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Micro-Tech 1200 Amplifier Service Manual
POWER AMPLIFIER
SERVICE MANUAL
®
MICRO-TECH -1200
©1995 by CROWN INTERNATIONAL, INC.
Mailing Address: Shipping Address:
P.O. Box 1000 57620 C.R. 105
Elkhart, IN U.S.A. 46515-1000 Elkhart, IN U.S.A. 46517
® ® ®
Micro-Tech , ODEP and Crown are registered trademarks of Crown International, Inc.
K-SVCMT12
8-95
1
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Micro-Tech 1200 Amplifier Service Manual The information furnished in this manual does not include all of the details of design, production, or variations of the equipment. Nor does it cover every possible situation which may arise during installation, operation or maintenance. If you need special assistance beyond the scope of this manual, please contact the Crown Technical Support Group. Mail: P.O. Box 1000 Elkhart IN 46515-1000 Shipping: 57620 C.R. 105 Elkhart IN 46517 Phone: (800) 3
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Micro-Tech 1200 Amplifier Service Manual Table of Contents Introduction ............................................................. 4 Scope ...................................................................... 4 Warranty .................................................................. 4 Parts Information ..................................................... 5 Specifications .......................................................... 6 Voltage Conversion ......................................
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Micro-Tech 1200 Amplifier Service Manual Introduction This manual contains service information on Crown circuit board may be built up with different parts to power amplifiers. It is designed to be used in conjunc- create different modules. Note that Crown does not tion with the applicable Owner's Manual. However, sell blank (unpopulated) circuit boards. some important information is duplicated in this Ser- vice Manual in case the Owner's Manual is not readily Each of the compact audio power am
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Micro-Tech 1200 Amplifier Service Manual Parts Information shipment on a C.O.D. or pre-payment (check or credit GENERAL INFORMATION card) basis. Later sections include both mechanical and electrical parts lists for this product. The parts listed are current TERMS as of the date printed. Crown reserves the right to modify and improve its products for the benefit of its Normal terms are pre-paid. Net-30 Days applies to customers. only those firms having pre-established accounts with Crown. If pre-
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Micro-Tech 1200 Amplifier Service Manual Specifications Unless noted otherwise, all specifications are based Input Impedance: Nominally 20K ohms balanced; 10K on driving an 8 ohm load per channel, both channels ohms unbalanced. driven, the sensitivity switch in the 26dB position, the AC supply is 120VAC at 60Hz. Crown specifications Output Impedance: <10 milliohms in series with <2 are guaranteed through the warranty period (normally microhenries. 3 years). Because our testing methods are more s
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Micro-Tech 1200 Amplifier Service Manual Voltage Conversion The 120 Volt 60 Hz version, sold in the United States, is not voltage selectable. It does not have voltage selection boards. This version is to be used only with 120 Volts and only with 60Hz. All other versions of the Micro Tech 1200 use voltage selection boards. The following chart indicates which jumpers are used for different voltages. Note that the fuses and transmotor may need to be changed to accommodate different voltages. Versio
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Micro-Tech 1200 Amplifier Service Manual Theory packaging of this model is designed for maximum OVERVIEW watt/price/weight/size value with user friendly fea- It should be noted that over time Crown makes im- tures. provements and changes to their products for various reasons. This manual is up to date as of the time of For additional details refer to the specification section, writing. For additional information regarding these or to the applicable Owner’s Manual. amplifiers, refer to the applic
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Micro-Tech 1200 Amplifier Service Manual Theory amplifies the difference between input and output The ODEP transistors steal drive as dictated by the signals, any difference in the two waveforms will ODEP circuitry (discussed later). The control/protec- produce a near open loop gain condition which in turn tion transistors act as switches to totally shunt audio to results in high peak output voltage. The output of the ground during the turn-on delay, or during a DC/LF or Error Amp, called the Er
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Micro-Tech 1200 Amplifier Service Manual Theory to the cutoff level under static (no signal) conditions. High Side (HS) This is because PNP devices require greater drive The High Side (HS) of the bridge operates much like current. a conventional bipolar push-pull output configuration. As the input drive voltage becomes more positive, the HS bias is regulated by Q18, the Bias Servo. Q18 is a HS NPN conducts and delivers positive voltage to the Vbe multiplier which maintains approximately 3.3V loa
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Micro-Tech 1200 Amplifier Service Manual Theory respect to each other. This allows the power supply to deliver +Vcc and -Vcc from the same bridge rectifier Low side bias is established by a diode string which and filter as a total difference in potential, regardless also shunts built up charges on the output devices. of their voltages with respect to ground. The LS uses Bias is adjustable via potentiometer. Flyback diodes inverted feedback from the HS output to control the perform the same funct
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Micro-Tech 1200 Amplifier Service Manual Theory POSITIVE +VOLTAGE +LVA HIGH SIDE TRANSLATOR -1 OUTPUT NPN STAGE ERROR BGS VGS AMP OUTPUT HIGH SIDE DEVICE BALANCED -1 BIAS EMULATION INPUTS SERVO PROTECTION NEGATIVE -VOLTAGE -LVA HIGH SIDE TRANSLATOR -1 OUTPUT PNP STAGE MAIN NEGATIVE FEEDBACK (NFb) LOOP POSITIVE LOW SIDE OUTPUT NPN STAGE LOW SIDE BIAS -1 DIODE STRING NEGATIVE LOW SIDE INVERTING OUTPUT BRIDGE PNP STAGE BALANCE Figure 3. Typical Crown Amplifier Basic Block Diagram (One Channel Shown
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Micro-Tech 1200 Amplifier Service Manual Electrical Checkout Procedures GENERAL INFORMATION TEST 3: ODEP VOLTAGE ADJUSTMENT The following test procedures are to be used to verify Spec: Bias Per Chart, ±0.1V DC. operation of this amplifier. DO NOT connect a load or Initial Conditions: Controls per standard, heatsink at inject a signal unless directed to do so by the proce- room temperature 20 to 30°C (68 to 86°F). Note: This dure. These tests, though meant for verification and adjustment should n
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Micro-Tech 1200 Amplifier Service Manual Electrical Checkout Procedures Spec: Level controlled by level controls. TEST 4: AC POWER DRAW Initial Conditions: Controls per standard. Spec: 100 Watts maximum quiescent. Procedure: No Load. Inject a 1 kHz sine wave. With level Initial Conditions: Controls per standard. controls fully clockwise you should see full gain. As Procedure: With no input signal and no load, measure controls are rotated counterclockwise, observe similar AC line wattage draw. I
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Micro-Tech 1200 Amplifier Service Manual Electrical Checkout Procedures Spec at 4 Ohm Stereo: >= 470W at 0.1% THD. Spec at 2 Ohm Stereo: >= 600W at 0.1% THD. International 8 Ohm Stereo: >=305W at 0.1% THD. International 4 Ohm Stereo: >=430W at 0.1% THD. International 2 Ohm Stereo: >=535W at 0.1% THD. Initial Conditions: Controls per standard. Procedure: Load each channel to 8 ohms. Inject a 1 kHz sine wave and measure at least 50.60 VAC at the output of each channel. Load each channel to 4 ohms
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Micro-Tech 1200 Amplifier Service Manual Electrical Checkout Procedures Spec: No dangerous transients. Initial Conditions: Controls per standard. Procedure: From an on condition, turn off the amplifier and monitor the output noise at the time of turn off. Note: Turn off noise may increase significantly if the amplifier is cycled off and on. TEST 19: INTERMODULATION DISTORTION Spec at 0 dB Output: 0.01%. Spec at –35 dB Output: 0.05%. Initial Conditions: Controls per standard. Procedure: Load each
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Micro-Tech 1200 Amplifier Service Manual Parts List (Non-Module) SUPPLIMENTAL ITEMS CPN ITEM QTY D 4137-2 Nylon Thumbscrew Washer 4 C 3342-0 Feet, Black Self-Stick 4 A10087-71012 10-32 .75 Machine (Rack Screw) 4 K80583-6 MT Series Owners Manual 1 POWER SUPPLY CPN ITEM QTY M43534-3 MT Fuse Board Assembly (120V, 60Hz Units Only) 1 D 8069-4 Fuse Board Insulator 1 Q42867-4 Fuse Module, Ch 1 (50-60 Hz Units) 1 Q42866-6 Fuse Module, Ch 2 (50-60 Hz Units) 1 A10285-28 20 Amp Fuse (100-120V Units) 2 A102
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Micro-Tech 1200 Amplifier Service Manual Parts List (Non-Module) OUTPUT ASSEMBLY (CONT.) CPN ITEM QTY (ONE PER CHANNEL) D 8774-8 PTC, 95 Deg. Thermal Sensor 1 F12019-0 Aluminum Heatsink Slug (under diodes on output mod) 1 C 8813-5 MPS8097/MPSA18 NPN Transistor (Q318/Q418) 1 B 5842-8 #23 Tubing for Q318/Q418 transistor leads Order in inches C 5826-0 LM-234Z-6 Thermal Sense (S100/S200) 1 B 5464-1 #24 Teflon Tubing for S100/S200 Order in inches C 8573-5 2SA1186 Power Transistor, PNP Driver (TO3P) 2
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Micro-Tech 1200 Amplifier Service Manual Parts List (Non-Module) MAIN CHASSIS ASSEMBLY (CONT.) CPN ITEM QTY. A10110-70605 Screw, 6-32-.312 Taptite Ph (Covers) 20 A10086-70806 8-32 x .37 Screw 3 A10094-3 #6 Internal Star Washer 3 A10094-6 #8 Internal Star Washer 4 A10094-8 #10 Internal Star Washer, Zinc 12 A10099-7 #10 Nylonb Shoulder Washer 8 A10100-16 7/16OD x .203ID Washer 8 A10102-8 10-32 Hex Nut 12 A10109-10822 8-18 x 1.375 Pan Head Screw 2 A10110-70812 8-32 x .750 Taptite Pan Head Screw 2 A
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Micro-Tech 1200 Amplifier Service Manual Module and Schematic Information MODULE HISTORY FUSE MODULE: The Micro Tech 1200 amplifier was introduced in M43534-3 (120V 60Hz U.S. Units Only) January 1986. Since then there have been several Fuse module on P10391-4 board. updates and revisions, some of which called for new Q42866-6 -Channel 2 (Universal Volt Units Only) modules. The following is a list of all modules used up Fuse module on P10296-5 board. to this date, August 1995. Q42867-4 -Channel 1
