Tektronix 1710J Series, Instruction Manual

Page: 93 / 252

Theory of Operation
1710J-Series Waveform Monitors
5–15
Table 5–2: Control Line Functions (Cont.)
Signal Line Result State
CAL Low Enables calibrator
LIN/FLD High 1 or 2 line display
Low 2 field display
TWO/ONE High 2 field or 2 line display
Low 1 line (no single field display possible)
X5 High Enables 5X vertical magnifier
EXT High Enables internal sync reference
Low Enables external sync reference
CH A High Enables CH-A input
CH B High Enables CH-B input
HMAG1 Low Enables magnifier in 2-line sweep
HMAG2 Low Enables magnifier in 1-line and 2-field sweep modes
3.58 Low Enables NTSC chrominance filter
4.43 Low Enables PAL chrominance filter
LPASS High Enables low pass filter
FLAT High Enables flat (no filter)
FIELDSWP High Enables field-rate sweep
ON DCR Low Enables DC restorer
GLITBLKEN Low Generates blanking pulse during H sync time in 2-line sweep
Under normal operation the base of Q856 is pulled down by CR955, which
causes Q855 to saturate and ground the amplifier output. When exerted the RGB
ENABLE, from the REMOTE connector, is inverted to provide a discharge path
for the emitter of CR955, which enables the RGB staircase amplifier.
The staircase signal from the REMOTE connector drives an operational
amplifier composed of Q856 and Q855, whose gain is approximately 0.5. The
amplifier is compensated, for optimum step definition (transient response), by
C953. R856, the RGB offset adjustment, compensates for input dc level
variation.
U331 divides down the microprocessor ALE output to generate cal drive. U331
is enabled by the CAL from the I/O data latch, U532.
RGB Amplifier
Cal Drive