Motorola MVME2600 manual Polyswitches Resettable Fuses, Fuse Assignments, Power, Fuse Voltage

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Functional Description

Polyswitches (Resettable Fuses)

The MVME2603/2604 base board draws fused +5V DC, +12V DC, and –12V DC power from the VMEbus backplane through connectors P1 and P2. The 3.3V DC and the core processor voltage power is supplied by the on-board +5Vdc. The following table lists the fuses with the voltages they protect.

Table 3-3. Fuse Assignments

Fuse	Voltage
R28	–12V DC (used on
	MVME761 versions)
R30	+5V DC
R34	+12V DC

I/O Power

The MVME2603/2604 base board furnishes +12V DC and (in MVME761 I/O mode) –12V DC power to the transition module through polyswitches (resettable fuses) R34 and R28 respectively. These voltage sources power the serial port drivers and any LAN transceivers connected to the transition module. Fused +5V DC power is supplied to the base board’s keyboard and mouse connectors through polyswitch R30 and to the 14-pin combined LED-mezzanine/remote-reset connector, J1. The FUS LED (DS5) on the MVME2603/2604 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 +12V DC LAN power, indicating in turn that polyswitch R34 is good. If the Ethernet transceiver fails to operate, check polyswitch R34.

In MVME712M I/O mode, the MVME2603/2604 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 SCSI LED on the

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