Yamaha CT-7000 Service Manual page 13

2-3. Potential at points@ and@ becomes that shown
at a· b' c' and d' in the chart 10 and 11 . Phase differ­
ences and output relations between pilot signal and
detection signal are as shown in the following chart 12.
Since points@and@ are connected to the differ­
2-4.
ential amplifier, its operation creates the following
relations. Let the potential at@be E�\ at@, E� and
at @, E@. Then E@=K(E@ - E@). Furthermore
K>O. The output potential at e undergoes the change
shown in chart 12, also due to the phase difference bet­
ween the pilot signal and detection signal
Tr3.
3. Oscillation Section and Phase Comparison Detection
Section
The output potential of the phase comparison detec­
tion section is added to the base of Tr6 in the VCO,
so that by examining 1.b and 2-4 one can see that a
locked condition is possible only when the phase dif­
ference is either 90° or 270°, and the following con­
ditions hold:
a zone: VCO works for phase retard.
b zone: VCO works for phase advance.
c zone: VCO works for phase advance.
d zone: VCO works for phase retard.
Therefore the only stable, locked condition is 270°
phase difference (with a 90° difference, even a tiny
CHART 12
retard will cause an automatic shift to 270°).
Therefore, according to the charts in the Oscillator
Section discussions, what leads to stability are
nal output (chart 7), ® terminal output (chart 6),
CD terminal output (chart 3) and ® terminal output
(chart 2).
Even if a locked condition arises at 90° phase difference,
it will be due to(}) terminal output (chart
terminal output (chart 2), so that switching will not
be affected at all.
added to
j
PHASE DIFFERENCE
Q)
Difference between pilot signal and
CT-7000
Q)t
ermi­
and (fi)
3)
RENCE
terminal output signal.
CHART 13
1 1