Canon NP-70 Service Manual page 73

NP-70
3-33
3.3 SIGNIFICANT OPERATION TIMES
The importance of timing during the operations of the NP-70 cannot be overstressed. To aid in
understanding the general operation of the circuitry, the following breakdown of machine operation
time intervals is provided (reference-Fig. 3-4).
3.3-1 HEATER WAIT TIME
As the power switch is turned "ON", the NP-70 proceeds into a period of machine prepara-
tion, as shown in the ~ START
flowchart. This initial period is rather short and it cannot be
expected that the Heater Assembly temperature will rise sufficiently, even though the copier
is capable of copying in all other ways. Thus, the period in which "copying operation is possi-
ble but fixing is incomplete due to insufficient temperature" is designated Heater Wait Time.
Heater wait time is indicated to the operator by the flashing of the "Ready" lamp on the
front of the copier. The period of time of the flashing, however, will depend on the length
of the interval since the copier was turned OFF. The standard period of flashing will be
2 min. +15 secs ad'ustable b VR14 but at times it ma be shorter due to residual heat
—20 secs ( ~
y
)>
y
within the assembly.
For further information concerning this time, refer to the section on the Heater Wait Control
Circuit in 45.
3.3-2 WARM-UP TIME
Due to the design of the Timer Circuit, it is impossible to begin copy operations with the turn-
ing ON of the main power switch. This restriction is a built-in safety measure to allow the
copier a period in which it can prepare itself for copying. The designation for "the interval in
which copy is impossible due to machine preparation" is Warm-up Time.
The interval, of warm-up time is the first 21.7 second after the power switch is turned ON.
This time is determined by the charge time of capacitor C 13 (first 5.0 seconds) plus 4.17
revolutions of the drum. From the completion of warm-up time, the copier will proceed to
standby or begin copying operations.
It should be noted that the charge time of C13 will be 60.0 seconds in the event that the
copier temperature is below 15°C. In this case warm-up time will be 76.7 seconds.
3.3-3 PRESTART FOR THE FIRST FEED INTERVAL
At 17.0 seconds after the copier is turned ON, capacitor C16 will either begin its 8.0 second
discharge period (if no copy is to be performed) or it will be held until copy operations are
completed (by voltage through diodes D 16 and D 17, alternately). The 4.7 seconds between
this point and the completion of "Warm-up Time" is designated Prestart for the First Feed
Interval.
© CANON INC.
Second Printing-June, 1974