Philips PM32671 Service Manual page 36

2-20
I n the triggered mode, the signal path that starts the MTB directly after the hold-off period (in auto free-run
mode) is interrupted by an H level on NAND gate D209-2. This interrupted signal path is via D211 (3,4,5,6)
and D209 (2,3,1).
The finish of the MTB sweep a t the start of the hold-off period is identical to the situation described for AUTO
mode. A t the start of the hold-off period, input pin 2 of NAND gate 0 2 1 1 becomes L. As inputs 1 and 13 are
both H, output pin 12 becomes H. This produces via NOR gate D209 (8,9,10) a logic L that is applied to reset
input (13) of flip-flop D212. Consequently, the flip-flop switches over and the MTB stops.
2
1
13
11
9
Only by forcing the
re-trigger the time-base. Reset i s achieved if the SINGLE/RESET pushbutton is depressed, t o give an L level t o
SR
input 10 of the flip-flop. However, the time-base can only be triggered if the SINGLE/RESET pushbutton
i s in the normal position. If it i s depressed, the reset input (pin 13) of flip-flop D212 remains
D214 (9,10,8) and D209 (8.9,lO).
I n the SINGLE mode, the signal path that starts the time-base directly after the hold-off period (in AUTO
free-run mode) is interrupted by an H level on D209-2. This interrupted signal path is D211 (3,4,5,6) and
D209 (2,3,1).
Input pin 1 of SR flipflop D211 is permanently
gives an L level on reset input pin 13 of D212, which inhibits the start of the time-base in this mode.
The not triggered indicator, LED B I , i s supplied with current from the current source V1512 on the FINAL
AMPLIFIER UNIT A5 via X202-7.
I f the time-base is running, flip-flop output D212-8 is L, this level being applied via diode V252 and via
When trigger pulses occur with a time interval of 100 ms or less, pin 6 of one-shot multivibrator D213 is
permanently a t logic L. This L output is fed via diode V251 t o the anode of B1 to switch it off.
I n the SINGLE mode, the output 8 of flip-flop D211 i s L from the start of the hold-off period until the
moment when the SlNGLE/RESET pushbutton is depressed. This L level is applied via diode V249 t o the
anode of B1 t o hold it off.
LEVEL
only L i n E X T X D E F L
only L in AUTO and TRIG 8
I
SR
flip-flop back t o the reset condition (output 12
a t
OUTPUTS
I I
I
12
I
I
I
L, output 8 a t H) i s it possible to
a t
level L. Consequently, output D211-I2 is H. This H level
L
H
a t level L via