty does not apply to used or demonstrator equipment. Should any defect develop, Lectrosonics, Inc.
