Toshiba 1550, Руководство по обслуживанию

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1550/1560 OPTICAL 7 - 20 Mar. 1998 © TOSHIBA
The exposure control circuit has the following two functions:
A
Manual exposure mode .................. Impresses a constant lamp voltage corresponding to the
setting by the UP/DOWN keys on the exposure lamp.
B
Automatic exposure mode ............. The quantity of light reflected by the surface of the original,
which varies according to its lightness and darkness, is
detected by the automatic exposure sensor circuit, and the
voltage impressed on the exposure lamp is varied accord-
ingly; a high lamp voltage being impressed when the origi-
nal is dark and a low lamp voltage when it is light.
(2) Function of lamp regulator
A typical characteristic curve is shown below. By means of a phase-angle control system, it is
controlled so that a lamp voltage corresponding to EXP-PWM pulse duty ratio input is generated
even when some fluctuation occurs in the AC input voltage.
PWM pulse duty ratio
184, 92 V approx.
92, 46 V approx.
Lamp voltage
Range of actual use
Range of actual use
200 V series
100 V series
Limiter voltage (90V)
[Characteristics of the curve of the lamp regulator]
40 V% 90 V%