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28 February 1989
3.12 EXPOSURE LAMP CONTROL CIRCUIT
AC power
Zero cross
Trigger pulse
Lamp power
Feedback signal
The I/O control board sends lamp trigger pulses to the ac drive board from
CN304-A19. PC401 activates TRC401, which provides ac power to the ex-
posure lamp at the trailing edge of each trigger pulse.
The voltage applied to the exposure lamp is also provided to the feedback cir-
cuit. The feedback circuit steps down (T401), rectifies (DB405), and smoothes
(zener diodes and capacitors) the lamp voltage. The CPU monitors the lowest
point of the smoothed wave (feedback signal). The lowest point of this signal
is directly proportional to the actual lamp voltage.
In case of overheating, the thermoswitch opens at 130°C and removes ac
power to the exposure lamp.
2-21
Summary of Contents for FT4460
Page 1: ...RICOH R I C O H F T 4 4 6 0 RICOH COMPANY LTD...
Page 19: ...SECTION 1 OVERALL M A C H I N E INFORMATION...
Page 29: ...28 February 1989 3 COPY PROCESSES AROUND THE DRUM...
Page 30: ...28 February 1989 4 FUNCTIONAL OPERATION 1 10...
Page 38: ...28 February 1989 7 MECHANICAL COMPONENT LAYOUT...
Page 49: ...SECTION 2 DETAILED SECTION D E S C R I P T I O N S...
Page 136: ...Section 2 Timing Chart following page...
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Page 138: ...S E C T I O N 3...
Page 158: ...SERVICE T A B L E S...
Page 212: ...REPLACEMENT AND...
Page 334: ...SECTION 12...
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