Circuit Description— Type TU-7
+ 75 v |
L
+ 67.5 v
+ 6 7 .2 v
Ov
— 0.6 v
+ 6 7 .8 v
+ 6 7 .5 v
+ 60 v I
I
Fig. 3-8. M a jo r current p a th du rin g rise and top o f pulse w ith TEST FUNCTION sw itch a t + PULSE an d AMPLITUDE con trol fu lly clockwise.
Q64 and Q74 in cutoff. With no current through Q64 and
Q74, the disconnect diodes are forward biased and are
conducting current from the supply voltages through R62/
R64/R66 and R72/R74/R76. Current through the disconnect
diode circuit and thus through the output resistors (R66/R76)
is adjusted by ganged AMPLITUDE controls R62/R72. The
output voltages are applied to pins 1 and 3 of the inter
connecting plug and produce the baseline voltage on the
crt display of the +pulse. With the AMPLITUDE control
turned fully clockwise and the disconnect diodes conduct
ing, this output is approximately +67.2 volts at the junc
tion of D75 and R76, and approximately +67.8 volts at
the junction of D65 and R66.
During the time that Q55 is cut off, C52 and the capac
itor selected by REPETITION RATE SW50 charge to ground
through R53, and the voltage in the emitter circuit becomes
more negative. As the base-emitter junction of
Q55 be
comes forward biased, this transistor turns on and causes
the multivibrator to switch states. As Q55 turns on and Q45
turns off, the base-emitter junctions of Q64 and Q74 become
forward biased, turning on these transistors and shunting
Fig. 3-9. M a jo r current p a th du rin g fa ll and bottom o f pulse w ith TEST FUNCTION a t + PULSE and AMPLITUDE control fu lly clockwise.
3-9
