IBM Selectric - Page 178

DOG CLUTCH PAWL AND RATCHET CHECK
The distance in time between the teeth of the dog clutch rat-
chet is 14 ms. Normal operational cycles will vary in time
depending. on where the clutch pawl enters the clu·tch ratchet.
This variation, however, should never exceed 14 ms. Any
more
vari ati on wou Id i ndi cate worn paw Is or ratchets.
Figure 30.6
Scope: Across resistor in series with magnet coi I.
Set OlSA to single cycle. Operate printer in short burst
with the start pushbutton. Observe variati on of pu Ise length.
The example shows a variation in pulse length of about 12 ms
for the eight printer cyc les recorded.
LOWER CASE MAGNET
Figure
30.7
Scope:
Time Base:
Across Resistor in Series with
Magnet Coi I
10 ms/cm
Vert Amp:
2
volts/cm
Sync:
+ Int
Time from start of pi ck to feedback
Magnet seal time
C4 makes at 35°
Total Mechanical Delay
6.0 ms
12 . .1> ms
25.0 ms
18.5 ms
6.5 ms
5-34
U.C. MAGNET
Figure 30.8
Scope:
Across Resistor in Series with MagnetCoi I
Time Base:
Vert Amp:
Sync:
10 ms/cm
2
volts/cm
+ Int
Time from start of pick to feedback
Magnet seal time
C3 makes at 35°
Total Mechanical Delay
MACHINE SPEED CHECK
Figure 30.9
Machine Cvcle = 65 ms
Scope:
C2 N/O Contact Point
Ref:
Power
Supply Common
Time Base: 10 ms/cm
10.0 ms
12.5 ms
28.0 ms
22.5 ms
5.5 ms
Vert Amp:
2
volts/division (with lOx attenuated probe)
Rise of
C2 N/O to next C2 N/O = One Machine Cycle