Led And Ptx Assemblies; Diskette Speed Service Check - IBM 5280 Maintenance Information Manual

LED and PTX Assemblies
367
DISKETTE SPEED SERVICE CHECK
1. Open the diskette locking lever
II.
2. Insert a diskette into the diskette drive.
3. Close the diskette locking lever
m.
4.
5.
6.
7.
Install a jumper from
fJ
(-head load) to
II
(ground)
to activate the head load solenoid.
If you are using an oscilloscope, proceed with step 5.
If you are not using an oscilloscope, go to step 11.
Set up an oscilloscope to the settings shown in
II.
Place the channel 1 probe on
D.
Note: Use a Tektronix! 453,454, or a similar oscilloscope
with x10 probes.
8. Observe an index pulse width of 1.5 milliseconds to
3.0 milliseconds 1J0ccurring every 166.7 ± 4.2
milliseconds
II.
Pulse amplitude should be between
2.4 Vdc and 4.2 Vdc
II.
1
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44 LED and PTX Assemblies
367
9. Remove the jumper installed in step 4.
10. Go to step 1 7.
11. Cut out the correct stroboscope wheel
lID
for your
diskette drive.
12. Power off.
13. Attach the stroboscope wheel
1m
to the diskette
drive spindle pulley
D.
14. Power on.
15. Direct the beam of a fluorescent lamp onto the
stroboscope wheel. (If the diskette speed is correct,
the outer ring of dots on the stroboscope wheel wi II
appear to be moving in a counterclockwise direction
and the inner ring of dots will appear to be moving
in a clockwise direction.)
16. Remove the jumper installed in step 4.
17. Open the diskette locking lever and remove the
diskette.