Fluke Autoranging CombiScope PM3370B Service Manual page 321

UNIT DESCRIPTIONS
Intensity control circuit
All conditions under which the Z-control circuit has to switch the CRT beam ON and OFF are combined
in the intensity control circuit. The intensity information comes via the SBUS (serial BUS) to the six
channel DAC N8070. Selection between text intensity, trace intensity normal and trace intensity
intensified is done in multiplexer D8059 which is controlled by the signals BI0---HT and BI1---HT.
Text intensity
Normal trace intensity
Not used
Intensified intensity
The selected signal is applied to the base of transistor V8004. Symmetrical Z-control output signal
pair ZTXT0 and ZTXT1 carries the resulting blanking/unblanking information which is, applied to
R3007 and R3008 on unit A2 in the analog oscilloscope section.
Information for the analog oscilloscope section about switching between the analog Z-signal and the
digital Z-signal, is derived from signal BZSW--HT (low is analog trace intensity and high is digital trace
and text intensity) via transistors V8042 and V8033 and applied as current signals ZSW0 and ZSW1
to D3001/7 and D3001/8 on unit A2.
Signal BZTE is low for unblanking and high for blanking of the trace. In analog oscilloscope mode,
signal BZ1 switches between holdoff (low) and sweep (high). In digital oscilloscope mode this signal
switches between text display (low) and trace display (high).
5.8.1.13 Diagram 13
Display interface
Frequency divider:
The 40 MHz input clocksignal CK40M is divided via circuit D8055 into a TEH pulse and a 50 ns
SCPULS pulse for the control of the VECTOR (dot join circuit) circuit N8061.
25 ns
(40 MHz)
CK40M
BTEH--HT
SC pulse
TEH
Final offset:
Final offset levels for the X- and Y-axis in the dot join mode, are generated via the SBUS (I2C BUS)
and N8009 as levels XOFFS and YOFFS. These levels are via transistors V8201/V8199 and
V8203/V8204 applied to the XDAC0/XDAC1 and YDAC0/YDAC1 level signals from the X- and Y-
DAC on diagram 12. Resulting X- and Y-signal information is applied to the VECTOR circuit N8061.
BI1
0
0
1
1
50 ns
BI0
0
1
0
1
300 ns
300 ns
300 ns
5.8 - 21
ST6805