HP HP-97 - Page 115

HP-97 Component-Level Maintenance
Table 4-15. Card-Reader Troubleshooting Procedure (Continued)
STEP ACTION
19.
Remove the motor from the card
reader. Apply moly-disulphide (Moly-
kote G, or equivalent) to the
thrust bearing at the end of
the worm gear.
Check for:
0 bent worm gear;
o bad couplers;
0 bad drive roller and gear;
o bad motor bearings;
Replace as required.
20. Go to step 20.
Reinstall the motor in the
card reader. Return to step 5.
21.
Monitor the head signals
across HA and HB with an
oscilloscope set to 0.05
V/div vertical gain and
1 msec sweep, while read-
ing a prerecorded card. If good signals appear at both
HA and HB, replace U1. Return to
step 14.
If good signals do not appear
at both HA and HB, replace the
Good head. Then return to step 2.
Signal
Bad
Signal
4-UT/4-L8