McIntosh ML2C Loudspeaker System Service Information Late Production.pdf

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1、ML 2C LOUDSPEAKER SYSTEM SERVICE INFORMATION SERIAL NO. L3C225 AND ABOVE BC4187 AND ABOVE 38-843 SPECIFICATIONS SPEAKER SIZE Woofers two 12 dia. frame size (10 dia. radiators) Low mid-range 8 dia. frame size (5 dia. radiator) Mid mid-range 1-1/2 dia. dome radiator High mid-range 1-1/2 dia. dome radi

2、ator Tweeter 1-5/8 dia. coaxial super radiator CROSSOVER FREQUENCIES 250Hz, 1.5kHz, 3kHz, & 7kHz IMPEDANCE 8fl Nominal POWER HANDLING: Sine Wave steady state SINE WAVE POWER LIMIT IN WATTS FREQUENCY IN Hz Avoid operating the speaker system with sustained sine wave signals at power level greater than

3、 the indicated limits. Permanent damage may result. POWER HANDLING: Program Material High energy peaks normal to orchestral music are easily and faithfully reproduced by the speaker system. These peaks are of relatively short duration and do not produce the heating effect caused by sustained tone op

4、eration. The ML-A speaker system will handle up to 300 watts of orchestral music program material. Care must be taken, however, to use a power amplifier that has an adequate power rating If a low power amplifier is used, the loudest passages may be clipped by the amplifier. This clipping will cause

5、the speaker to sound distorted. The large harmonic content of a badly clipped signal can cause excessive heating and re sulting damage to the high frequency speaker elements and crossover network. OUTPUT LEVEL In a reverberant room the system will nominally produce an 89dB sound pressure level when

6、driven at a one watt level referred to 8fl. SPEAKER LOCATION REMOVE REAR PANEL TO SERVICE CROSSOVER NETWORK SCHEMATIC NOTES . In early units C4 is 3.3pF. 2. In early units LS6 is 036-005 16n impedance. LS6 can be replaced with 036-012 8fi impedance. Acoustic output will be the same. CROSSOVER NETWOR

7、K TWO DIFFERENT CIRCUIT BOARDS HAVE BEEN USED THE SCHEMATIC IS THE SAME FOR BOTH. ASSEMBLY 044-449 SYSTEM SCHEMATIC SERVICE NOTES Speaker element failure can be quickly located by using FM hiss at a low power level. Listen at each speaker to verify if all the speakers are at least working. A low pow

8、er (1-5 watt) sine wave sweep 20-20kHz can be used as a quick check for distortion. A speaker element with obvious distortion must be replaced. To determine if the speaker element is dead, remove the speaker and momentarily connect a 1.5 to 6V battery across the terminals. If no sound is heard, the

9、speaker element must be replaced. The crossover network must be inspected when burned out speaker elements are replaced. The net work must also be inspected if a speaker element produces sound with the battery test but does not play when connected in the system. The woofer must be removed to get to

10、the crossover. Check for bad connections, broken wires, etc. Be sure to check the resistors mounted on the plate underneath the printed circuit board. A broken lead on these resistors can also be the cause of intermittent or partial failure of the system. When a system has been driven excessively ha

11、rd by a clipped amplifier for long periods of time, the dome mid-range may appear to have weak or no output. In addition to a burned out mid-range, the 7pF capacitor may also be damaged. Th is wi11 be evident if a new mid-range has been installed and also appears to have weak or no output. Use only

12、McIntosh replacement capacitors. These have been specially selected for low ESR. Use RTV silicone rubber under replacement parts mounted on the printed circuit board. In addition to the solder connections, this insures a vibration free bond to the board. The solid colored wire (other than black) alw

13、ays goes to the red marked terminal on the speaker. This is the positive terminal. If the polarity of a speaker is unknown, momentarily connect a 1.5 to 6V battery to the terminals. When the cone moves away from the magnet, it means the + terminal of the battery is connected to the + terminal of the

14、 speaker. When installing speakers or crossover network in the cabinet, care must be taken to insure a tight air seal to the cabinet. Replace the black caulking material or foam gasket if necessary. Mortite caulking compound or equivalent could be substituted but care must be taken that it will not

15、be visible after the part is installed. If a woofer screw strips out in the wood of the cabinet, the speaker can be rotated and new mounting holes drilled. After the system is reassembled, it must be checked for air leaks. This can be done by putting a 20Hz sine wave into the system at 50 watts (20

16、volts). By listening around the speakers closely for hissing sounds, areas can be located that must be sealed. The system must also be swept from 20Hz to 250Hz at 25 watts (14 volts) to insure there are no vibrations due to wires hitting the woofer cone, etc. All defective parts must be packed well

17、and returned to McIntosh Laboratory Loudspeaker Division. REPLACEMENT PARTS All parts not listed are common items obtain able from radio parts jobbers. Replacement parts may be obtained when ordered by PART NUMBER from: McIntosh Laboratory, Inc. Customer Service Department 2 Chambers Street Binghamt

18、on, New York 13903 (telephone 607-723-3512) CAPACITORS Symbol Number Description Part Number MISCELLANEOUS ITEMS Cl Elect. 50pF 100V 066-192 Terminal Red 084-086 C2 E1ect. 25pF 100V 066-189 Terminal Black 084-087 C3 Mylar 6pF 100V 064-114 Shipping Carton 033-127 C4 Mylar 3.3pF 100V 064-117 Grille 03

19、0-012 C5 Mylar lpF 250V 064-104 Front Panel Assy. 044-312 CHOKES Speaker Gasket 12 Woofer 094-092 LI Choke 5mH 122-124 Speaker Gasket 2-1/4 Tweeter 094-096 L2 Choke 2,4mH 122-125 Speaker Gasket l-l/2Dome 094-100 L3 Choke .3mH 122-122 Speaker Gasket 8 Midrange 094-094 L4 Choke .4mH 122-127 Network Ga

20、sket 094-106 L5 Choke . 5mH 122-126 L6 Choke . 2mH 122-123 L7 Choke . 15mH 122-128 RESISTORS R1 ,2 Wirewound 7.5n 10W 139-090 R3 Wirewound ion low 139-089 R4 Wirewound 4l2 10W 139-086 R5 Wirewound 2n 10W 139-085 R6,7 Wirewound 4n 10W 139-086 R8 Wirewound Is 10W 139-084 LOUDSPEAKERS LSI ,2 12 Woofer

21、036-001 LS3 8 Mi drange 036-025 LS4,5 1-1/2 Dome Midrange 036-016 LS6 2-1/4 Tweeter 036-012 McIntosh McIntosh loudspeaker division 2 CHAMBERS ST., BINGHAMTON, N.Y. 13903 SERVICE BULLETIN ML-2C/2M S.B. No. 1 REPLACEMENT OF 8 LOUDSPEAKER 036-002 MODEL: ML-2C and ML-2M Loudspeakers. PURPOSE OF MODIFICA

22、TION: To maintain the same acoustic output. WHAT UNITS ARE AFFECTED: ML-2C Serial No. L1C001 through L1C429- ML-2M Serial No. L1D001 through L1D145. WHEN MODIFICATION SHOULD BE MADE: When replacing defective 036-002 8 loudspeaker. MclNTOSH MODIFICATION KIT: No kit available. PARTS REQUIRED: QUANT IT

23、Y 1 1 PROCEDURE: Step 1 Remove rear panel. Step 2 Locate lOfi, 10 watt resi 8 loudspeaker. Remove 10 watt resistor. stor in ser i and replace i es with the with 7.5, Step 3 Replace rear panel. PART NUMBER DESCRIPT ION 139-090 036-025 Wirewound Resistor: 75ft, 1OW 8 Loudspeaker (over) McIntosh Laboratory Incorporated 2 Chambers Street Binghamton, New York 13903 Phone: Area Code 607-723-3512 + o- 25j io xi -ii i ,REPLACE i WITH 7.5X1 l l- LOUDSPEAKER 038-587