Environmental Characteristics; Safety; Personal Safety; Machine Safety - IBM 3274 51C Maintenance Information

, E.1.2.3 Environmental Characteristics
IBM diskette drives can be operated or stored in the follow-
ing temperature and humidity ranges, shown in Figure E-6.
E.1.2,4 Functional Characteristics
The format of the data on a diskette is changed when the
number of bytes written in a sector is changed. Diskettes
are used with the formats shown in Figure E-7.
• The maximum number of formatted data bytes per
diskette is shown in Figure E-8.
• Data rate: 250,000 bits (31,250 bytes) per second (FM).
• Cylinder-to-cylinder seek time: 5 ms, plus 35 ms for the
head/carriage assembly to stop. (The total seek time is
the number of cylinders the heads moved across multi-
plied by 5 ms, plus 35 ms.)
• Tracks per diskette side: 77 (cylinder 00 is the label
cylinder; cylinders 01 through 74 are for data; cylinders
75 and 76 are reserved as alternative cylinders).
E.1.3 Safety
E.1.3.1 Personal Safety
The system or device supplies ac and dc power. Ac voltages
are present on the drive motor connector and capacitor
terminals in the diskette drive when the drive motor is
turning.
Motor and solenoid cases become hot after continuous
use; let the parts cool before servicing them.
The Danger and Caution notices throughout this appen-
dix are personal safety precautions.
E.1.3.2 Machine Safety
Diskette drives can be damaged if they are not operated or
serviced correctly. The Warning notices in this qppendix
are machine safety precautions.
Do not use IBM cleaning fluid or other cleaning fluids
near plastic parts.
Never use damaged diskettes in a diskette drive. Disk-
ettes that are physically damaged (creased or bent) or con-
taminated (by pencil marks, finger marks, or cleaning fluid)
can cause data errors, equipment errors, or head damage.
E-8
Temperature
Celsius
Fahrenheit
Operate
10° to 40.6° 50° to 105°
(Powered On)
Store
10° to 51.7° 50° to 125°
[(Powered Off)
Figure E-6. Environmental Characteristics
FM
I
- 26 - 128 bytes per sector
I
-15 - 256 bytes per sector
I
- 8 - 512 bytes per sector
I
Figure E-7. Data Formats
Diskette 1
128 Bytes
246,272
1
per Sector
256 Bytes
284,160
per Sector
512 Bytes·
303,104
per Sector.
Relative
Humidity
8% to 80%
8% to 80%
1
The total number of data bytes that can be stored on the
diskette. The Basic Data Exchange Standards for exchang-
ing information from one system to another using disk-
ette 1 are:
• Use 128 bytes per sector.
• Do not use track 74.
• Use 26 sectors per track.
The total number of usable data bytes then becomes
242944.
Figure E-S. Maximum Number of Formatted Data Bytes