117
P M 3 3 9 4 , F L U K E & P H I L I P S
c h 3
c h 2
c h 1
c h 2 : p k p k = 7 . 1 4 V
c h 3 : p k p k = 1 1 . 9 V
C H 1 ! 5 0 0 m V =
C H 2 ! 5 . 0 0 V =
C H 3 ! 5 . 0 0 V = A L T M T B 5 . 0 0 u s - 2 . 7 4 d v c h 1 +
1
2
3
T
P M 3 3 9 4 , F L U K E & P H I L I P S
c h 4
c h 3
c h 2
c h 1
c h 1 : f r e q = 3 1 . 5 k H z
c h 3 : d c = 7 0 . 9 V
C H 1 ! 1 0 . 0 V =
C H 2 ! 5 0 . 0 V =
C H 3 ! 5 0 . 0 V =
C H 4 ! 1 0 . 0 V = C H P M T B 1 0 . 0 u s c h 1 -
1
2
3
4
T
Dynamic Focus 1 – B+ Mfg.
This first half of the dynamic focus circuitry stage consists of several parts:
1. Horizontal ramp manufacture
2. PWM manufacture
3. Current and voltage amplification
4. Regulation
Horizontal Ramp Manufacture
Charging capacitor C1615 at IC1502/pin 8 creates a ramp signal (ch 2).
Q1614 resets the ramp by using the horizontal pulses. The resultant ramp
is at the horizontal scan frequency.
W a v e f o r m D F h – R a m p O u t p u t
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
F B T
P r o b e a t F B T
N / A
C h a n n e l 2
R a m p in p u t
I C 1 5 0 2 / p in 9
7 V p - p
C h a n n e l 3
P u ls e O u t p u t
I C 1 5 0 2 / p in 1 4
1 2 V p - p
T im e b a s e
5 u s e c / d iv
Pulse Manufacture
The horizontal rate ramp signal is input at IC1502/pin 9 and a DC voltage
is input at pin 8 of this comparator. This DC voltage input at pin 8 governs
the output pulse width at IC1502/pin 14. When a normal 4:3 ratio picture is
requested by Main Micro IC3251 (not shown), D/A Converter IC1702/pin 1
is LOW (1.7Vdc). When a wide 16:9 (called Full, CC, Zoom or HDTV)
picture is requested, D/A Converter IC1702/pin 1 is HIGH (9.7Vdc).
A 4:3 ratio picture produces a narrow low going output pulse. A wider low
going pulse is output during a 16:9 aspect ratio picture. The signals manu-
factured during a 4:3 and 16:9 picture can be seen in the waveforms be-
low.
W a v e fo r m D F a – N o rm a l 4 :3 a s p e c t r a tio p ic tu re
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
D F - V
C N 1 3 0 3 / p in 1
1 2 V p - p
C h a n n e l 2
A m p lif ie d D F - V
Q 7 0 0 9 /D
1 3 5 V p - p
C h a n n e l 3
B + t o D F T
T 7 0 0 1 /p in 1 1
7 1 V d c
C h a n n e l 4
D F - D e t
C N 1 3 0 3 / p in 2
7 V p - p
T im e b a s e
1 0 u s e c / d iv
Содержание DTV-01
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