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Oakley Sound Systems Oakley Modular Series OMS-820 issue 2 The MOTM-820 Companion Module User’s Guide V2.01 Tony Allgood B.Eng Oakley Sound Systems CARLISLE CA4 9QR United Kingdom...
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GATE, on the front of the OMS-820. When in AD (attack-decay) and Gated mode, the output of the MOTM-820 will then rise until +5V is reached, whereupon it will fall back to zero. Rise and fall times are governed by the MOTM-820 of course, and fully voltage controlled.
MOTM-820. No component changes are required to the MOTM-820 at all. Inserting a jack plug into the IN socket of the MOTM will override any control signal sent by the OMS-820. The MOTM-820 will then behave as a conventional VC Lag module.
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U1 (pins 5,6,7). This output is now negative, so the MOTM-820 now forced to discharge, and hence its own output will fall. The falling voltage now causes pin 3 to slowly fall from a positive value back to zero. And once...
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9. When the flip-flop is latched, pin 10 goes high and pin 4 goes low. The output at pin 10 is passed via R16 to the MOTM-820’s input, thus causing the MOTM to start to charge upwards. R16 is chosen to interact with the MOTM’s input impedance of 100K to give an input signal of 7.5V in the high state.
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R6. R6 controls the sensitivity of the circuit. 1K produces about 5 mA through the LED for a 5V output of the MOTM-820. The other three LEDs are driven in a current chain. The chain is driven from a current sink Q1 and associating circuitry.
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DOWN points in the MOTM-820. These allow the MOTM-820’s own pots to be used as input attenuators whilst being able to set the absolute rise and fall times with the OMS-820. Feel free to make any changes to the circuit to improve or alter the performance. If you do, do drop the Oakley-Synths mailing list an e-mail and tell us all what you have done.
U4 is a 4001 device, and is part of the classic 4000 series of CMOS logic. Many companies make this device and as such the device ends up having all sorts of names. eg. CD4001, MC14001, 4001BE. All types should work but try to avoid the 4001UBE, this is an older device and is very prone to static damage.
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390R Capacitors 100nF polyester film 5mm box 10nF polyester film 5mm box 1nF polyester film 5mm box 22uF, 35V radial electrolytic 2u2, 63V radial electrolytic Discrete Semiconductors 1N4148 or 1N914 signal diode BC549 or BC550 NPN transistor BC559 or BC560 PNP transistor LED 5mm Bicolour LED LED 5mm Red LED LED 5mm orange/yellow LED...
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Populating the Oakley OMS-820 PCB Warning: Oakley Modular PCBs are now supplied with the RoHS compliant Ni/Au finish. This is a high quality finish but does possess slightly different soldering characteristics to the traditional lead based HASL finish. Handle the boards with care, and avoid touching the Ni/Au that can cause premature tarnishing of the finish.
The smaller electrolytic capacitors are very often supplied with 0.1” lead spacing. My boards have a hole spacing of 0.2”. This means that the underside of these radial capacitors will not go flat onto the board. This is deliberate to allow the water wash to work, so don’t force the part in too hard.
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NOTE: This procedure is rather different to that of the Omeg/Piher pots you may have used on the older Oakley boards. The first thing to do is to check your pot values. Spectrol do not make it that easy to spot pot values.
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Note that the pot shafts of the two pots will not need cutting to size. They are already at the correct length. Connections The power socket is 0.156” Molex/MTA 4-way header. Friction lock types are recommended. This system is compatible with MOTM and standard Oakley Modular systems. Power +15V Module GND 2...
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The SCR pad on the PCB has been provided to allow the ground tags of the jack sockets to be connected to the power supply ground without using the module’s 0V supply. Earth loops cannot occur through patch leads this way, although screening is maintained. Of course, this can only work if all your modules follow this principle.
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We will deal with each pin of the 0.1” socket in turn. Pin 1: connect to the signal lug of the socket on the MOTM-820 labelled OUT1. It will already have a wire connected to it from the MOTM PCB. Make sure when you solder the new wire onto the lug, the old one doesn’t fall off.
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OUT LED rise, and stay on. Pressing RESET should slowly extinguish it. Check that the UP and DOWN pots on the OMS-820 actually do what they should. They should simply replicate the ones on the MOTM-820. If that all works, you should have a completely working module.
Group that can be found at http://launch.groups.yahoo.com/group/oakley-synths/ If you can't get your project to work, then Oakley Sound Systems are able to offer a 'get you working' service. If you wish to take up this service please e-mail me, Tony Allgood, at my contact e-mail address found on the website.