McIntosh ML1C Loudspeaker System Service Information.pdf
ML 1C LOUDSPEAKER SYSTEM SERVICE INFORMATION SERIAL NO. N1A001 AND ABOVE SPECIFICATIONS SPEAKER SIZE Woofer 12 dia. frame size (10 dia. radiator) Low mid-range 8 dia. frame size (5 dia. radiator) Upper mid-range 1-1/2 dia. dome radiator Tweeter 1-5/8 dia. coaxial super radiator CROSSOVER FREQUENCIES 250Hz, 1.5kHz, & 7kHz IMPEDANCE 8n 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 levels greater than 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 operation. The ML-4 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 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 driven at a one watt level referred to 8n. SPEAKER LOCATION REMOVE LSI TO SERVICE CROSSOVER NETWORK SCHEMATIC NOTES 3. 4. 5. 6. 7. 8. 9. 10. In some units Cl may be one single 150pF 100V capacitor. In early units L6 .15mH choke is not used. Refer to ML-1C Service Bulletin No. 2 when replacing Dome Loudspeaker. In early units C3 is two 12pF capacitors connected in series. In early units R6 was 62fi 5% 5W. In some units C2 may be two 25pF in series. In early units R3 is lOfi. See ML-1C SB No. 1 when replacing 8 loudspeaker. In early units components may be located in different positions on the crossover network board. Numbers that appear on coils are not always inductance values. In early units LS4 is 036-005 1 6fi impedance. LS4 can be replaced with 036-012 8fi impedance. Acoustic output will be the same. In some early models dome wires run through the front panel. See ML-lC SB No. 2. CROSSOVER NETWORK ro ro OJ _ CO CO CO CO cn -J .J -I -1 _i _i ASSEMBLY 044-215 NOTE 7 NOTE 9 RED | jt ORN | YEL K CO + 5 m CVJ to to 2 o o 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 power (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 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 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 hard 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. Thiswill be evident if a new mid-range has been installed and also appears to have weak or no output. Use only 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) always 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 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 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 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 20Flz 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 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 Binghamton, New York 13903 (telephone 607-723-3512) CAPAC1 TORS S ymbo1 Number Description Part Number Cl Elect. 150pF I00V 066-194 C2 Elect. 12pF 100V 066-193 C3 Elect. 6pF 100V 066-186 C4 Mylar lpF 250V 064-104 CHOKES LI Choke 3.2mH 122-136 L2 Choke 2.4mH 1 22-125 L3 Choke .6mH 122-168 L5 Choke .2mH 122-158 L6 Choke .15mH 122-167 RESISTORS R1 Wirewound 6ft 1 OW 139-087 R2 Wirewound 5ft 1 OW 139-082 R3 Wirewound 7.5ft low 139-090 R5 Wirewound 4o 10W 139-086 R6 Wirewound 56ft I0W 139-091 R7 Wirewound 6n 10W 139-087 LOUDSPEAKERS LSI 12 Woofer 036-001 LS2 8 Midrange 036-025 LS3 1-1/2 Dome Midrange 036-016 LS4 2-1/4Tweeter 036-012 MISCELLANEOUS ITEMS Terminal Red 084-086 Terminal Black 084-087 Shipping Carton 033-135 Gr i 1 1 e 030-008 Front Panel Assy. 044-339 Speaker Gasket 12 Woofer 094-092 Speaker Gasket 2-1/4 Tweeter 094-096 Speaker Gasket 1-1/2 Dome 094-100 Speaker Gasket 8 Midrange 094-094 Network Gasket 094-106 fflclntosh MclNTOSH LOUDSPEAKER DIVISION 2 CHAMBERS ST., BINGHAMTON, N.Y. 13903 ( n o SERVICE BULLETIN REPLACEMENT OF 8 LOUDSPEAKER 036-002 MODEL: ML-1C PURPOSE OF MODIFICATION: To maintain the same acoustic output. WHAT UNITS ARE AFFECTED: Serial No. N1A001 through N2A539- Serial No. L2A540 through L4A686. WHEN MODIFICATION SHOULD BE MADE: When replacing defective 036-002 8 loudspeaker. MclNTOSH MODIFICATION KIT: No kit available. PARTS REQUIRED: QUANT ITY 1 1 PROCEDURE: Step 1 Remove 12 woofer and fiberglass exposing crossover. Step 2 Locate 10ft, 10 watt resistor in series with the 8 loudspeaker. Remove and replace with 7*5ft, 10 watt resistor. Step 3 Replace fiberglass and 12 woofer. Be sure a tight caulking seal is made between the 12 woofer and the cabinet. PART NUMBER DESCRIPTION 139-090 Wirewound Resistor: 7.5ft, 10W 036-025 8 loudspeaker (over) W&mm c S.B No. 2 SERVICE BULLETIN REPLACEMENT OF 1-1/211 DOME LOUDSPEAKER 036-003 MODEL: ML-1C PURPOSE OF MODIFICATION: To maintain the same acoustic output. WHAT UNITS ARE AFFECTED: Serial No. N1A001 through N2A539. Serial No. L2A540 through L3A540. WHEN MODIFICATION SHOULD BE MADE: When replacing defective 036-003 1-1/2 dome loudspeaker. MclNTOSH MODIFICATION KIT: No kit available. PARTS REQUIRED: QUANTITY 1 1 PROCEDURE.: Step 1 Remove 12 woofer and fiberglass exposing crossover. Step 2 Locate the series capacitor. If it reads 6pF/50V NP, remove and replace with a 6pF/l00V NP capacitor. Step 3 Connect .15mH coil in series with the dome crossover. Pull yellow and black wires through hole to rear of mounting panel. Seal hole. Connect wires to dome speaker. Step 4 Replace fiberglass and 12 woofer. Be sure a tight caulking seal is made between the 12 woofer and the cab i net. PART NUMBER DESCRIPTION 036-016 1-1/2 Dome Loudspeaker 122-128 .15mH Choke (over) 038-586
