TM 5-6675-318-14
(d) Conduction of transistor
Q3 pulls the center tap of drive pulse
transformer T1 to common which disables
the series switch transistor A9-Q1. Conduc-
tion of transistor Q2 provides a current
path for transistor Q1 which starts to
conduct and cuts off transistors Q3, Q4,
and Q5, allowing the slow turn-on/off
sequence circuit to be activated.
(e) Conduction of transistor Q1 occurs when the voltage of capacitor
A9-C24 reaches a predetermined level and turns off transistors Q3, Q4, and Q5,
signifying the start of operation of the power supply.
(f) Turn-off is initiated when the plotter is switched off. Transistor
Q 2 turns off, which turns transistor Q1 off and Q3, Q4, and Q5 on until capacitor A9-
C 2 4 discharges.
The conduction of transistor Q3 during the off transient period
inhibits transistor Q1 from turning on.
(7) Power-on detection generation circuit.
Resets
plotter
for
initializa-
tion.
( a ) A power on (PWR ON) signal is generated on PCA A10 which is used to
s e t a power-up (PUP) driver on PCA A3.
PUP clears or sets the plotter circuits to a
known quiescent condition when the plotter is first switched on. This PUP signal is
at a low logic level initially. Then it switches to a high state after the initial
warm-up period and remains in a high state until the plotter is switched off.
(b) When the plotter is first switched on, the regulated +15 V supply
f r o m U1 on PCA A9 is outputted to the resistive divider consisting of A10-R54 and
A10-R55.
T h e output of this divider, which is approximately +2.26 V, is compared
w i t h the initially low +5 V (A) supply by voltage comparator A10-U4D which provides
a low input to voltage comparator A10-U4C, causing its output to go high. This high
o u t p u t turns on transistor A10-Q11, which pulls the power on (PWR ON) output line
l o w and activates the power-up (PUP) driver circuit on PCA A3. When the +5 V (A)
s u p p l y output comes up to full voltage across voltage divider A10-R56 and R57, the
output of divider (+2.5 V) is applied to the non-inverting side of voltage compara-
tor A10-U4D causing its output to go high.
T h i s high output allows C19 to charge to
+5 V through A10-R58.
With a high input to U4C-8, its output goes low, cutting off
t r a n s i s t o r A10-Q1 and allowing the pwr on line to float up to the switched +5 V (A)
level.
Autogrip power.
Is supplied by the autogrip circuitry, which is in the
p o w e r supply assembly and is part of PCA A10.
A secondary winding of T4 supplies
1 1 0 V to generate the platen voltage.
The 110 V is applied to a voltage multiplier
( C 2 0 1 - 2 0 4 and CR203-206) which boosts the voltage up to approximately 500 V.
When the chart hold signal is low, transistor Q101 is turned off and relay K101 is
normally closed. With relay K101 closed, the input to the voltage multiplier (at
C201 and C204) is grounded through relay K101 and the platen voltage is 0.
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