Sony DTV-01, Manual

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91
P M 3 3 9 4 , F L U K E & P H I L I P S
ch4
ch3
ch2
ch1
C H 1 ! 5 . 0 0 V =
C H 2 ! 5 . 0 0 V =
CH3!1.00 V= BWL PKD
C H 4 ! 5 0 . 0 V = C H P M T B 1 0 . 0 u s - 1 . 4 6 d v c h 1 +
1
2
3
4
T
Horizontal Drive
H o riz o n ta l D riv e r / O u tp u t sta g e
B lo c k s M a jo r p a rts P u rp o s e
D ig ita l D e fle c tio n
C o n tro l
IC 1 3 0 5
C re a te s h o riz o n ta l d riv e
s ig n a ls .
B u ffe rs IC 1 7 0 5 , Q 1 7 0 2 ,
Q 1 7 0 3 . C u rre n t to v o lta g e d riv e r a n d
c u rre n t lim ite r.
P W M S h a p e r IC 1 5 0 2 S h a p e s th e H d riv e p u ls e in to
a s in g le s p ik e fo r P W M m fg .
Oscillator Manufacture and Sync
When powered, Digital Deflection IC1305 starts up the external X1301
24.58MHz crystal. Once oscillation occurs, the IC makes vertical and
horizontal drive signals. Without sync, the oscillator runs at 31.1kHz. The
horizontal drive signal leaves IC1305/pin 29 (as long as the vertical feed-
back signal at pin 11 is present - see Vertical Deflection). When station
sync is received, the horizontal oscillator frequency is changed to 31.5kHz
or 33.5kHz to match the signal received.
When a signal is received, its sync portion is squared into a 5Vp-p wave-
form by IC1302 and is input to IC1305/pin 35. The horizontal oscillator’s
frequency is fed back from the horizontal output transistor’s collector to
IC1306/pin 2. This signal is sent to a MMV (IC1306) that outputs a pulse
when triggered. IC1306 prevents a double input pulse from shifting the
horizontal oscillator frequency and produces a digital pulse that is accepted
by the Digital Deflection IC1305 at pin 26.
The Digital Deflection IC1305 compares the sync signal input to pin 35
and the feedback signal input to pin 26. This locks the horizontal oscillator
frequency to the station’s sync.
Buffers
IC1705 eliminates any base noise in the horizontal drive signal. It per-
forms this by comparing the input to a fixed voltage set by the R1743/
R1745 voltage divider at IC1705/pin 8. Voltages above this threshold are
allowed to pass and noise riding along the base line is not output pin 14.
The comparator output signal is 12Vp-p.
Q1702 and Q1703 are buffers/drivers that provide a fixed current to drive
the horizontal driver MOSFET device in the next stage (via CN1303/pin
10).
PWM Shaper
IC1502 is a comparator designed to shape the horizontal drive signal into
a single pulse for the next PWM stage. The input of IC1502 is the horizon-
tal drive signal and the output is a pulse that represents the leading edge of
the input signal. This pulse is output CN1304/pin 10 and applied to the
driver PWM stage.
Operation:
C1505 couples the leading and training edges of the horizontal drive signal
to IC1502/pin 11 (ch 2). Diode D1505 eliminates the negative or trailing
parts of the signal, leaving only the leading edges present at pin 11 (ch 2).
The comparator outputs this pulse (ch 3) when its input level is greater
than the fixed voltage at IC1502/pin 10. The result is a positive pulse at the
drive frequency. This pulse is used in the next stage to make B+ for the
MOSFET driver device.
The waveforms show the signals input the comparator with a horizontal
AFC feedback pulse (ch 4) for reference.
W a v e f o r m H D 1 e – I C 1 5 0 2 C o m p a r a t o r O p e r a t io n
N a m e L o c a t io n V o lt a g e / d iv
C h a n n e l 1 H . D r iv e s ig n a l C N 1 3 0 3 / p in 1 0 1 2 V p - p
C h a n n e l 2 C a p c o u p le d I C 1 5 0 2 / p in 1 1 9 V p - p
C h a n n e l 3 I C 1 5 0 2 o u t p u t C N 1 3 0 4 / p in 1 0 1 . 5 V p - p
C h a n n e l 4 H . A F C C N 1 3 0 2 / p in 4 8 5 V p - p
T im e b a s e 1 0 u s e c / d iv