The minimoog MODEL D TECHNICAL SERVICE MANUAL by R. J. Folkman CONTROLLERS OSCILLATOR BANK MIXER MODIFIERS moog MUSIC INC.
MINI-MOOG Field Service Manual CONTENTS Section I Title Page Precautionary Measures 2 II Sub-assembly Descriptions 3 III Block Diagram 5 IV Trouble Analysis Guide 6 V Sub-assembly Locations 8 Cover Removal and Sub-assembly Replacement 9 VI VII VIII IX X XI XII XIII Adjustment Procedures and Locations 10 Keyboard Maintenance 14 Schematic Diagrams 15 Component Location Charts 16 Replacement Parts 17 Modifications 18 Ordering and Shipping Instructions 19 Service Department Pol
Section I: Precautionary Measures In the Mini-Moog, as in any electrical device, shock hazards exist. All lethal voltages are confined to the area around the power switch and the A.C. fuseholder. Always unplug the instrument while servicing the electronics. Keyboard cleaning and adjusting may be done with the unit turned on. When a fuse blows, replace it only with the proper size as indicated on the label directly below the fuseholder.
Section II: Sub-assembly Description 93-113 Oscillator (Board 1) This assembly contains three tone oscillators, summing amplifiers, exponential current generators, waveshaping circuits and a -5 volt reference source. The three oscillators are independent and non-synchronous. Each oscillator is voltage controlled from external sources such as the keyboard. Linear input voltages are converted to exponential currents which are used to control the frequency or pitch of the tone produced.
The external pre-amp is a three transistor high-gain amplifier. The output of the pre-amp is monitored by an overload indicator. The overload driver circuit is a Schmitt trigger which turns the overload light on when external signal levels become excessive. The first and second voltage controlled amplifiers are two nearly identical circuits. Their gain is controlled by varying the voltage which supplies the current source transistors. A buffer or output amplifier follows the second VCA stage.
Section III: Block Diagram (This block diagram is a simplified version of the one from the User’s Manual. The diagram from the service manual fits on a single 11"x17" sheet.
Section IV: Trouble Analysis Guide Use this chart along with the block diagram (Section III) to determine which assembly or component is defective. MALFUNCTION PROBABLE CAUSE AND CURE Unit dead (no pilot light) 1. Blown A.C. fuse 2. Defective power switch 3. Defective line cord or plug Unit dead (pilot light on, overload light off) 1. Defective power supply (board 3) 2. Defective power transformer 3. Defective output amplifier (change filter board 4) Unit dead (pilot light and overload light on) 1.
MALFUNCTION PROBABLE CAUSE AND CURE Excessive drift or pitch change after key is released (greater than 1 semitone per minute) 1. Defective keyboard circuit (replace board 2) Loudness and/or filter contour generator operate improperly 1. Defective contour generator (board 2) No output at phones headphone jack (main output normal) 1. Monaural plug in stereo jack 2. Defective headphone amp (replace power supply board 3) Overload light fails to operate when excessive signal is applied 1.
3-118 Rectifier -9- 93-116 (Bd. 4) Filter 93-115 (Bd. 3) Power Supply 93-061 Keyboard 93-113 (Bd. 1) Oscillator 93-114 (Bd. 2) Contour Gen.
Section VI: Cover Removal and Sub-assembly Replacement In order to service the Mini-Moog circuitry, it is necessary to remove the rear cover assembly. CAUTION: Be sure the unit is unplugged before removing the cover. Remove 18 screws (5 top, 5 lower back, and 4 each end of cover); then lift the cover off. Circuit boards are plugged into sockets at the bottom and secured at the top with two mounting screws. To remove a circuit board, first remove the screws then unplug from the connector.
Section VII: Adjustment Procedures and Locations Each time a Mini-Moog is serviced, it should be tuned. When a board has been replaced it will be necessary to make additional adjustments. Refer to the table below to determine which adjustments must be made according to the board that has been replaced. WHEN REPLACING MAKE THESE ADJUSTMENTS 93-113 (Board 1) Oscillator 1. Oscillator 1, 2, and 3 tuning 2. Octave range trimmer 93-114 (Board 2) Contour Generator 1.
ADJUSTMENT PROCEDURES NOTE: The tuning and other functions rely heavily on accurate power supply voltages. Always be sure the + and - 10 volt supplies are properly set before making other adjustments. * Digital voltmeter with 0.1% accuracy TO ADJUST . . . FOLLOW THIS PROCEDURE . . . +10 volts Connect an accurate D.C. voltmeter* to pins 1A and 2A on the oscillator (board 1). Adjust the +10 volt trimpot on the power supply (board 3) for +10.00 volts. -10 volts Connect an accurate D.C.
TO ADJUST . . . FOLLOW THIS PROCEDURE . . . Oscillator Tuning (Without Equipment) "Visualign" Turn all MIXER switches off. Set MIXER VOLUMES at 1. Turn on MAIN OUTPUT switch and set OUTPUT VOLUME to 8. Set ATTACK and DECAY times to 0, SUSTAIN to 10. Turn FILTER MODULATION and KEYBOARD CONTROL switches off. Set EMPHASIS and AMOUNT OF CONTOUR to 0. Set PITCH WHEEL to center, TUNE control to 0, RANGE switches to 2 ft., WAVEFORM switches to TRIANGLE.
TO ADJUST . . . FOLLOW THIS PROCEDURE . . . Regeneration Cal. Turn all MIXER switches off. Monitor output with headphones. Set CUTOFF FREQUENCY control to -1. Insert an S-Trigger plug. Rotate EMPHASIS control clockwise. Regeneration should start when the EMPHASIS control is between 7 and 8. If it does not, set EMPHASIS control to 7.5 and rotate the Regeneration Cal. trimpot (on filter board) slowly clockwise until regeneration starts. Filter Range Turn KEYBOARD CONTROL switches 1 and 2 off.
Point "A" 910 K Fig. 1 - 15 - Range Oct Range Trimmer Osc. 3 Osc. 2 Osc.
-10 V. Adjust +10 V. Adjust Noise Level 93-115 Power Supply: Adjustment Locations Fig.
A-440 33 K 2nd VCA Point "A" 1st VCA Regen. Cal. Filter Scale Filter Range 93-116 Filter: Adjustment Locations Fig.
Section VIII: Keyboard Maintenance Occasionally it will become necessary to clean and adjust the keyboard. The contacts, although gold plated, may become dirty, contaminated, or corroded. When contacts become poor, noises and erratic sounds may be generated while playing the instrument. To service the keyboard, the bottom cover must be removed. This cover is held on with 8 wood screws. If the keyboard compartment is found to be excessively dirty, it should be blown out with air first.
Section IX: Schematics (The circuit schematics are not available at this time.
Section X: Component Locations (The component location diagrams are not available at this time.
Section XI: Replacement Parts Moog Part Number Description 93-113 93-114 93-115 93-116 93-060 93-061 99-104 95-570 74-004 57-051 57-026 53-110 43-160 37-010 61-112 57-004 57-001 53-002 53-003 53-021 53-107 65-005 51-20X 93-067 94-001 94-002 94-004 Board No. 1 Oscillator Board No. 2 Contour Generator Board No. 3 Power Supply Board No.
Section XII: Modifications 93-113 Oscillator Assembly (Board 1) To improve tracking and pitch stability on Mini-Moog oscillator boards with serial numbers above 1300, make the following changes: 1. 2. 3. 4. 5. 6. Change R-69, R-105, and R-141 from 6.8K to 15K 1/2 W 5% carbon Replace R-78, R-106, and R-128 with RC Network, part number 65-032 Change R-181 from 56K to 51K 1/2 W 5% carbon Change R-170 from 15K 5% to 15K 1% Metal Film Change R-162 from 3K 5% to 3.
Section XIII: Ordering and Shipping Instructions Ordering Parts Most commonly used parts are listed in Section XI. When ordering, please include the Moog part number. If the part is not listed, order by description. Be as accurate as possible when describing what you want. Example: or: Transistor, Q8 on board 2 Control, amount of contour Returning Parts All parts being returned should be accompanied with a "Return Material Tag".
MOOG MUSIC, INC. SERVICE DEPARTMENT POLICY MINIMUM CHARGE (for non-warranty service) − is 1 hour ($15.00). Additional charge per 1/2 hour ($7.50). Update parts are free; all other parts are charged to the customer. WARRANTY ON REPAIR − is issued as of date stamped on pink copy; only for parts or malfunction repaired. Warranty period is 90 days−we pay shipping both ways. DEALER WARRANTY SERVICE − is to be reimbursed when we receive copy of his Service Report and defective components in the amount of $10.
