Shure m 64 a service manual
This is the 4 pages manual for shure m 64 a service manual.
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Extracted text from shure m 64 a service manual (Ocr-read)
Page 1
OPERATION lnput lmpedance (at 1 kHz) Resistance: 50 kilohms Capacitance: 160 picofarads Output Impedance (at 1 kHz) High Level: Less than 2000 ohms (minimum recom- mended load is 22,000 ohms) Low Level: 600 ohms (any load on Low Level output will not affect input clipping level) Power Consumption 5 watts Operating Voltage 120 or 240 volts ac + 1O0/0, 50160 Hz (internally selec- table) Temperature Range Operating: -7" to 57" C (20" to 135" F) Storage: -29" to 71 " C (-20" to 160" F) Dimensions See Figure 2 Net Weight 986 grams (1 Ib 2-112 oz) 144mm 104mm r(5-9/16 IN. ) 1 (4-3/32 IN.I~ OVERALL DIMENSIONS FIGURE 2 INSTALLATION To reduce the risk of fire or electric shock, do not expose this appliance to rain or extreme moisture. The M64A can be operated on any flat surface, or (with adequate space) be mounted to an amplifier chassis or cabinet using screws through the M64A's mounting flanges. The unit can be mounted in any posi- tion for normal operation, but for best results, it should be located away from motors, lighting dimmers, or other hum-producing power sources and away from intense heat sources. Should hum be encountered in a sound system or installation, one or more of the equipment power plugs may be reversed to reduce hum. If the turntable has a grounding lead, this wire can be connected to the M64A Ground screw to reduce hum pickup. WARNING Use of the M64A with power amplifiers of the transformerless (ac-dc) type may result in a shock hazard. A suitable power line isolation transformer should be used with such equip- ment. 1. Set the selector switch to the desired function (Phono, Flat or Tape). This automatically selects the proper equalization (frequency response) for both channels. 2. For the equalized Phono (RIAA) or Tape (NARTB) posi- tions, connect the signal leads from the phono car- tridge or tape head to the M64A jacks marked Chan- nel 1 lnput and Channel 2 Input. Note that the Flat position can be used for phono cartridge or tape head buffering applications in which the M64A out- put is connected to an equalized amplifier input. 3. For the Flat position using two high-impedance microphones, connect each microphone cable to one of the M64A lnput connectors. If a single high- impedance microphone is used, connect it to either lnput connector. NOTE: If low-impedance microphones are to be used, a suitable line match- ing transformer such as Shure's A95 Series should be used. 4. Refer to the phono cartridge, tape head or microphone data sheet for details on connections, phasing and grounding. 5. Connect the Channel 1 and Channel 2 Output jacks (High or Low Level) to the corresponding input jacks of the power amplifier, preamplifier, tape recorder or mixer. The High Level outputs can be connected to high-level auxiliary inputs, and the Low Level out- puts can be connected to low-level microphone in- puts (or equalized phono or tape head inputs in buf- fering applications). 6. If grounding is necessary, the associated equipment ground lead can be attached to the M64A Ground screw. 7. Insert the M64A power line cord into a proper power outlet (120 Vac +lo%, 50160 Hz), preferably one controlled by the power amplifier's on-off switch. Make certain the M64A Power switch is turned on if the unit is to be remotely turned on and off. SERVICE WARNING Voltages in this equipment are hazardous to life. Refer servicing to qualified service personnel. Balanced Line Output For professional low-impedance balanced-line use such as broadcast systems or recording consoles, an external line matching transformer such as Shure's A95 Series can be added to each M64A High Level output. The resultant output level is approximately -32 dBm. If 2
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a higher output is required (-20 dBm), the following modification can be made to increase the output level by approximately 12 dB. 1. Unplug the ac power line cord. 2. Remove the two screws securing the top cover and remove the top cover. 3. Locate the vertically mounted main printed circuit attached to the front panel. Resistors R13 and R14 (1 k, 114W, 10%) are soldered to the foil side of the board. 4. Carefully wrap and solder the leads of 330-ohm, 114W resistors across (in parallel with) the leads of R13 and R14. Use a low-wattage soldering iron and avoid contact with the circuit board or other com- ponents. 5. Replace and secure the top cover. 240 Vac Operation The M64A as supplied will operate from a 120 Vac 10%, 50160 Hz power source. For operation from a 240 Vac k lo%, 50160 Hz power source, perform the follow- ing steps. 1. Unplug the ac line cord and remove the two black self-tapping screws securing the top cover. 2. Remove the top cover. 3. Locate the voltage selector switch and move it to the 240 position. 4. Replace the ac line cord and plug (if necessary) with one designed for the 240 Vac source. If the M64A is to be used outside the U.S. and Canada, local regulations may require replacing the line cord with one having wire insulation colors as follows: "Live" or "Hot" Neutral Earth or Ground NOTE: The above modification decreases the input clipping level to approximately 25 mV. This means that U.S., Canada Black White Green Europe Brown Blue GreenlYellow if high-Out~ut cartridges Or very modulated 5. Replace the top cover and mark the rear panel to records are used, the M64A may tend to clip on loud reflect the new operating voltage. Dassaaes. If a gain increase of less than 12 dB is desire& use the following resistor values instead of 330 ohms. Gain Resistor 3 dB 2.2k 6 dB lk 9 dB 560 ohms PRINTED CIRCUIT BOARDS COMPONENT SIDE M-64 TOP SILK