Light Emitting Diode (Led) - IBM System/32 Introduction And Maintenance Manual

3.2.23 Light Emitting Diode (LED)
Service Check
1.
2.
Turn power off at the operator control
panel.
Remove the 33FD from the machine (3.2.5).
3. Turn the power on.
4.
5.
Attach the positive probe of VOM to the
LED current test point and the negative
probe to the ground test point on the
file control card located on the 33FD.
Voltage should measure +1.0 Vdc to
+1.6 Vdc.
Turn the power off and install the 33FD
in the machine.
Removal and Replacement
1. Turn power off at the operator control
panel.
2.
Remove the 33FD from the machine
(3.2.5).
3. Remove covers (3.2.8).
4. Remove two mounting screws
II .
5. Remove leads. (Yellow wire goes to
terminal marked Y.)
6. To replace, reverse above procedure.
IOn the old style file control card (2 wide, 3 high), test
points are located randomly on the component side of
the card. On the new style file control card (2 wide,.
2 high), test points are brought out to two rows of pins
labeled TPA and TPB. For the location of other test
points, see 3.2.24.
CAUTION
Before replacing
cover screws, posi-
tion actuator bail,
located on cover,
under pressure
pad arm.
----~
Old Style File Control Card
1
00
Erase Current
+5 Vdc
+24 Vdc
0000
. - - - - - - - - - - + Preamp TP2
+ Write Gate - - f - - - - - -
+
Low Cu rren t --+-----
+
Index
- - - ? -
•
- Head Load
,.------,c=T-,:::.....:>,,.-i------rl-
+
Head Engage
,.--------==+
+
Write Data
----t-MC-1
Phototransistor
0
Current (yellow)I _ _ _ _ _ _
___==i
MC-2
---+MC-3
I
+ Access 1/2
- + - - - - - - - - . •
+ Access 3/0
- / - - - - - _ _ = '
-- 5 V de
- - - t - - - - - - - , \
+
Access 2/3
New Style File Control Card
1
Phototransistor Current
+5Vdc _ _ _ -,.
+
Index
MC-O
•
-i--+---:?c;:-~~ Pream p TP 1
.+:----==--t
G ro u nd
-----fLED Current
' - - - - - - - + Access 0
Ground
33FD Diskette Drive 3-23