Read Data - IBM 3274 51C Maintenance Information

Data
~I
J.-
2-8it Pad
ffF---~ILA.-1
__
D_a_t_a_F_ie_ld_~r9'-----If~~_~_~...a1
Write Gate
Erase Gate
°1
(ff----~IO
__
:f~---Ie
Figure E-15. Record Update - Write Operation
E.2.4.3 Read Data
Read data is the FM encoded read head signal that can be
observed at TPAMP1 and TPAMP2. See Figures E-16
through E-20.
Typical measurements for FM encoding are:
125 kHz: 120 to 300 mV (all O's)
250 kHz: 100 to 250 mV (all 1 's)
The voltage is higher at the outer tracks because of the
higher track speeds and lower bit density.
READ DATA: MFM ENCODED (51TD ONLY)
Read Head Signal at TPAMP1 and TPAMP2
0.05 V/cm
0.05
V/cm
........ - .......... 2.0ms/cm
- -
..........
- -
200.0 }Js/cm
Figure E-16. Read Data Signals
-
SCOPE SETUP
Note:
Use Tektronix 453, 454, or similar
oscilloscope with x 10 probes.
Channel A sweep mode Normal
Channel A level +
Channel A coupling
DC
Channel A slope +
Channel A source Ex ternal
Trigger Normal
Mode Add
Channell voltsl division
5 mV/cm
Channel 2 volts/division
5 mV/cm
Channell input
AC
Channel 2 input
AC
Invert Pull out
Times per
di~ision 2 ms/cm
Connect channel 1 to
TPAMPl
Connect channel 2 to
TPAMP2
Connect trigger to +Index test pin
Observe:
The amplitude of the read signal
should be between 6.5 to 560 mV.
Appendix E. IBM 31S0 Diskette Drive Maintenance E-19