Moog Source - Page 8

INCREMENTAL CONTROL CHECK. BOARD 3
MODULATION OSC RATE
Connect DVM to pin 7 of U13B and scope to pin
7 ot U48B. Turn MOD RATE control to obtain 5.2V
reading. Adjust RANGE trim R223 for 7Hz (142.6
msec) +/- 0.5Hz.
DUTY CYCLE
Attach a dual trace scope at U19 pin 6 («1) and
U19 pin 4 (p2). Rotate incremental control and note
pulse duty cycle should be nominal 50% */- 25%.
Check clockwise and counterclockwise rotation.
GLIDE TIME
Set GLIDE to 99. Adjust RANGE trim R19 to
yield glide time from low C to high C and vice versa
between 3 to 5 seconds.
PHASE RELATIONSHIPS
Using same setup as above, check phase of the
positive edge of pi in comparison to p2 at approxi¬
mately 250 RPM (1kHz output frequency). Positive
edge of pi should be at 50% +/- 10% of p2 pulse
width. Since adjustment of phase requires a change
in gap between VQ1 and VQ2 OPTO interruptors,
malfunctioning unit should be replaced with a factory
adjusted assembly.
CHIP TEMPERATURE ADJUSTMENT. BOARD 2
NOTE
Oscillator chip temperature is factory set
and should not need further adjustment.
Do not adjust unless the oscillator 1C or
components in the temperature compen¬
sation circuit are changed or proper tuning
can not be accomplished.
REPLACEMENT PARTS LIST
OSC 1 CHIP TEMPERATURE ADJUSTMENT
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Turn TEMP trim R131 fully counterclockwise
(wiper at -0.6V) and leave in this position for about
10 minutes to allow chip to cool to room temperature.
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a) Measure emitter voltage of Q15 (pin 3 of U34)
with respect to ground (use 1K in series with probe)
and record reading (Vq).
b) Estimate room temperature in degrees C (T R ).
c) Subtract room temperature from 55°C to
determine temperature rise needed to reach 55°C.
d) Multiply result by 2mV. (Transistor VBE de¬
creases by 2mV/°C.)
e) Add this product to cold reading (Vg)
measured above to determine hot reading (V|_|).
Example: T R = 22°C (72«F): V c - -616mV;
V H " V c + 2 (55 - T r )
-616 + (2 x 33) - -550mV - VH
f) A djust TEMP trim R131 to obtain reading
determined above at emitter of Q15 (U34). Chip
temperature now set at 55°C.
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OSC 2 CHIP TEMPERATURE ADJUSTMENT
Set Up the control panel the same as for Osc 1
and follow the same procedure except TEMP trim R83
is adjusted to set voltage at emitter Q8 (pin 3 of U26).
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