Tektronix WFM601, Service Manual

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Theory of Operation
3–14
WFM 601 - Service Manual
G/Y component of the Monitor Output to increase in brightness whenever a
gamut limit is exceeded, if the Monitor gamut alarm is enabled.
A gamut inhibit signal is generated by the Coprocessor, Diagram 4, which
inhibits the Monitor gamut alarm brightup, if the function is not enabled. If the
brightup is enabled, the gamut inhibit signal toggles on and off at about 2 Hz,
which causes the brightup of gamut errors to flash on the monitor.
In addition to being the brightup amplifier for gamut limit errors, U76 inverting
input is a summing junction where composite sync is inserted for the G/Y
Monitor Output to synchronize a picture monitor. U74A is an inverter and Q441
an emitter follower driving both the Monitor Output and the Horizontal
Reference Multiplexer on Diagram 11.
The Monitor Output amplifiers are identical clamped amplifier circuits, capable
of driving a component picture monitor. Input signal can be either color
difference or GBR, with composite sync added to the G/Y component.
Clamping is to ground, controlled by a clamping pulse generated by the
Coprocessor. Each input has a flatness compensation, C711, C721, and C731.
R85, R95, and R105 set the output impedance to 75
for each of the channels.
Monitor Output