IBM System/34 Maintenance Manual page 385

27-805
DRIVER BOARD OUTPUT TO THE
CARRIAGE BED STEPPER
MOTOR SERVICE CHECK
1. Open the front left side cover.
2.
3.
4.
5.
Loosen the two front safety shield screws and
remove the two rear safety shield screws and the
safety shield.
Set Power to I (operator panel).
Connect the negative probe of a multimeter to test
pin THP-1
G
(ground). With the positive probe
measure the voltage at point. on diodes 11 and
13 (3.5 Vdc to 4.7 Vdc).
Access the read/write head carriage to single step
the carriage bed stepper motor as follows: (Do not
access the read/write head carriage more than
one cylinder at a time.)
Set the Mode Selector switch to the Proc Run
position (CE panel).
Set the Address/Data switches to FSOO (CE
panel).
Set all CE panel switches to their down
position.
Press the Load switch (operator panel).
Select the exerciser option.
Select the diskette option.
Select the stepper motor step test option and
the read/write head carriage will move to
cylinder
40.
Install a jumper from THP-4
0
(single step
bed) to TH P-1
e
(ground).
Use the advance motor option of the stepper
motor test to single step the bed stepper
motor.
Note: This procedure uses the read/write head carriage
circuits to move the carriage bed stepper motor.
Therefore, be careful to prevent damaging the
read/write head carriage control circuits as well as the
read/write carriage assembly.
100 27-S05
DANGER
Parts of the driver board become hot after continuous
use.
6. For the old style picker, probe test pin TPB-24
e
(-bed motor) for a down level. If the output is not
at the desired level, perform the control card
output check (see paragraph 27 -S50).
For the new style picker, probe test pin TPB-23
e
(-bed motor) for a down level. If the output is not
at the desired level, perform the control card
output check (see paragraph 27 -S50).
7. For the old style picker, connect the negative
probe of a multimeter to test pin TPA-12
G
(ground). With the positive probe measure the
voltage at point
0
on diodes 010, 011, 012, and
013. The voltages should compare with those
shown on the chart when single stepping. The
measured not active level voltage (measured when
single stepping) should be higher than the detent
voltage measured in step 4.
S.
9.
For the new style picker, connect the negative
probe of a multimeter to test pin TPA-13
G
(ground). With the positive probe measure the
voltage at point
0
on diodes 010, 011, 012, and
013. The voltages should compare with those
shown on the chart when single stepping. The
measured not active level voltage (measured when
single stepping) should be higher than the detent
voltage measured in step 4.
Remove the jumper.
Reinstall the safety shield using the four screws.
'-._.--
C~