SYNTH SYSTEMS JLH 822 Assembly instructions Revision 1: 02/05/02 The JLH-822 Step and Octave voltage switch has an option to consider before beginning construction. This option must be determined as component selection and placement will be impacted. This option concerns the 1-volt-per-octave DC accuracy of the 822. There are two methods to achieve this accuracy. You must select one or the other prior to construction as component placement varies Method # 1 involves carefully hand-matching some critical resistors in the circuit. If you use this method, there is no need to install the 1-volt-octave trimmers. I believe this method is the best alternative for building the 822. However, be aware that VERY close matching is essential. I recommend that the 10K resistors be matched within 0.3 ohms and the 100K resistors be matched within 3 ohms. You need at least a 5 1/2 digit digital meter to accomplish that level of matching accuracy. Method # 2 Allows a 1-volt-per-octave trimmer to be installed in series with the input resistor so that the gain of the 1-volt-per-octave DC control voltage can be controlled in the first op-amp stage. This single trimmer can offset any error in the entire 822 circuit path for the 1-volt per-octave control voltage. While this method might seem the best option, trimmers are not as stable as fixed resistors. Lets examine method #1- matching resistors first. If you choose this method, here are the resistors that must be matched: * 100K - R21 must be exactly matched to 100K - R22 * 100K - R27 must be exactly matched to 100K - R28 * 10K - R33 must be exactly matched to 10K - R34 * 10K - R36 must be exactly matched to 10K - R37 None of the other resistor values are critical in the circuit. However, I generally recommend 1% resistors for many locations as indicated in the parts list. Important: If you use the hand match method # 1 for construction of your 822 you must install resistors R21, and R27 in the "B" positions on the circuit board. These are the positions that cover the trimmer install locations. The unused trimmer holes will be covered by these resistors. Nothing is installed in the "A" positions for R21, and R27. Now, let's take a look at method # 2 which involves adding 2 more trimmers to the circuit. (If you plan to use hand matched resistors, just skip this part - to the point marked - end of skip --) Measurement of resistors is still important in this construction method. However, the exact accuracy is not required. In fact, if you are not having success with the tracking of your hand matched circuit, I recommend adding trimmers to the circuit. In method # 2, some resistors should still be selected as close matches. Resistors should be selected as follows. * 100K - R21 must be less than 100K - R22 * 100K - R27 must be less than 100K - R28 The concept is that R21 + trimmer setting value (about 1/2 of trimmer range) must = R22. The same is true for the R27 to R28 relationship. R27 has the lesser value. Therefore, if you selected a value or R21 that was about 200-300 ohms less than R22, you could use a 500 ohm trimmer. The 500 ohm trimmer should trim out somewhere near mid-range. * 10K - R33 should be closely matched to 10K - R34 * 10K - R36 should be closely matched to 10K - R37 You need to get these as close as reasonable. The closer they are, the less adjustment is needed in the new trimmers in the input stage buffer / summer. Whether you choose method # 1 or # 2, trimming the effect of the interval switch to be consistent across the channels remains identical. Therefore, just as in method # 1, the following describes selecting R24, R25, R30, and R31. * 402K - R24 and 402K - R25 should be close in value to each other. An exact match is not important. Within 500 ohms is recommended. * 392K - R30 and R31 - These were changed to 392K so that more trimmer range is available at VR18 and VR 19 which were changed to 20K trimmers. Important: If you use the trimming method # 2 for construction of your 822 you must install resistors R21 and R27 in the "A" positions on the circuit board. These are the positions that do NOT cover the trimmer install locations. The "B" positions are now used for the trimmer installations. Notice that the "4th" hole in the "B" position unused by the trimmer has no connection. ----------------- end of skip ------------------ Now, that you have your construction method and component selection out of the way, let's gets started building. You will start by installing the resistors. In these details, I will assume you are using the hand matched method #1, please make appropriate adjustments as detailed above if you have elected to trim your 1-volt-per-octave voltage using method # 2. First, a word about solder. After assembly of quite a few MOTM kits, Paul Schreiber has convinced me that the effort needed to use two different types of solder is well worth while. I always assemble my PCBs now with a washable solder. In fact, I use the same Kester 331 organic solder that Paul supplies with his kits. The instructions for the 822 assembly are written assuming that assembly strategy. PART 1: Installing the resistors and ferrite beads We will use organic washable solder for this part of the construction. * Install a 100K patched pair at R21B and R22 (note R21A remains unused). * Install a 100K patched pair at R27B and R28 (note R27A remains unused). * Install 10K matched pair at R33 and R34 * Install 10K matched pair at R36 and R37 * Install 402K, 1% resistors (two) at R24 and R25. * Install 392K, 1% resistors (two) at R30 and R31. * Install 24K, 1% resistors (two) at R26, and R32 * Install 5K1, 1% resistors (two) at R35, and R38 * Install 51K, 1% resistors (two) at R42, and R44 * Install 180K, 5% resistors (two) at R23, and R29 * Install 100K, 5% resistors (two) at R39, and R40 * Install 470 ohm, 5% resistors (two) at R41, and R43. * Install 59 ohm, 1% resistor at R1 * Install 33 ohm 1% resistors (ten) at R2, R3, R4, R5, R6, R7, R8, R9, R10 and R11. * Install 2.8K ohm, 1% resistor at R12 (PCB is marked 14K, ignore that) Note: On some 822s I have found that a 2.74K ohm is needed here due to part tolerances. If you cannot get the +10 or, +10 and +11 steps to calibrate, try the 2.74K ohm. * Install 698 ohm, 1% resistors (two) at R13 & R20 (PCB is marked 12 K, ignore) * Install 887 ohm, 1% resistors (two) at R14 and R19 * Install 909 ohm, 1% resistors (two) at R15 and R18 * Install 953 ohm, 1% resistors (two) at R16 and R17 This completes the installation of all the resistors on your 822 PCB. Before the board wash, let's install two more components. * Install the two ferrite beads at FB1 and FB2 (read important note first). Important: Unlike resistors and most other components, the ferrite beads are not insulated on the outside. Because there is no solder mask on this PCB, we must be certain that the ferrite beads do not cause any shorts on the PCBs under their mounting location. The PCB ground plane does run right under these components. Therefore, we must add some insulation to the ferrite beads before we install them. I cut lengths of heat shrink just a little longer than the bead itself, slid them over the bead and shrank them. This applied a very nice insulation to the entire bead. There are no via holes on this PCB that need to be soldered. OK, this is a good stopping point for our first board wash. Run the board under warm water (do not use any soap or cleaners). Gently scrub both sides of the board to remove the organic flux. Any small brush will do the job. I use an old toothbrush. If you have not done so already, this would be a good point to inspect your solder joints. Check to be certain you have not forgotten to solder one end of a component or that you have not accidentally bridged one thing to another with excess solder. Personally, I check my joints right before I clip my leads. It seems easier to me to find what I have just competed that way. PART 2: Installing the remaining components on the PCB When assembling, my preference is to install components by relative height. For example, I find it much easier to install integrated circuits if other taller components have not already been installed. That method is suggested here. However, skip around as you desire. It really does not matter much what order the components are installed in this part. * Install (six) 0.1uF ceramic capacitors at C3, C4, C5, C6, C7, and C8. These small ceramic capacitors are marked 104. These are located at both ends of each of the three integrated circuit positions. They have no polarity. * Install (three) LT1013 integrated circuits (dual op amps) at U1, U2, and U3. Be certain to insert them in the proper direction. The notch or dot marking pin 1 should face toward the end of the PCB with the ferrite beads. Notice the marking also on the circuit board. All three I.C.s face the same direction. * Install (four) yellow box capacitors at C9, C10, C11, and C12. The marking on the capacitors will be either 1n0 or 102. These capacitors have no polarity. * Install (two) 10uF electrolytic capacitors at C1 and C2. Notice the NEGATIVE stripe on one side of the capacitor. The PCB has a (+) sign on the POSITIVE terminal. Install the capacitor with the stripe away from the (+) pad. Also notice the capacitor lead that goes to the (+) pad is usually longer than the other. The size of these capacitors is not critical. Anything between 10uF and 50uF is fine. * Install (eleven) 50 ohm trim pots at VR1, VR2, VR3, VR4, VR5, VR6, VR7, VR8, VR9, VR10, and VR11. You will notice the part will install in either direction. It does not matter. They look better if you install them all in the same direction. I placed mine so that the adjustment screw is toward the back of the PCB. I thought that might make calibration easier. * Install (six) 100 ohm trim pots at VR12, VR13, VR14, VR15, VR16, and VR17. You will notice the part will install in either direction. Again, it does not matter. I placed mine so that the adjustment screw is toward the back of the PCB. I thought that might make calibration easier. * Install (two) 20K ohm trim pots at VR18, and VR19. You will notice the part will install in either direction. Again, it does not matter. I placed mine so that the adjustment screw is toward the back of the PCB. * Install the MTA power connector. Notice that the connector has a locking tab on one side. The part is installed with this side facing inside on the PCB. The PCB silkscreen symbol has a line on one side indicating the position of the locking tab. OK, this is a good stopping point for another board wash. Run the board under warm water (do not use any soap or cleaners). Gently scrub both sides of the board to remove the organic flux. This is our last board wash. We will NOT use washable solder for the remainder of construction. If you have not done so already, this would be a good point to inspect your solder joints. Check to be certain you have not forgotten to solder one end of a component or that you have not accidentally bridged one thing to another with excess solder. PART 3: Attaching connecting wires to the PCB The 822 Step and Octave voltage switch must be connected with flexible insulated wire to four front panel switches and four 1/4" phone jacks. No shielded coax cable is required. All of the soldering from this point forward will use no-clean solder. For the remainder of this construction, do NOT use washable solder and do NOT wash the board. * Cut 8 pieces of wire in lengths appropriate to reach from the 831 PCB to your front panel jacks. I suggest using 4 lengths each of two different colors to prevent the possibility of error when connecting to the front panel jacks. For the sake of instruction, I have selected red and black. * Solder the 4 lengths of red wire to each of the ROUND pad holes furthest from the bottom edge of the PCB for IN A, IN B, OUT A, and OUT B. * Solder the 4 lengths of black wire to each of the SQUARE pad holes closest to the bottom edge of the PCB for IN A, IN B, OUT A, and OUT B. * Twist each of the red and black pairs of wire together. * Cut 38 pieces of wire in lengths appropriate to reach from the 822 PCB to your front panel switches. I suggest using 4 lengths of one color and 34 lengths of a different color to prevent the possibility of error when connecting to the front panel switches. For the sake of instruction, I have selected green and white. I learned after constructing my very first voltage switch that you will thank yourself if you strip the wire on both ends and tin the ends before attaching to the PCB. This will make attachment to the rotary switches MUCH easier. It is difficult to strip back the wires for attachment to the rotary switches after they are attached to the PCB. Cut each of the wire jumpers 2 inches long. * Solder the 4 lengths of white wire to the A, B, C, and D pads on the right edge of the PCB. * Solder 11 lengths of the green wire to the +1, +2, +3, +4, +5, +6, +7, +8, +9, +10, and +11 pads at the right edge of the PCB at the "A" switch location. * Solder 6 lengths of the green wire to the -3, -2, -1, +1, +2, and +3, pads at the right edge of the PCB at the "C" switch location. * Solder 11 lengths of the green wire to the +1, +2, +3, +4, +5, +6, +7, +8, +9, +10, and +11 pads at the right edge of the PCB at the "B" switch location. * Solder 6 lengths of the green wire to the -3, -2, -1, +1, +2, and +3, pads at the right edge of the PCB at the "D" switch location. This is another good spot to take a break Soldering all of these wires to the rotary switches will be the most difficult part of assembling your 822. You should be fresh before you continue. Part 4: Preparing the front panel and switches Before continuing here are some notes on rotary switches. There are two issues with rotary switches for the 822 voltage switch. Please consider these carefully Issue # 1: The 822 module is designed to conform to the MOTM size format standard. However, the MOTM standard was never designed with rotary switches in mind. The standard specified rotary switches for the 822 encroaches slightly into the standard 1/2 inch clearance at the top of the MOTM panel. It leaves only 3/8 inch clearance. That matters not if you use rail mounting. The 822 still fits just fine. But, for anyone considering a wood cabinet and / or flat rails you might have some clearance issues. I have an alternate switch selected with a smaller diameter. The new switch is Electroswitch C6P0112N-A or C5P0012N-A. Either will work. They are commonly available switches. I got them from Allied Issue # 2: The rotary switch uses all 12 positions for the STEP switch. So, it would be nice if the switch supported continuous rotation. The rotary switches are available in full rotation and adjustable stop. You need two of each. The adjustable stop versions are used for the "octave" switches. The continuous rotation switches are better for the "step" switches. * Preparation of the OCTAVE switches is required to set the adjustable stop. Remove the nut and lock-washer. Remove the adjustable stop and reinsert it so that the movable stop goes in the hole marked "7" Obviously, that means the switch will only have 7 positions available. * I like to bend the rotary switch connections that will not be used flat down on to the back of the switch. This gets them out of your way making it a bit easier to solder to the remaining lugs. You could just break or cut them off. But, that seemed too "final" to me. * Install the 4 switchcraft jacks onto the front panel. I always install mine in MOTM fashion with the bevel to the upper right corner. The lock-washer goes on the back. * You should rotate your continuous rotation switches to a certain position before you install them. This will help you when time comes to install the knobs. You could find the position later, but it is easier while the switch is not installed. * Use your ohm meter to determine current position of the two STEP position rotary switches. Set them to any position you choose, but write it down so you don't forget. I recommend position 9. You will see why later. * Install the four rotary switches through the appropriate holes in the mounting bracket. Be sure to put the prepared step switches in holes 1 and 3 and the octave switches 2 and 4. Notice the bracket has a hole that exactly fits the turn-stop on the switch so it will not try and turn behind the panel when operated from the knob. The lock-washer should be installed on the switch shaft BEFORE you insert it in though the bracket. * Align the bracket and switches with the front panel and push the switch shafts through the holes in the front panel. Install the 4 switch nuts and tighten. This holds the panel and bracket together. DO NOT OVERTIGHTEN. These are plastic. They do not have to be very tight as the turn-stop secures the switch from undesired rotation. I recommend using a socket from your ratchet set WITH OUT the ratchet. Hold the socket in your hand and tighten the four switch nuts until they feel snug. No more. The bracket should be pulled up next to the back of the panel. The rotary switch turn-stops should still be nestled into their hole. * Attach the PCB to the bracket with # 6 screws and nuts and spacers. Part 5: Attaching the wires from the PCB to the front panel * Connect the OUT A red and black twisted pair from the PCB to the OUT A jack on the panel. The black wire attaches at the beveled lug. The red wire attaches at the left lug. Nothing is attached to the top lug. * Connect the OUT B red and black twisted pair from the PCB to the OUT B jack on the panel. The black wire attaches at the beveled lug. The red wire attaches at the left lug. Nothing is attached to the top lug. * Connect the IN A red and black twisted pair from the PCB to the IN A jack on the panel. The black wire attaches at the beveled lug. The red wire attaches at the left lug. Also attach a second short wire to the left lug with the red one. The left lug now has two wires. Nothing is attached to the top lug. * Attach the opposite end of this short wire from A IN to the TOP lug of the B IN jack. The B IN jack will be the only jack to have a wire attached to its top lug. * Connect the IN B red and black twisted pair from the PCB to the IN B jack on the panel. The black wire attaches at the beveled lug. The red wire attaches at the left lug. Now , you will connect the wires from the PCB to the rotary switches. * You will start with the wiring from the PCB to switch STEP A. All lugs will be connected on this switch except lug # 12. Push lug 12 over flat on the back of the switch out of your way. You can solder the wires in any order you choose. Wire +1 connects to switch lug 1, wire + 2 to switch lug 2 and so on though wire + 11. However, soldering them in that order is not the best approach. Instead, I recommend soldering the wires to the "lower" lugs closest to the PCB first. Otherwise, you will have one heck of a time getting to these lugs and wires once you have wires running over the top of them. * Start with lugs 6, 7, and 8. These are the most difficult to reach. Once you have those three done, the remainder will be somewhat easier. * Then, work upwards attaching wires on both sides alternating in a fashion that makes sense to you until you have all wires connected. Yes, they do cross. * Don't forget to connect the white "A" wire to the center lug before you connect the wires across the top lugs 1, 2, and 11. * Next, you will connect the Octave A switch. This one is much easier. The following lugs are NOT used: 4, 8, 9, 10, 11, and 12. Bend them over out of your way. * Connect the +3 wire from the PCB to lug # 7 on the A Octave switch. * Connect the +2 wire from the PCB to lug # 6 on the A Octave switch. * Connect the +1 wire from the PCB to lug # 5 on the A Octave switch. * Nothing connects to lug # 4. Be sure you skip over this one. * Connect the white "C" wire to the center lug. * Connect the -1 wire from the PCB to lug # 3 on the A Octave switch. * Connect the -2 wire from the PCB to lug # 2 on the A Octave switch. * Connect the -3 wire from the PCB to lug # 1 on the A Octave switch. * Next you will connect wires from the PCB to switch STEP B. All lugs will be connected on this switch except lug # 12. Push lug 12 over flat on the back of the switch out of your way. You can solder the wires in any order you choose. Wire +1 connects to switch lug 1, wire + 2 to switch lug 2 and so on though wire + 11. However, soldering them in that order is not the best approach. Instead, I recommend soldering the wires to the "lower" lugs closest to the PCB first. Otherwise, you will have one heck of a time getting to these lugs and wires once you have wires running over the top of them. * Start with lugs 6, 7, and 8. These are the most difficult to reach. Once you have those three done, the remainder will be somewhat easier. * Then, work upwards attaching wires on both sides alternating in a fashion that makes sense to you until you have all wires connected. * Don't forget to connect the white "B" wire to the center lug before you connect the wires across the top lugs 1, 2, and 11. * Next, you will connect the Octave B switch. This one is much easier. The following lugs are NOT used: 4, 8, 9, 10, 11, and 12. Bend them over out of your way * Connect the +3 wire from the PCB to lug # 7 on the B Octave switch. * Connect the +2 wire from the PCB to lug # 6 on the B Octave switch. * Connect the +1 wire from the PCB to lug # 5 on the B Octave switch. * Nothing connects to lug # 4. Be sure you skip over this one. * Connect the white "D" wire to the center lug. * Connect the -1 wire from the PCB to lug # 3 on the B Octave switch. * Connect the -2 wire from the PCB to lug # 2 on the B Octave switch. * Connect the -3 wire from the PCB to lug # 1 on the B Octave switch. Finishing your 822 You have probably realized by now that installing the knobs is all that remains. If you followed the instructions before, and set your two STEP rotary switches to the # 9 position, knob installation is simple. Install your knobs so the pointer is toward 9 on the STEP A and STEP B switches. I selected 9 because it is easier to tighten the switches from the sides Rotate these switches to the 12 o'clock positions. For OCTAVE A and OCTAVE B switches, rotate the switches counter-clockwise until they are against the stop and will turn no more. Install your knobs so the pointer is toward -3 on the OCTAVE A and OCTAVE B switches. Rotate these switches to the 12 o'clock or no-shift positions. Congratulations ! You are now complete with your 822 construction. Take a moment to inspect your work. Be certain that none of the many wires going to the panel switches are shorting against each other. Make certain that no stray wire strands from you switch wiring are laying on the PCB anywhere. The can short out your PCB since there is no soldermask. Enjoy your 822 module. The 822 and 831 are limited run modules that will not always be available. The first 50 copies of 822 are now sold out. I made a second run of 100 PCBs, but that will be the end of it. Hidden feature: Because the 831 is limited to 50 and the 822 to 150 copies, I am offering official serial number tags for the bottom of your mounting bracket (or wherever you decide to put it). Serial numbers will be assigned by the order I receive requests Serial #s 001 and 002 belong to me. I am putting this information here only, just to see who actually reads the instructions to this point. Shush.... Mums the word. Drop me a note and I will send your serial numbers right out. Now you are ready for calibration. There are two calibration docs. You do not use both. You use one or the other. One is for those that prefer to calibrate primarily by ear while the other allows full calibration with only a nice voltmeter.