MOTM-320 User Manual
Contents
1. ChT gu d 2 Dec 1999 16 25 00 SYNTHESIS TECHNOLOGY PAGE 18 MOTM 320 ASSEMBLY 9 12 2011 WWW SYNTHTECH COM USE THE MOTM 320 LFO LFOs are used to modulate VCOs vibrato VCAs tremelo and filters In MOTM system you can use your MOTM 320 to trigger the 700 to use as one input of a MOTM 110 Ring Mod or a host of other uses The unique SHAPE feature can add another dimension to your audio palette The following scope screens show the effect of the SHAPE control as it is rotated throughout it s range Remember the SHAPE pot is like the initial shape as any external control voltage plugged into the SHAPE jack is treated as an offset to the pot In other words a negative voltage 16 like turning the pot lower and a positive voltage 15 like turning the pot higher There is no input attenuator so any applied SHAPE voltage is full strength into the summer circuit Also note that the SHAPE modifies all 4 outputs simultaneously And it is possible to cause the PULSE output to go to the extremes 0 and 100 duty cycle which is a constant DC voltage To sync the LFO apply a minimum 8V pk pk zero crossing signal into the sync jack Any pulses applied must be at least 5ms in duration It is possible to sync the LFO to pulses that are 0 to 5V such as outputs of 74HC logic devices Since the sync is a hard reset of the triangle integrator appl2. 18 TNI ik DE ven LTISSSUN I ast t ast xot ast E J ast NZ ast 2 coena ast Occ ven 90 xor 7 vex s z i 2 0 mi 5 CH NI DNAS ve AST sza ast zza ova ma ES ve l ast ST AST aste Toa ast ET E ast ota 2 AT zo Dossou 5 MOOT zu 5 wor moral g Loi vu 25 aS 15 gt T xoot HIIWHHSH POE UM gt zT Lo ast I WI AST TE AST U v eo vun LOO AT 2 lt Jd 62 IN soa ASE MOOT NtoO Lp L c 9 G
3. Use ONLY warm water SYNTHESIS TECHNOLOGY PAGE 9 MOTM 320 ASSEMBLY 9 12 2011 WWW SYNTHTECH COM PART 7 MISC and IC STUFF Almost done with the parts on the pc board This will finish up the soldering with the organic flux o u n Locate the MISC 1 bag and the IC bag Locate the ferrite beads 2 They are axial parts gray colored with no markings These are non polar and are soldered into L1 and L2 by JP1 Locate the 1N4148 diodes 4 Note one end has a black band around it This 1s the cathode end Look at the pc board the 4 diode locations D1 D4 show this banded end Insert the 4 diodes the board with the cathode end over the band on silkscreen Note that all 4 diodes point in the same direction Locate the 074 amp Solder into U1 Note that all ICs are pointing down towards the bottom edge of the pc board The IC will have a notch or indentation in the top by Pin 1 Locate the LM393 comparator Solder into U2 Locate the NE5517 OTA Solder into U4 Locate the TL072s 8 Solder into U3 U6 and U7 Locate the CA3080AE and solder into U8 Locate the OP275 It solders into U5 Note Revision A pe boards show this part on the silkscreen as a 4556 This is a typo the OP275 is the correct part Locate the BC550C transistors 7 Remove transistors from the tape carrier and any residue from the holding tape Match the flat side of the part to the fl
4. GROUND USUALLY WITH THE BRAIDED CONDUCTOR Each jack has a flat washer a lockwasher and a hex nut Remove the nuts and washers from each jack Place aside Keep the lockwasher on the jacks Insert the 8 jacks lockwashers with the beveled corner in the upper right corner into the 8 holes Place the flat washer on the jack then the hex nut Hold the jack with one hand on the backside keeping it square Tighten the hex nut with a nut driver NOTE when tight not much of the exposed threads of the jack are exposed You are now ready to attach the pc board to the bracket and then wire up to the panel PART 8 ATTACH PC BOARD TO BRACKET PANEL In the HARDWARE bag locate 4 6 32 x 1 2 screws 6 6 KEPS nuts and 4 Spacers Locate the mounting bracket The pc board attaches to the bracket with the 4 screws threading from the top of the board through the spacers through the bracket and then out the bottom of the bracket The Z6 KEPS nut attaches on the bottom of the bracket Note the bracket has 2 long mounting flanges with a hole SYNTHESIS TECHNOLOGY PAGE 12 MOTM 320 ASSEMBLY 9 12 2011 WWW SYNTHTECH COM in each These attach to the 2 threaded studs sticking out of the rear of the panel The 3 pots each stick in its panel hole when the bracket is screwed down on the 2 threaded posts Attach the pc board to the bracket The flanges will point upwards when the pc board is sitting on the bracket Note that
5. Locate the 10K resistors 11 and solder into R1 above VR2 R13 top amp center of board R17 above C6 R19 right of U2 R21 above R19 R30 beside U3 R38 beside L2 R46 beside C3 R47 right above R58 and R59 both above J8 Locate the 1K resistors 8 and solder into R44 above J5 R52 and R53 both above Q10 R64 above J7 R66 besides R8 R73 above LED SELECT R74 below JP2 and R75 above J6 Locate the 220K resistors 6 and solder into R23 and R24 either side of C5 R32 beside U4 R43 above 44 R78 above VR3 and R79 beside Q12 Locate the 51K resistors 5 and solder into R27 below Q6 R56 beside U6 R68 and R69 above R63 and R77 beside Q12 Locate the 20K resistors 5 and solder into R16 beside VR1 R33 above Q7 R37 beside L2 R60 and R61 below VR3 Locate the 4K7 resistors 4 and solder into R12 beside Q5 R31 below C8 R45 beside Q13 and R51 above R45 Locate the 1M 5 resistors 3 and solder into R22 beside U2 R42 above J3 and R67 beside R8 Locate the 33K resistors 3 and solder into R35 above C8 R39 below Q6 and R63 above C10 Locate the 100K 5 resistors 3 and solder into R20 below J1 R41 above J4 and R57 below VR2 PART 2 BOARD WASH 1 g Verify all the resistors are in the correct position g Verify all the resistors are flat on the board Correct if needed Check solder joints SYNTHESIS TECHNOLOGY PAGE 7 MOTM 320 ASSEMBL
6. OTHER CLEANSERS Most of the parts in the kits are waterproof and can be washed in the sink The flux 15 approved for flushing down the drain so don t worry about that A soft brush 1s used to gently scrub the board We recommend a fingernail brush which is about 1 x 2 and can be found for about 1 The other type of solder is called No Clean Flux because as the name implies it does not require washing This solder is used for wiring the pots switches jacks etc This solder is harder to use on the pc board because even when melted it is not very fluid about the consistency of toothpaste We will use it VERY SPARINGLY on the pc board If you have Internet access there are more pictures and hints on our website at www synthtech com motm OK let s get started on the board PART 1 SOLDERING THE RESISTORS Since there are more resistors than anything else we will start here If you do not know the resistor color code refer to the parts list Resistors are not polarity sensitive but the board will be easier to debug and look nicer if you point the first color band in the same direction for all the parts The color code is also in the README FIRST document that every customer receives with his or her first order You will start by soldering in ALL of the resistors and there is a boatload g Find the RESISTOR bag Set aside the large black 1K Tempco resistor DON T LOSE IT It is soldered at the end
7. Solder the wire in J1 to the SYNC IN jack Insert the panel LED wires through the panel hole from the front The LED has 1 lead longer than the other Solder this to the WHITE wire in J2 and the shorter lead to the ORANGE wire in J2 Be sure the leads do not touch each other Attach the 1 ty wrap around the coax wires and another around the orange white and LED wires Trim off the excess Decide on the jumper setting for the LED You can always change it later The TRI setting will not show effects of the SHAPE setting because the TRI output 13 a constant 5096 duty cycle The other 3 settings will show in different patterns on the LED the output waveform as it goes from positive to negative 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 align the white line to the 0 tick mark and tighten the hex screw The silver part of the knob has a protective clear plastic overlay that can be removed if desired Gently rub with your fingernail across it and it will peel off kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk CONGRATULATIONS YOU HAVE FINISHED BUILDING THE MOTM 320 SYNTHESIS TECHNOLOGY PAGE 14 MOTM 320 ASSEMBLY 9 12 2011 WWW SYNTHTECH COM kkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk All that s left to do is test it But before we do please r
8. function Sweeping the Vbe with a triangle generates a curved triangle that is close to a true sine wave The diff amp Q12 Q13 is biased by temperature compensated constant current source Q10 Q11 The 2 47 ohm resistors R48 and R49 in the emitter leads cause the operating point of the diff amp to shift into the desired region The key to getting the correct output is the Vbe voltage across R55 Normally resistor R77 with R55 sets the Vbe range of Q12 But what we do is feed in a DC offset voltage via R79 into the base of Q12 This will warp the sine wave to bow more upwards or downwards see the scope printouts in the USE OF THE 320 section The differential output is fed into diff amp U3B to form the output waveform The PULSE output is easily done op amp U6B is a comparator that is fed the SAW output from the LFO core and of the SHAPE voltage via divider R68 R69 This generates a variable width pulse out of U6B The large swing about 13 is divided by R70 R71 to a 5V level SYNTHESIS TECHNOLOGY PAGE 16 MOTM 320 ASSEMBLY 9 12 2011 WWW SYNTHTECH COM The output circuitry is the most complicated Working our way from output to input the original sawtooth is deglitched by the slew limiter U8 C10 U5A This circuitry is essentially a linear lag circuit that smoothes the RAMP output and gets rid of the glitch we want to get rid of it because if you were to feed it into a VCO th
9. joints Any solder shorts Too much solder Missing joints g Wash the board under warm water Scrub gently Dry THIS IS A GOOD STOPPING PLACE TO REST OR PUT THE KIT AWAY UNTIL LATER You are now finished with the Organic flux solder All soldering past this point is using the No Clean solder You do not have to wash the board anymore PART 9 FINISHING THE PCB You will now solder in the remaining parts on the pcb in preparation for wiring to the front panel USE THE NO CLEAN SOLDER BE CAREFUL g Locate the Spectrol 149 pots 3 These solder into VR1 VR2 and VR3 It is important that the pots side absolutely flat on the pc board with the shafts sticking straight out over the edge of the board g Locate the 4 pieces of RG 174 black coax cable Note that one end has longer wires stripped than the other The short ends will go in the pc board in locations J5 J6 J7 and J8 Look at the pc board Notice that in the coax positions there is a large hole pad lower pad and a smaller pad top hole The braided wire is soldered into the larger hole The smaller inner conductor goes in the top hole BE SURE THE SHORTER BRAIDED END GOES INTO THE PC BOARD The 1 LONG coax cable solders into J5 The 3 SHORT coax cables go into J6 J7 and J8 Solder each coax cable into the holes Attach a tie wrap to secure the coax cable flush to the board The tie wrap goes down into the left hole and up through the right hole Secure and trim off any exc
10. notches are down g The braided wire on the coax goes to the beveled side of the jacks All of the orange wires go to ground on the jacks beveled side All of the white wires go to the left signal lug g The parts are in the right places and all the transistors face to the right flat side facing the front panel Make sure you didn t swap the transistors around with each other g No solder shorts or missing joints 0 If you have a scope set the RATE control to 10 and check for a triangle wave at pin 9 of U4 a sawtooth at pin 1 of U3 and a square wave at pin 8 of U4 If these are not present check the circuitry around U4 for errors in stuffing SYNTHESIS TECHNOLOGY PAGE 17 MOTM 320 ASSEMBLY 9 12 2011 WWW SYNTHTECH COM EFFECTS OF SHAPE VOLTAGE The following scope shots show the SINE and SAW outputs as the SHAPE pot is rotated from 0 to 10 The pictures appear jaggie due to the 8 bit sample resolution of the scope Tek 100 5 5 70 Acqs Run 100 5 5 Sample 7 2V M500gus Chl 7 40 i 2 Dec 1999 Chi 2 2V M500us Chi 7 40 16 16 58 2 Dec 1999 16 19 27 Tek 100 5 5 469 Acqs Tek 100 5 5 318 Acqs Chi 0450646 ChT ao TREE 2 Dec 1999 Chi 2 2V M500us Chi 7 40 16 21 21 2 Dec 1999 16 23 04 Tek ERE 100 5 5 148 Acqs
11. of construction g Find the MOTM 320 blank pc board There is a copy larger than actual size of the silkscreen which shows where the parts go at the end of this document It will be useful if you locate the part on the print first put the part in the board then check off the silkscreen All parts are inserted from the side of the board with the white silkscreen the top side NOTE some reference designators are under the resistor Be careful g We will stuff the resistors by value to make things easier The resistors and other long leaded parts are inserted on a 0 4 inch spacing The important thing is to be sure that the part is sitting all the way down on the board Push the leads in the SYNTHESIS TECHNOLOGY PAGE 6 MOTM 320 ASSEMBLY 9 12 2011 WWW SYNTHTECH COM holes push the part on the board and then bend the leads on the bottom outwards to 45 degree angle roughly This is called cinching the leads and keeps the part from falling out From the bottom of the board solder using the organic flux applying heat to the pad for about a half second first then applying just enough solder to make a small puddle that looks like a tiny pyramid Enough solder should flow in the hole such that on the top component side a small amount is on the top pad as well The rule of soldering don t use too much you can always add more Cut the leads flush with the top of the solder joint with your diagonal cutters
12. violet orange R14 6 8 blue gray red R15 lea 150K brown green yellow R18 5 green brown red R25 510K green brown yellow R26 lea 3K6 orange blue red R28 1K8 brown gray red R29 lea 39K orange white orange R34 300K orange black yellow R40 lea 2K7 red violet red R71 5ea 100K 1 brown black black orange R2 R3 R7 R80 2ea 243 1 red yellow orange orange R5 R6 lea 54 9 196 green yellow gray red R9 lea 1M 196 brown black black yellow R10 lea 412K 1 yellow brown red orange R65 lea 1 1 3W TEMPCO R8 SYNTHESIS TECHNOLOGY PAGE 2 MOTM 320 ASSEMBLY 9 12 2011 WWW SYNTHTECH COM IC bag containing the following 23 parts TLO74ACN quad op amp U1 1 LM393N dual comparator U2 TLO72 dual op amp U6 U7 NE5517 dual U4 lea OP275GP dual op amp U5 lea CA3080A E OTA U8 5ea BC560C PNP transistor BC550C NPN transistor Q2 Q3 Q7 Q8 Q14 Q1 Q4 Q5 Q10 Q13 2ea BF245A JFET Q6 Q9 4ea 1N4148 signal diodes D1 D2 D3 D4 g Misc 1 bag containing the following 4 parts 2ea Axial ferrite beads plain gray things L1 L2 lea MTA 156 power connector JP1 for LED SELECT mounted on panel lea 4x2 header strip w shunt lea bi color LED SSI LXH 387HGW Knobs 3ea ALCO PKES90B1 4 Jacks 8ea Switchcraft 112A g Pots 3ea containing the following 3ea 100K linear po
13. M 320 ASSEMBLY 9 12 2011 WWW SYNTHTECH COM TV to 0 002Hz to 1400Hz typical 1000 ohms nom to 5V 5 2 8V min sets LFO initial frequency reversing attenuator from 1 to 1 gain range sets the initial duty cycle of all the outputs 15VDC 43 ma nominal 15VDC 44 ma nominal 2U x 5U 34T x 8 12 88 1mm x 221 5mm 4 375 inches 111mm PAGE 20 esus essr 77 9409551 15354 v 25 OZEN 2 ame zoqunm auounsoa ezts T dWTIONINOO HOVIHOA OZE es otara 1 1 668 587 278 LTA AST AST OST9L XL LAOA aes 4299 AE moze dossoa 264 XOOTONHDSL SISHHINAS E x f Leu ANIT 0950 so A 28 axs T m Sta E ast 1 6 to Lo AST z 1 y aS ammi NI 2 8 ast eT sav m 2 com 5 ei znama xo ST T THINOI
14. ND Sl 30B RR Im BER 1 OF 0 22 2 X m V A34 6661 1435 O41 A90 1ONHO93L SISSHLNAS G 5517 IE 2 50 E R34 8800 CO 3080 1072 c NS ENG my amp mm 125 2
15. Y 9 12 2011 WWW SYNTHTECH COM Wash the board in warm water gently scrubbing both sides DO NOT USE ANY SOAP Just water 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 Take a little break You are about 1 of the way finished stuffing resistors PART 3 RESISTOR STUFFING 2 auuguuauga g u ui cutuiu Locate the 62K resistors 2 and solder into R36 beside L2 and R62 beside U5 Locate the 47 ohm resistors 2 and solder into R48 and R49 below Q11 Locate the 2K resistors 2 and solder into R50 beside Q13 and R55 beside Q12 Locate the 13K resistors 2 and solder into R54 below L1 and R76 beside C12 Locate the 1K3 resistors 2 and solder into R70 above 48 and R72 below JP2 Locate the 7K5 resistor and solder into R11 above Q9 Locate the 27K resistor and solder into R14 beside Q4 Locate the 6K8 resistor and solder into R15 beside Locate the 150K resistor and solder into R18 beside D4 Locate the 5K1 resistor and solder into R25 above J6 Locate the 510K resistor and solder into R26 beside U2 Locate the 3K6 resistor and solder into R28 left U7 Locate the 1K8 resistor and solder into R29 above R28 PART 4 BOARD WASH 2 Verify all the resistors are in the correct position SYNTHESIS TECHNOLOGY PAGE 8 MOTM 320 ASSEMBLY 9 12 2011 WWW SYNTHTECH COM 0 o Verify all the res
16. at side shown on the silkscreen Place the transistor in the holes but do NOT press the transistor all the way to the pc board Leave about 0 1 inch of the leads exposed between the pc board and the underside of the transistor Solder into Q1 Q4 Q5 Q10 Q11 Q12 and Q13 Locate the BC560C transistors 5 Solder into Q2 Q3 Q7 Q8 and Q14 Locate the BF245A JFETS 2 and solder into Q6 and Q9 Locate the MTA 156 power connector Solder into JP1 Note that the connector has a locking tab on one side This side is the inside facing relative to the pc board Note the silkscreen symbol for JP1 has a line on one side indicating this 1s the side where the locking tab goes SYNTHESIS TECHNOLOGY PAGE 10 MOTM 320 ASSEMBLY 9 12 2011 WWW SYNTHTECH COM g In the JP2 position solder an orange white wire Now the silkscreen will say RED and BLACK this was from the original LED that is no longer available Solder the WHITE into RED and the ORANGE into BLACK The holes are also a bit large be sure to fill them with solder g Apply a small bit of solder to the via holes These are the small pads that allow traces to change sides of the pc board DO NOT SOLDER PADS FOR THE REMAINING COMPONENTS PART 8 FINAL BOARD WASH amp INSPECTION g Verify all the parts are in the correct locations Make sure all of the ICs are pointing the same direction Make sure all of the transistors are facing the same direction g Inspect the solder
17. e hiccup in output frequency of the modulated VCO would be audible The circuitry around U6A and Q14 form a DC summer rectifier The LFO sawtooth voltage is added to the SHAPE voltage by U6A with a fixed offset set by R56 R65 of 1 85V The emitter of Q14 is at 7 5 Based on the total output voltage of U6A Q14 turns off and on This generates the RAMP waveform as shown in the scope shots The panel LED is driven by amp U5B which acts as a switch The selected waveform via jumper block LED SELECT is fed into U5B which at first looks like a buffer What happens is that for positive waveform cycles current flows through 1 LED and then is steered to ground by D4 R73 sets the brightness level For negative cycles D4 is reversed biased off and current flow out of the op amp through the panel LED and then through R72 which of course sets the LED brightness LED SELECT allows different visual indications of the waveforms Note that jumpering TRI will not show any SHAPE effects as the TRI output is a fixed duty cycle 50 Note that you can t make the panel LED really bright due to the available current provided by UBB TROUBLESHOOTING If your MOTM 320 does not work please verify ALL of the following before contacting us The following reference directions assume that you are looking at the pc board with the panel to the right and the power connector to the left g All of the ICs are pointing the same way and all
18. ead the following Theory of Operation THEORY OF OPERATION The MOTM 320 uses a discrete approach to a LFO design Instead of the cheesy and simple Tri Square LFOs found on most synths the MOTM 320 has full waveshaping that is voltage controlled Also very careful design and component selection allows the MOTM 320 to cover a very wide range of frequencies from 1 cycle in 20 minutes 0008Hz to about 1200Hz That s a span of over 20 octaves And to top it off the MOTM 320 has full temperature compensation the first in any dedicated LFO LFO CORE Page 1 of the Schematic The heart of the LFO is a triangle built by charging discharging capacitor C8 Since we are concerned with running at low frequencies the physical properties of C8 are critical to LFO operation It may not look special on the outside but inside the cap is wound with a film material called PPS polyphenylene sulfide PPS film 13 used for 2 reasons in this application a extremely temperature stable from 40 to 180 not that we even see that range b very low leakage currents for operating at very low frequencies The bad new is that PPS is not so great at higher frequencies say 5Khz and above but this is a LFO not a musical VCO although certain users will attempt to use it as such The is controlled by an U4B and is buffered by FET Q9 FET is again for operating at very low frequency as it keeps current fr
19. ess SYNTHESIS TECHNOLOGY PAGE 11 MOTM 320 ASSEMBLY 9 12 2011 WWW SYNTHTECH COM Find the 4 orange white twisted wires These go into locations J1 42 J3 and J4 In all cases the WHITE wire goes into the 1 hole and the ORANGE wire goes in the 2 hole Note carefully the wire is stripped with one long end and one short end Be sure the short end goes into the pc board Solder the 2x4 header strip into the LED SELECT location The short ends go into the pc board Don t lose the blue jumper Find the 1K Tempco resistor This solders into R8 and must also be so that it touches both Q1 and Q2 Bend the leads and put the resistor in but about 1 inch off the board Now apply a tiny bit of heat sink compound to the flat sides of Q1 and Q2 Then gently press the Tempco flat on the pc board with the 2 transistors contacting the body of R8 You may need to slightly bend the transistors forward to touch R8 Solder R8 in position all the way flat on the pc board surface YOU ARE NOW FINISHED WITH THE PC BOARD WORK BREAK TIME PART 7 FRONT PANEL PREPARATION You will now attach components to the front panel It is HIGHLY recommended that you use a set of hollow shaft nut drivers NOT PLIERS to tighten the nuts This prevents scratching NOTE all references to part orientation 1s from the REAR of the panel Locate the 8 Switchcraft Jacks Notice that from the rear there 15 a beveled corner This corner is ALWAYS CONNECTED TO
20. he panel Again make sure each pot s nut is touching the back of the panel no gaps There will be a gap from the edge of the pc board to the panel Remove the hex nuts amp For all of the pots first put on the flat washer then the hex nut Tighten with nut driver PART 9 FINISH WIRING TO THE PANEL Please read the following instructions carefully In order to neatly attach the many wires to the front panel components the wires are soldered in a specific order SYNTHESIS TECHNOLOGY PAGE 13 MOTM 320 ASSEMBLY 9 12 2011 WWW SYNTHTECH COM UUUd Now you will solder to the 8 jacks Each jack has 3 lugs from the rear we will refer to them as LEFT TOP and BEVELED The TOP lug is for the switched contact this is a NC normally closed contact that 1s opened when a plug in inserted In all cases this lug 1s left unconnected IN ALL CASES the coax braid goes to the beveled lug and the inner wire to the right lug Solder the coax in J8 to the PULSE jack Route the coax in between the SHAPE and PULSE jacks Solder the braid to the BEVELED lug and the inner wire to the LEFT lug Solder the wire in J4 to the SHAPE jack Orange wire to BEVELED white wire to LEFT This connection is the same for J1 J4 Solder the coax in J7 to SAW jack Solder the wire in J3 to the FM jack Solder the coax in J6 to the TRI Jack Solder the wire in J2 to the 1V OCT jack Solder the coax in J5 to the SINE jack
21. istors are flat on the board Correct if needed Check solder joints Wash the board in warm water gently scrubbing both sides DO NOT USE ANY SOAP Just water Shake the board a couple of times blot dry Take a little break You are about 3 4ths of the way finished stuffing resistors PART 5 RESISTOR STUFFING 3 OU U Q UU Locate the 39K resistor and solder into R34 above Q7 Locate the 300K resistor and solder into R40 left of U1 Locate the 2K7 resistor and solder into R71 above J8 Locate the 100K 1 resistors 5 and solder into R2 and R3 above VR2 R4 R7 and R80 left of U1 Locate the 243K 1 resistors 2 and solder into R5 and R6 left of U1 Locate the 54K9 1 resistor and solder into R9 below J4 Locate the 1M 196 resistor and solder into R10 below 44 Locate the 412K 1 resistor and solder into R65 below VR2 PART 6 CAPACITORS amp board wash o o 0 o Locate CAPACITOR bag Locate the 0 01mfd PPS film cap and solder into C8 Locate the 1000pf 1nf yellow box caps 2 and solder into C5 and C10 Locate the 0 1 mfd axial caps and solder into C4 C6 C7 C9 C11 and C12 Locate the 10 electrolytics 2 Note that there is a stripe on the NEGATIVE terminal The pc board has a on the POSITIVE terminal Carefully stick the capacitors into C1 and C2 with the stripe away from pad on the board Wash the board again gently scrubbing both sides
22. om leaking back into the buffer stage pin 10 of U4B The frequency of the LFO 1s controlled by the current flowing into pin 16 labeled ICNTRL set by exponential converter Q1 Q2 This configuration is different from others in that it uses a NPN PNP pair These are discrete TO 92 transistors which are in physical contact with Tempco temperature compensating resistor R8 The reference current the current applied to the OTA with control voltage set to zero 1s set by 1M resistor R10 Scaling to nearly 1V Oct is by the divider ratio R9 R8 The input summing network is straightforward U1A B form a reversing attenuator for the FM IN jack The LFO s initial rate 1s set by panel pot VR1 U1C sums all the control voltages together To get the triangle wave we switch U4B from source to sink with a discrete Schmitt trigger Q3 Q4 Q5 This 15 a diff amp with one side set as a latch Q3 The trip point is the R13 R16 ratio or at 5 The output signal called BUFIN because it is buffered by U4A is a square wave at the triangle wave s frequency The square wave does two things it SYNTHESIS TECHNOLOGY PAGE 15 MOTM 320 ASSEMBLY 9 12 2011 WWW SYNTHTECH COM reverses the output of the triangle and it drives the tri to saw converter U4A The saw converter is a crude but effective slope changer when the triangle reverses slope square wave then reverses the slope at the SAW output This forms a saw from the triangle but the
23. re will be a glitch in the middle of the transition due to finite switching speeds of the and current source Q7 Q8 Later on this sawtooth is deglitched Op amp U1D is a simple summing amp for the voltage controlled waveshaper The initial shape is set by panel pot VR3 Modulating voltages at SHAPE IN jack are added subtracted from the pot setting The 320 can by sync d to an external oscillator The sync waveform at SYNC IN jack is compared to a trigger threshold set by R18 R19 about 1V The SYNC waveform can be any zero crossing waveform greater than 3V pk pk The output of comparator U2A is 15V squared version of the input This is passed through a pulse shaping network C5 R23 and D1 to generate a narrow trigger pulse into U2B This then shorts FET Q6 which causes C8 to be yanked to the 15V supply Generally speaking the frequency of the wave at SYNC should be lower than the LFO frequency If you try to sync to a higher frequency the output of the LFO becomes distorted Some users will find this amusing and to their advantage WAVESHAPING SECTION Page 2 of the Schematic There are 3 separate waveshapers all driven in parallel by the LFO core Each one is discussed in detail below The SINE shaper uses the Moog modular degenerative emitter circuit This circuit uses a little known fact that you can bias a differential amplifier to a certain point on the Ic Vbe curve to approximate a sine
24. rs Diagonal cutters Allen key set for securing the knobs 1 16 or 1 6mm Magnifying glass to read the capacitor codes and to inspect solder joints Lead bending tool optional but makes the job go much faster DVM Digital Volt Meter or oscilloscope to check the output 1 Philips screwdriver Fingernail brush for washing off the organic flux Old towel for blotting dry pc board Small amount of silicone heat sink compound For more information of tools used and suggestions see the MOTM FAQ and Tutorial pages at http www synthtech com HOW TO FOLLOW THE DIRECTIONS Please read the entire instruction before proceeding There may be valuable information at the end of the instruction Each instruction has a check box next to it After you complete the instruction check the box This way you can keep track of where you are in the process VERIFY THE PARTS LIST g Verify that all of the parts are in the kit as shown on the parts list SYNTHESIS TECHNOLOGY PAGE 5 MOTM 320 ASSEMBLY 9 12 2011 WWW SYNTHTECH COM WORD ON SOLDERING There are 2 very different types of solder used in the kit Most of the soldering uses Organic Flux solder This is strictly for use on the pc board and is NOT to be used on the front panel wiring In order for solder to stick to the copper a chemical called flux is embedded in the solder The flux leaves a residue on the pc board that should be cleaned with warm water DO NOT USE SOAP OR
25. synthesis technology MOTM 320 Voltage Controlled LFO Assembly Instructions amp Owner s Manual Synthesis Technology 6000 Highland Hills Lane Fort Worth TX 76034 www synthtech com Sept 12 2011 MOTM 320 PARTS LIST Please carefully check that all parts are in your kit If you have a suspected shortage please call or email If you get free extra stuff keep it for next time g Capacitor bag containing the following 12 parts 2ea 10mfd Electrolytic 16V or 50V C1 C2 lea 0 01mfd film cap reddish brown C8 2ea 1000pf yellow box marked 1N or 102 C5 C10 0 1mfd marked 104 ceramic axial C3 C4 C6 C7 C9 C11 C12 g Resistor bag containing the following 80 parts 11ea 10K brown black orange R1 R18 R17 R19 R21 R30 R38 R46 R47 R58 R59 8ea 1K brown black red R44 R52 R53 R64 R66 R73 75 6ea 220K red red yellow R23 R24 R32 R43 R78 R79 5ea 51K green brown orange R27 R56 R68 R69 R77 5ea 20K red black orange R16 R33 R37 R60 R61 4ea 4K7 yellow violet red R12 R31 R45 R51 1M brown black green R22 R42 R67 33K orange orange orange R35 R39 R63 3ea 100K brown black yellow R20 R41 R57 2ea 62K blue red orange R36 R62 2ea 47 ohms yellow violet black R49 2ea 2K red black red R50 R55 2ea 13K brown orange orange R54 R76 2ea 1K3 brown orange red R70 R72 lea 7K5 violet green red R11 lea 27K red
26. the bracket holes for the pc board are actually oblong This is to allow adjustment for the pc board to firmly press up against the back of the panel As a start set the 4 screws ALL THE WAY TO THE LEFT of the oblong holes Loosely tighten the 4 KEPS nuts on the bottom THIS IS A VERY IMPORTANT STEP SO PAY ATTENTION AND READ ALL OF IT BEFORE PROCEEDING Note that each of the 3 pots on the pc board have 2 hex nuts and a flat washer Remove the first hex nut and the washer Set aside What you will do now is adjust the remaining hex nuts so that when the bracket 1s all the way down on the panel s threaded studs all the pot hex nuts touch the rear of the panel Screw by hand each hex nut on the pots so that it is all the way on touching the face of the pot Now pick up the pc board bracket assembly and carefully slide it over the 2 threaded studs making sure the pots are aligned in the holes Use 2 6 KEPS nuts and tighten the bracket to the panel Loosen the 4 KEPS nuts on the bottom of the bracket Slide the pcb ALL THE WAY TO THE RIGHT AS FAR AS IT WILL GO so that the 3 pot nuts are all pressing against the panel By hand put hex nuts on the outside threads of VR1 and VR3 to keep the board place Now tighten the 4 KEPS nuts on the bracket pcb and bracket should be secure with no gaps visible between the panel and the pot nuts You may need to loosen the nuts on the pots so that they are touching the back of t
27. ts VR1 VR3 g Front panel Mounting bracket g Wire bag containing the following 9 wires 3ea RG 174 coax 4 inches lea RG 174 coax 7 inches 5ea 2 wire set 22ga 6 5 inches white orange lea Power Cable 20 SYNTHESIS TECHNOLOGY PAGE 3 MOTM 320 ASSEMBLY 9 12 2011 WWW SYNTHTECH COM g Hardware bag containing 4ea 8 32 x 3 8 black screws for mounting module to rack 4ea 6 32 x 1 2 zinc screws for attaching pc board to bracket 4ea 1 4 inch aluminum spacers 6 KEPS nuts 2 for attaching bracket to front panel 4 for board small tie wraps Organic Solder No clean Solder PC Board MOTM 320 SYNTHESIS TECHNOLOGY PAGE 4 MOTM 320 ASSEMBLY 9 12 2011 WWW SYNTHTECH COM GENERAL INFORMATION Thank you for purchasing the MOTM 320 Voltage Controlled LFO Low Frequency Oscillator If you have any issues concerning the building or use of the kit please contact us by email syntht yahoo com This kit should take the average builder between 4 and 5 hours The LFO kit contains many different resistors and special parts However please remember this is NOT a speed contest it is an accuracy contest There 18 no rule that you have to complete the entire kit in one day as long as you wash the flux off Successful kit building relies on having the proper tools Here is a list of what you will need to build your 320 Soldering iron 50W max power Needle nose or chain nose plie
28. ying sync pulses at a faster rate than the triangle oscillator is running will cause severe distortion of the output waveform MODIFICATIONS The following FAQ is a list of possible modifications to suit user taste Note that Synthesis Technology does not offer the parts needed Good sources of parts for modifications are Mouser Electronics www mouser com and Digikey www digikey com Q1 How can I speed up slow down the LFO A Change capacitor C8 A larger value say 0 022mfd will make the total overall range scale accordingly A smaller cap say 0 0047mfd will speed up the overall rate Note that too large of a cap may cause erratic performance at the lowest RATE settings The suggested cap is a PPS film from Digikey the Panasonic ECHS series polystyrene cap can be used but they tend to be larger in physical size Q2 How do I increase the LED brightness A Not much you can do The LED is on the dim side because of the current limit set by the op amp Also excessive LED brightness can easily double current consumption of the module You can lower R72 and R73 slightly SYNTHESIS TECHNOLOGY PAGE 19 MOTM 320 ASSEMBLY 9 12 2011 WWW SYNTHTECH COM SPECIFICATIONS MOTM 320 Voltage Controlled LFO Control Voltage input levels Frequency range Output impedance Output amplitude SYNC input level CONTROLS RATE FM SHAPE GENERAL Power Supply Size Depth behind panel SYNTHESIS TECHNOLOGY MOT
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