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Theory of Operation
1780R-Series Service Manual
3–79
Deflection Amplifiers. The amplifiers are nearly identical. The Vertical Amplifier,
which has VHF Compensation (C614), consists of Q611 and Q617 (a differential
pair) and Q710 and Q719 (grounded base amplifiers) that speed up the amplifier
by minimizing the Miller capacitance of Q611 and Q617. Q515 and Q516 are the
current source for the differential pair.
The Horizontal Amplifier consists of Q623 and Q628 (a differential pair) with
Q723 and Q730 (grounded base amplifiers) that speed up the amplifier. Q526
and Q527 are the current source for the differential pair.
The Othogonality adjustment (R511) feeds a vertical (X) signal into the - input
of the Horizontal Deflection Amplifier. About +2% of the Y signal is fed into the
X signal for orthogonality compensation. Adjusting the orthogonality control
cancels out some or all of the Y signal in the X Amplifier to change the
deflection angle between the X- and Y-axis and compensate for CRT geometry.
The input signals for the Deflection Amplifiers are also routed to the Vectorscope
Z-Axis Amplifiers for blanking/unblanking the CRT.