IBM 7133 D40, Service Manual

Page: 59 / 306

Power Sequencing
The 7133 Models D40 and T40 have no power sequencing. All the disk drive modules
start their power sequence when the input voltages are inside the specified limits. Their
motors are started under control of the SSA attachments in the using system. To
prevent the need for excessive electrical current, the disk drive module motors are not
all started together. Up to eight disk drive modules can be started together. At least 10
seconds must elapse before the next group of motors is started. Normally, all the disk
drive module motors are running in less than 30 seconds from the time the 7133 is
switched on.
Disk Drive Acclimation
If you bring a disk drive module into the operating environment from an environment
where the temperature is outside the specified operating range (see Environment),
allow the disk drive module time to acclimate to the operating environment. Remove the
disk drive module from any shipping packaging, but leave it in its sealed plastic bag (if
present) to prevent condensation forming.
SSA Bypass Cards
The four bypass cards that are at the back of the 7133 Models D40 and T40 provide
the connections between the external SSA cables and the disk drive module strings.
Each bypass card has two external SSA connectors. Through these connectors, the
bypass cards and, therefore, the disk drive module strings, can be connected to each
other or to the using system.
The bypass cards can be jumpered for the following modes:
v
Automatic mode
v
Forced Inline mode
You can change the mode by changing the position of the jumpers (see “Bypass Card
Jumpers” on page 45).
When a bypass card is in Automatic mode, you can select additional modes by using
the 7133 service aids (see “7133 Models D40 and T40 Service Aids” on page 62) or the
Command Line tools (see “Command Line Tools” on page 266). The additional modes
are:
v
Forced Inline mode
v
Forced Bypass mode
v
Forced Open mode
Note: The cards need not all be in the same mode.
Chapter 1. Reference Information
41