Tektronix 3B5, Инструкция по эксплуатации

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Circuit Description — Type 3B5
zener diode D375 sets the level at the emitter of Q374 to
— 6 volts. Since its base is held near zero volts, Q374 is
reverse biased. The collector of Q374 goes negative toward
the —100-volt supply and is clamped near —12 volts by
D374. This voltage level remains constant over the entire
sweep for X1 magnification. This level is coupled to the
CRT grid circuit through terminal 14 of the interconnecting
plug.
For X10 delayed sweep magnification, the anode of
D371 is held at —12 volts by the X 1 magnifier logic and
it is reverse biased. The X 1 00 magnifier logic remains at
— 12 volts and D375 holds the emitter of Q374 at —6 volts.
When the X10 Magnifier Gate stage is turned off by the
Delay Comparator, the negative voltage at its collector is
connected to the base of Q374 through divider R371-R372-
R373. Q374 is forward bisaed and its collector rises positive
(less negative) to about — 6 volts. This voltage level deter­
mines the display intensity for the magnified portion of the
trace only.
Operation of the Delayed Sweep Magnifier Intensifier is
basically the same for X 1 00 delayed sweep magnification
as for X10 except that the output is more positive to intensify
the trace more. The X 1 00 magnifier logic level to the
anode of D376 is zero volts for X1 00 delayed sweep mag­
nification. This sets the emitter level of Q374 near zero
also. Now as the X10 Magnifier Gate switches off, the
collector of Q374 rises positive to about zero volts. The
grid of the indicator oscilloscope CRT is raised more positive
to provide a brighter intensity for the magnified portion of
the trace only.
Delayed Sweep Magnifier Readout Control
The Delayed Sweep Magnifier Readout Control stage indi­
cates when the basic sweep rate is magnified (except for
basic sweep rates of 0.5 microsecond/division and faster).
The X 1 magnifier logic level is connected to the base of
Q344 through D345 and divider R345-R346-R347. For X 1
sweep magnification, the XI magnifier logic level is —12
volts and Q344 is reverse biased. Current does not flow
through the readout bulbs. For X10 and X 1 00 delayed
sweep magnification, the X 1 magnifier logic level is zero
volts. Q344 is turned on and its collector goes negative to
about —12 volts. Current flows through B982 and B983,
MAG ’ D SWP readout. In the 0.1 μ s and 10 ns timing
decades, the “h ” decade logic line is at — 12 volts. This
level is connected to the base of Q344 through D344 and
divider R346-R347. Q344 is again reverse biased and the
indicator bulbs turn off. This logic level over-rides the X
magnifier logic level. Since the magnifier is used to pro ­
vide the basic sweep rate when using the 0.1 μ s (h) timing
decade, the delayed sweep magnifier is not operable and
the MAG'D SWP readout is locked out.
Horizontal Amplifier
General
The Horizontal Amplifier provides the output signal to the
left and right deflection plates of the indicator oscilloscope
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