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TM 11-6125-259-30
capacitors, etc. In detail, when the nominal +37 V
charge reaches a high level, the positive
at capacitors C401A and C401B reaches a low limit
voltage at camparator Z703-C input pin 4
it is sensed and corrected as follows. The low voltage
overrides the input at pin 5 and sets com-
output at capacitor C401A and C401B goes across
parator Z703-C output to low. In addition, the
resistor divider network R731, R732, R733 and
total amount of choke L201 current flow
R734. This voltage is compared with zener diode
through transformer T201 winding 7-8 also
CR707 reference voltage by comparator Z703-B.
effects the charge-up of capacitor C705. The
The output of comparator Z703-B is positive and
more current flow, the more voltage induced
goes to input pin 5 of comparator Z703-C and when
into the secondary of T201 which adds to the
it is a higher positive amplitude than the positive
voltage sent to capacitor C705 thus the less
time choke L201 center tap is shorted to
amplitude from capacitor C705 at input pin 4 of
Z703-C (to be explained below), then Z703-C output
ground. Note that during the time needed to
is high. This high will set comparator Z703-D
charge capacitor C705, choke L201 center tap
output to high which results in the following:
is being shorted to ground and the choke is
storing up energy to later be fed to capacitors
q 2701 nand gate input pine 1 and 2 are high
C401A and C401B for the +37 vdc supply.
causing a low at output pin 3 which sets flip-
This low established at comparator Z703-C
flop Z702 output pins 12 and 13 to the opposite
output will cause a low at comparator Z703-D
states (i.e., if pin 12 was high and pin 13 low,
output which in turn will cause all power
then pin 12 is now low and pin 13 high). This
switch transistors Q206, Q207, Q208, Q306,
causes Z700 nand gate output pins 3, 6 and 8,
Q307 and Q308 to be turned off (described in
11 to switch to opposite states so that trans-
detail below) thus removing the center tap of
isitors Q701 and Q700 now go to opposite
both chokes L201 and L301 from ground.
states from the lst cycle in which one of them
Therefore, chokes L201 will no longer store
conducted. Note that in the cycle just before
this, when comparator Z703-D was low, both
energy but will discharge energy; and also, the
logic will now be set so that the opposite choke
transistors Q701 and Q700 were turned on
L301 will be the next to store energy during
causing both chokes L301 and L201 to lose
the next storage cycle. After each choke L201
their center tap ground path through the
or L301 has stored up a given amount of
power switch transistors. If in this case trans-
energy, the low at comparator Z703-C output
istor Q700 base was at low from Z700 nand
will occur and stop the charging up of that
gate output pins 3 and 6, then transistor Q700
choke. The capacitor C705 charging circuit in
would be turned off and transformer T201
general will provide that when the 37 vdc is
secondary winding 5-6 would generate bias
low, choke L201 or L301 will be shorted to
voltage in primary winding 1-2 and turn-on
ground (to store energy) for a short time and
power switch trnsistors Q206 through Q208.
then, after a total discharge cycle, the other
This would cause heavy current flow in choke
Choke via flip-flop Z702) will be shorted; thus
L201. At the same time transistor Q701 would
establishing a push-pull operation.
be turned on by a high at its base, which would
result in current flow through secondary
In the case when the +37 volt capacitors C401A
winding 4-3 of transformer T801. This would
and C401B are not low and are at the proper +37
continue the turned off condition of transistors
volts, then the voltage at comparator Z703-B input
Q306 through Q308 and choke L301 center tap
pin 10 is high with respect to zener diode CR707
would not be Shorted to ground; L601 would be
reference input pin 11. The high at pin 10 will set
discharging any remaining energy into
comparator Z703-B output to low which sets
capacitors C401A and C401B.
comparator Z703-C output low which sets com-
q The high at comparator Z70-D output also
p a r a t o r Z703-D output low. This has the
causes a high at Z701-8 nand gate output (pin
following results.
8) which turns on transistor Q704 for the short
q Nand gate Z701 input pins 1 and 2 are low
RC time needed to charge up capacitor C704.
causing a high at output pin 3 which has no
The momentary turn-on of transistor Q704,
effect on flip-flop Z702 outputs but prepares
discharges the positive voltage on capacitor
the flip-flop to be switched at the next low from
C705 but, as stated above, transistor Q700 (for
Z701, pin 3.
example) will now be turned off thus allowing
q The low at comparator Z709-D output sets
the +15 volt supply current through tran-
nand gate Z700 input pins 2, 5, 10 and 13 to
sformer T201 winding 3-6 to diode CR705A to
low which sets outpins 3, 6, 8, and 11 to high.
charge charge up capacitor C705 again. When the
This high turns on both transistors Q700 and

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