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Erica Synths version of the Polivoks VCO uses the core of the original Polivoks VCO, and DIY kit, as all Erica Synths Polivoks modules, comes with a set of the

original Russian ICs and transistors.

Same time, there are plenty of changes in the schematics. We:

1) changed CVs to eurorack standard 1V/Oct (original has inverted CVs)

2) made all CV ins buﬀered in order to eliminate crosstalk and undesired detune (very few DIY kit producers buﬀer CV ins - mostly they are just summed on

resistors)

3) made optional adjustments to output signal amplitudes and oﬀsets - you can have the original output signals (they are totally diﬀerent waveform to

waveform) or make them standard 10Vptp

4) original Polivoks has interesting peak in the triangle waveform - we introduced optional ﬁlter to eliminate it or leave as it is

5) we signiﬁcantly updated pulse wave circuit and introduced PWM - it sounds insanely great!

GUIDE ON ASSEMBLY OF THE ERICA SYNTHS SUPER-ENHANCED POLIVOKS VCO

Summary of content (12 pages)

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GUIDE ON ASSEMBLY OF THE ERICA SYNTHS SUPER-ENHANCED POLIVOKS VCO Erica Synths version of the Polivoks VCO uses the core of the original Polivoks VCO, and DIY kit, as all Erica Synths Polivoks modules, comes with a set of the original Russian ICs and transistors. Same time, there are plenty of changes in the schematics.
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PLEASE FOLLOW INSTRUCTIONS BELOW TO COMPLETE THE MODULE SUCCESSFULLY!
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➊ Take precautions with regard to electrostatic discharge (ESD) safety. Handling components should be done in electrostatically safe environment. Use personal and workplace grounding. Any discharge (even a minor one) from body to a component may permanently damage it.
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➌ Populate PCB with resistors and diodes. NB! PCB V3.1 HAS MISTAKEN SILKSCREEN; YOU HAVE TO SWAP TWO RESISTORS: R68 HAS TO BE 2K7, AND R3 HAS TO BE 1K. IF YOU DO NOT DO SO, YOU WILL NOT BE ABLE TO TUNE THE VCO. The PCB has silkscreen both of resistor values and designations. I strongly recommend using all 1% resistors, especially, if you are building both VCOs, but if you do not do so, there are several resistors that MUST be 1%. Those are mentioned in the schematics and noted with * on the PCB silkscreen.
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➎ Solder IC sockets and trimpots. Solder OP2 – it has to be soldered directly without the socket. Solder PSU socket. ➏ Solder transistors! See the picture below that helps to identify the transistors. KT315 are NPN transistors, KT361 is PNP transistor. Colors of cases may vary, but the main thing is that KT361 has cyrillic letter G in the middle of the case.
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➐ Soviet transistors (KT315 and KT361) are sensitive to light, including infrared. If you do not intend to tune the VCO in the darkness, it’s time for real DIY challenge! We will use the copper sheet included in the kit to make the shield for transistors. a. b. c. d. e. f. g. h. a. Use the TEMPLATE below to cut out the shield! b. Use pliers and, if needed, a small hammer, to bend sides of the shield. You have to end up with a small box. c.
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➑ Solder potentiometers ➒ Insert ICs. Mind the orientation. 10 Wash the PCB to eliminate the ﬂux 11 Install jacks and switches (if you are using rotary switches provided with the full kit, use special washers to conﬁgure them to 5 and 6 positions correspondingly) in the front panel. Connect all GND lugs of the jacks to the GND of the PCB. Note that R64 is oﬀ board and goes from PWM jack to the rotary switch S2.2.
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ERICA SYNTHS POLIVOKS VCO WIRING 1V/OCT OCTAVE 9 10 11 8 7 6 5 A 12 1 2 4 3 9 10 11 8 7 6 5 A C 12 1 2 X-MOD IN 20 K LIN FM IN OUTPUT PWM IN 4 3
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TUNING THE OSCILLATOR Ensure all components are placed correctly and soldered well. Check for possible short circuits that may be leﬅ aﬅer soldering. Ensure power supply voltages are as exactly +12.00V and -12.00V as possible. Allow some minutes for the VCO to warm up. --Connect a precise voltmeter with range at least +/-15V to the Test Point 1 (TP1). Apply 5.00V to CV input. Set panel FREQUENCY pot to 12 ‘o’clock. When tuning VCO2, set DETUNE pot to 12 ‘o’clock. Set CV level pots to zero.
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Roland, ARP, Sequential Circuits or Moog analog synthesizer compatibility. --Select PWM 50 waveform. Ensure panel that both modulation pots are set to minimum. FREQUENCY and octave can be set to any frequency comfortable for listening and display. Connect an oscilloscope to the VCO module output. Adjust trim pot TP6 so that duty cycle of the waveform is about 50/50. Select PWM 25 waveform. Adjust trim pot TP7 so that duty cycle of the waveform is about 25/75. Select PWM 12 waveform.