I/O Power; Table 5-4. Fuse Assignments - Motorola MVME2700 Series Installation And Use Manual

Polyswitches (Resettable Fuses)
The MVME2700 base board draws fused +5Vdc, +12Vdc, and
–12Vdc power from the VMEbus backplane through connectors P1 and
P2. The 3.3Vdc and 2.5Vdc power is derived on-board from the +5Vdc.
The following table lists the fuses with the voltages they protect.

I/O Power

The MVME2700 base board furnishes +12Vdc and (in MVME761 I/O
versions) –12Vdc power to the transition module through polyswitches
(resettable fuses) F2 and F3 respectively. These voltage sources power the
serial port drivers and any LAN transceivers connected to the transition
module. Fused +5Vdc power is supplied through polyswitch F1to the base
board's keyboard and mouse connectors and to the 14-pin combined LED-
mezzanine/remote-reset connector, J1. The
MVME2700 front panel illuminates when all three voltages are available.
In MVME712M I/O mode, the yellow DS1 LED on the MVME712M also
signals the availability of +12Vdc LAN power, indicating in turn that
polyswitch F2 is good. If the Ethernet transceiver fails to operate, check
polyswitch F2.
In MVME712M I/O mode, the MVME2700 supplies SCSI terminator
power through a 1A fuse (F1) located on the P2 adapter board. If the fuse
is blown, the SCSI device(s) may function erratically or not at all. With the
P2 adapter board cabled to a transition module and with an SCSI bus
connected to the transition module, the green
illuminates when SCSI terminator power is available. If the
the transition module flickers during SCSI bus operation, check fuse F1 on
the P2 adapter board.
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Table 5-4. Fuse Assignments

Fuse Voltage
F1 +5Vdc
F2 +12Vdc
F3 –12Vdc (used on
MVME761 versions)
Block Diagram
LED (DS5) on the
FUS
LED on the module
SCSI
LED on
SCSI
5
5-21