Summary of Contents for Synthesis Technology MOTM-485 GX-1 Diode VCF
- Page 1 MOTM-485 GX-1 Diode VCF Assembly Instructions & Owner’s Manual Synthesis Technology 6625 Quail Ridge Dr. Fort Worth, TX 76180 (817) 498-3782 www.synthtech.com Aug. 11, 2005...
- Page 2 Q3, Q4, Q9 2ea BC560C PNP transistor Q2, Q6 2ea CA3086 transistor array IC Q7, Q10 1ea BF245 FET transistor 1ea LT1013 op amp 1ea THAT 340P transistor array 1ea SSM2220P PNP array SYNTHESIS TECHNOLOGY PAGE 2 MOTM-485 ASSEMBLY 8/11/05 WWW.SYNTHTECH.COM...
- Page 3 4ea #6-32 x ½” zinc screws (for attaching pc board to bracket) 4ea ¼” aluminum spacers 4ea #6 KEPS nuts (for pc board) 5ea small tie-wraps Organic Solder AND No-Clean solder (1 bag each type) SYNTHESIS TECHNOLOGY PAGE 3 MOTM-485 ASSEMBLY 8/11/05 WWW.SYNTHTECH.COM...
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Page 4: General Information
The 1% resistor color bands can be confusing, so always measure them with the DVM before soldering. VERIFY THE PARTS LIST Verify that all of the parts are in the kit as shown on the parts list. SYNTHESIS TECHNOLOGY PAGE 4 MOTM-485 ASSEMBLY 8/11/05 WWW.SYNTHTECH.COM... - Page 5 Locate the 100K 1% resistors (9) and solder into R1 to R6 (all near U1), R14 (by J3), R28 (by Q7) and R35 (by VR3). Locate the 4K7 resistors (5) and solder into R33 (by C6), R41-43 (by TP2) and R46 (by SW2A). SYNTHESIS TECHNOLOGY PAGE 5 MOTM-485 ASSEMBLY 8/11/05 WWW.SYNTHTECH.COM...
- Page 6 Locate the 47-ohm and solder into R48 (by Q8). Leave the Tempco resistor for a later step. After soldering all the resistors wash and dry the pc board. PART #2: Soldering the ICs & Misc parts SYNTHESIS TECHNOLOGY PAGE 6 MOTM-485 ASSEMBLY 8/11/05 WWW.SYNTHTECH.COM...
- Page 7 Wash the board in warm water, gently scrubbing both sides. Shake the board a couple of times, blot dry with an old towel (the leads will frazzle a good towel). Let dry at least 15 minutes. SYNTHESIS TECHNOLOGY PAGE 7 MOTM-485 ASSEMBLY 8/11/05...
- Page 8 Q1 and the Tempco is placed so that the DIP package is in contact with the bottom of the Tempco. Be sure the Tempco is level and flat before soldering. SYNTHESIS TECHNOLOGY PAGE 8 MOTM-485 ASSEMBLY 8/11/05...
- Page 9 Solder the 2 short coax cables into locations J5 and J6. Secure with tie-wrap. Solder the long white/black twisted wire into J3. White into 1, Black into 2. Solder the orange/white twisted wire into J1. White into 1 and Orange into 2. SYNTHESIS TECHNOLOGY PAGE 9 MOTM-485 ASSEMBLY 8/11/05...
- Page 10 VR1-V3 (on the front of the panel) and tighten. This will “pull” the pcb up against the panel, resting on the 3 rear pot nuts. NOW you tighten the 4 nuts on the bottom of the pcb bracket. SYNTHESIS TECHNOLOGY PAGE 10 MOTM-485 ASSEMBLY 8/11/05...
- Page 11 Use the remaining tie-wrap to bundle the wires to the jacks. Rotate all of the front panel pots fully counter-clockwise. Locate the KNOBS. Notice each knob has a white line on it. Place the knob on the pot shaft, SYNTHESIS TECHNOLOGY PAGE 11 MOTM-485 ASSEMBLY 8/11/05...
- Page 12 “I” there is a resultant voltage “V” on the curve. Taking the basic electrical formula V=I x R (voltage = current times resistance), rewriting it as V/I=R the “apparent” SYNTHESIS TECHNOLOGY PAGE 12 MOTM-485 ASSEMBLY 8/11/05...
- Page 13 Rq as the R23+R37+TP1+C9+Q7 chain. Yes, there is a capacitor in there (never mind a transimpedance diode cell made from Q7) but we’re dealing with AC impedance so think of it as a resistor. It is much easier that way. The op-amp? We’ll get to that. SYNTHESIS TECHNOLOGY PAGE 13 MOTM-485 ASSEMBLY 8/11/05...
- Page 14 (see the MOTM- 300/310) in that 1) it does not use a servo loop and 2) it uses a PNP-NPN configuration as SYNTHESIS TECHNOLOGY PAGE 14 MOTM-485 ASSEMBLY 8/11/05...
- Page 15 Slowly rotate the FREQ knob towards 10. At first, the volume should be very low because the VCF (if it is working) will be attenuating most of the signal. As you rotate the FREQ knob, more and more of the signal should pass through. SYNTHESIS TECHNOLOGY PAGE 15 MOTM-485 ASSEMBLY 8/11/05...
- Page 16 Quirk #3: limited sweep range The filter cannot sweep 20Hz-24Khz like say a MOTM-440. The MOTM-485 is more on the order of 80Hz to 6Khz. Again, this is a function of the diode control currents. SYNTHESIS TECHNOLOGY PAGE 16 MOTM-485 ASSEMBLY 8/11/05...
- Page 17 You can play with the filter caps. C10 and C11 must be the same, and C12 has to be 2 times C10/C11. If you still cannot get the module to perform correctly, please contact us by phone at (817) 498-3782 or by email to synth1@airmail.net SYNTHESIS TECHNOLOGY PAGE 17 MOTM-485 ASSEMBLY 8/11/05 WWW.SYNTHTECH.COM...
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Page 18: Specifications
SPECIFICATIONS MOTM-485 GX-1 Diode VCF Audio Input Range 10V pk-pk nom. combined both inputs Control Voltage Range -7V/+7V Output impedance 1000 ohms, nom. Frequency Range 80Hz – 6Khz nom. CONTROLS FREQ sets filter cutoff frequency sets resonance CV MOD reversing attenuator for filter cutoff...
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