Ptx Amplifier Service Check - IBM 5280 Maintenance Information Manual

373
PTX AMPLIFIER SERVICE CHECK
1 . Power off.
DANGER
Capacitor discharge voltage might be present at the
socket when the AC drive motor power cable is
d i scon nected .
2. Disconnect the AC drive motor power cable
m.
3.
Disconnect the PTX cable connector
II
from the
diskette drive control card
IJ .
4. Power on.
5.
Set the multimeter scale to 5 Vdc and connect the
positive probe to
II
(+index).
6. Connect the negative probe of the multimeter to
II
(ground).
7. Check for a voltage level of less than 1 V dc.
52 LED and PTX Assemblies
373
8.
9.
Connect one end of a jumper to
D .
Observe the multimeter and touch the other end of
the jumper to
II
several times. The multimeter
should read 2.5 Vdc or more when
II
is touched.
(A wrong reading can occur the first time
II
is
touched.)
10. (51 TD) Repeat steps 8 and 9 with the jumper on
fJ·
11. Power off.
12. Remove the jumper.
13. Reconnect the PTX cable connector
II
to the
diskette drive control card
IJ .
14. Reconnect the AC drive motor power cable
m.
15. Power on.