Theory of Operation-314 Service
at any intensity setting, once the Astig control has been
set.
Geometry Control R575 adjusts for minimum bowing of
horizontal and vertical traces within the graticule area.
Trace Rotation control R563 sets the current in the
Trace Rotation coil, creating a magnetic field through
which the crt electron beam passes. This current permits
the horizontal trace to follow a path parallel to the
horizontal graticule lines.
Blanking and Unblanking
Signals for unblanking come from oneof threesources:
Sweep output (U430, pin 15, -Gate), thevertical switching
circuit (chopped mode), or the EXT BLANK connector on
the rear panel.
The Unblanking amplifier (consisting of
(2723, Q730,
Q734, Q744, (2745, and associated circuitry) provides crt
beam blanking during sweep retrace and during switching
interval in chopped mode.
C655-R656 hold the undriven blanking plateat a higher
potential than that of the driven plate for a brief period
after oscilloscope turn off. This voltage blanks the crt
beam until the high voltage power supply discharges and
the crt heater cools.
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