Key Control Led Lighting Up Circuit - Kenwood LVD-K9200 Service Manual

LVD-K9200
9. KEY CONTROL LED Lighting Up Circuit (X25-5410)
A. When all LED's are turned off (In the NORMAL
mode)
Since the pins 66 and 69 are at H, the outputs of 5/6
and 6/6 of the IC303 are set to L, and Q311 !s turned
off. Accordingly, all the LED's are turned off.
B. When "b " is lighted up
Since the pin 66 is at H and 69 is at L, the output of
the 1C303 (5/6) is at H and that of (6/6) is at L, and Q311
is turned off. Accordingly, D307 and D306 which re-
ceive a forward bias are lighted up.
(66 pin)
Sub p-com O
(69 pin)
1C303 (5/6)
1C303 (6/6)
C. When "#" is lighted up
Since the pin 66 is at L and 69 is at H, the output of
the 1C303 (5/6) is at L and that of (6/6) is at H, and Q311
is turned off. Accordingly, D304 and D305 which re-
ceive a forward bias are lighted up.
D. When "4" is lighted up :
Since pins 66 and 69 are at L, the outputs of 5/6 and
6/6 of the 1C303 are at H, and 0311 is turned on. Al-
though 0304 and D307 receive a forward bias, they are
not lighted up, since D308 is lighted up by a lower volt-
age. As the result, only D308 is lighted up.
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