Led Replacement; Ptx Amplifier Service Check - IBM 3274 51C Maintenance Information

E.3.6.4 LED Replacement
See Figure E-38.
1. Reinstall the LED cable, the LED assembly,
e '
and the mounting screw,
CD '
on the diskette
guide,
O.
2. Reconnect the LED connector,
e '
to the control
card.
E.3.6.5 PTX Amplifier Service Check
See Figure E-39.
" Diskette
Guide
Figure E-38. LED Removal and Replacement
1. Power down.
I
DANGER
Voltage is still present at the socket when the
power cable is disconnected.
2. Disconnect the ac drive motor power cable, " .
3. Remove the PTX connector,
G ,
from the control
card.
4. Power up.
5. Connect the positive probe,
G '
of a multimeter,
CD '
(15 Vdc scale) to the index test pin (TPE03)
on the control card.
6. Connect the negative probe,
G '
of the multimeter
of TPF 01 (ground).
7. Check the multimeter,
E) ,
for a reading of less
than 1 Vdc.
r
~
e
LED Assembly
v--~_"
' /
~
GLED/
Mounting Screw
Appendix E. IBM 31SD Diskette Drive Maintenance E-Sl