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Power Supply Before turning on, set PR1 cw and PR2 ccw with only ‘A’ board plugged-in. Set PR2 for +12V ± 0.1V Set PR1 for -9V ± 0.1V Check PR2 again and reset if necessary N.B. -9V rail is parasitic on the +12V supply. Plug in ‘B’ and ‘C’ cards and recheck +12V and -9V rails. These should not have altered. If they have, suspect either ‘B’ or ‘C’ board orpoor regulation on A board. Plug-in keyboard as extra load. +12 and -9 Volt rails should not have moved more than ± 0.1V measured always on the ‘A’ board. (‘C’ board voltage may be 20 mV lower) Monitor the rails on the scope (5mV/cm). Look for hum and noise. These should be much less than 5mV. Noise, if present, will probably be due to the zener diode.
N.B. A2 normally gets hot, dodgy Dl gives large 100Hz ripple on Output. Always clean edge-connectors and check clean presets on ‘A’ board. |
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Connect full level ramp signal at 261 Hz from Oscillator 1 to both Outputs.Trim PR4 and PR5 for minimum signal breakthrough. (Maximum 5mv p.p) Replace presets if adjustment is erratic. Reset Output Channel row controls to 5.0.10.5. Output levels should be around 1V p.p and should be within 20% of each other. Check signal tracking in thesame manner for Output settings 4 and 6 as well. If one level is consistently high, pad out resistor across its control pot (R305 = 56K) Successful tracking will depend on the characteristics of the pots and the correct matching of the FET’s Q14 & Q18. Connect the joystick row via two shorting pins to both VC level inputs. Swingstick up and down to check for 20% level tracking tolerance.(Level pots shouldbe at zero). Inaccuracies in stick tracking may be adjusted by altering thevalue of R302 or R304 (lOK) which are mounted under the patchboard rear. Check correct operation of Pan controls, which only affect the Signal Outputs. Check also the Output Filters. Use noise as a good source. Check for max. outputs on the Signal Output socket of at least 2.5V p.pbefore the onset of clipping. Level controls should be at about 6. Checkheadphone signal is good. Check for instability of Output Amps by driving hard with low frequency. (Oscillator 3 square wave). The level control of thechannel NOT being driven should be on zero. Monitor the two signal outputs.The undriven channel will show breakthrough. Plug in headphones and check for oscillation. Reduce drive to Output Channel 2. Keep checking for oscillation.Then repeat for other Output Channel. N.B. DC offset across loudspeaker is 1.8V ± 10%. |
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Reverberation Set PR3 fully clockwise before operating. Feed large amplitude tone bursts into reverb. Adjust PR3 so that the output is dry at Mix setting of zero and reverberation progressively increases from setting of 2. Maximum dryness on the Mix control should be no worse than thatobtained with the VC Mix input row on the patchboard grounded. Check voltage control of Mix with the joystick. Hold input amplitude constant and sweep frequency of tone. Check for rattles, buzzes or abnormal resonances in the spring. Check spring is correct way round. If Mix control is wrong change Q10. N.B. Reverb amplifier should clip symmetrically. |
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Filter
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Filter With Response on 10, level full and Frequency on 5, check for oscillation.About 1.5V p.p. should be obtained. The shape should be reasonably sinusoidalespecially when only just oscillating (on Response control). Distortion should be eliminated either by diode bridging or by replacement of offending diode. Bad diodes can be detected by applying the tip of a soldering iron quickly to the diode body. Allow enough time for the diode to cool down before moving on to the next one. Response control should make the filter oscillate only above 5 for all frequency settings. If this does not occur correctly, adjust R90 or suspectwrong Vp FET. Frequency range on the Frequency knob should be roughly lOHz to 12kHz. If oscillations stop at one extremity of Frequency pot increase R75. Adjust PR6 for oscillation frequency of 261Hz with F on 5. Noise level of Filter output signal with Response set below point of Oscillation, thisshould be below 5mV p.p. Check correct filtering using square wave input with swept F. Intermittent noise: Try soldering iron tip on diodes. Adding a 1M ohm resistor (R288) stops Filter latching- up, and is mounted across Q44 and Q45 emitters. |
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Ring Modulator Use filter sinewave output, Frequency on 5. Maximum response, maximum level into both inputs of "ring modulator. Ring Modulator level maximum. Check output is double frequency of input, and at least as big. Remove pin to Input B. Drive input A and adjust presets for minimum breakthrough. (PR9 - second harmonic rejection, PR10 - fundamental rejection). Drive Input B by removing pin to Input A and reinserting pin for Input B. Trim presets for rejection. (PR8 - second harmonic, PR11 for fundamental). This one should NOT drift. Input A drifts quite a bit and should ideally be adjusted with the back on the machine after it has fully warmed-up. If thisis not possible ensure that Input B is used for the continuous signal to minimise breakthrough. With an input level of 1.5V p.p up to lOmV p.p maximum is allowed for breakthrough. This gives about 60 dB rejection. If higher harmonics are a problem, then filter signal must be too impure. Try backing off response, or use an external signal generator. 1.5V p.p at 261 Hz. If reasonable rejection is unobtainable, change matched pair BC169C or TAB101 where appropriate. 2C746 used on later models. Do not bridge with resistors. Replace presets if adjustment is erratic. internal note from Patrick: you can see on the scope that the Waveform gets more Voltage or less - you need to move the Waveforms to the 0V direction (same for the TTSH calibration) |
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internal note from Patrick: few users and on my 5 Cloneys are 1nF Capacitors used to get the correct Frequency with the verniers (6 = 261hz and 8 = 2088hz) I used silver mica, styrene and C0g caps - select pairs within 1% !! don't use polyester caps or the VCO isn't stable (temperature drift) Oscillator 1 The first operation is to adjust the shape of thesinewave, since the adjustment affects frequency. Using the vernier control and PR15 if necessary, obtain an output of 400Hz. Turn the ramp down and adjust the sine shape control for the best sine shape.Trim PR17 to balance out the spike on the peak of thesinewave. This may best be seen by expanding the X and Y inputs on the scope. The best position is where the small spike is triangular and balanced. A small thin spike may also appear but is not important. Test the main shape control. A good sine wave should be achieved on 5.Set PR16 halfway and leave it alone. Set frequency vernier dial to 6 (±% division). If further out, R197 or R201 may need to be adjusted.
Sine Output should be around 1.5V p.p RampOutput should be around 1.5V p.p N.B. Ramp shape is not controllable. Pitch characteristic is 0.32 Volts/Octave. Oscillator 2
Tracking Mix Osc. 1 and Osc. 2 ramp outputs into Output Channel 1. Use PR20 only to trim the tracking of Osc. 1 and Osc 2. Using the joystick on max with range control to limit frequency range. Set both verniers to 6 and tune for zero beats. Advance the joystick range control, which will increase both frequencies until the beats begin. Trim PR20 to zero beats, and remember which way you turned it. (N.B. The preset is a very fine adjustment, and when the tracking is nearly right it will be necessary to make very very small movements). Having trimmed PR20, turn the range control back to zero, re- adjust one of the verniers near 6 to give zero beats and then advance range control of joystick to where it was before. If beats are faster you know you turned the preset the wrong way. Repeat procedure until tracking goes to about 2kHz. Ideally a test 'back’ should now be fitted and a final adjustment made after another 10 minutes have elapsed.
N.B. Always use specially matched 2K7 pins for tracking tests. Oscillator 3
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