Motorola SG 2000 operation manual Illustrates the location of the LO-HIjumper

3 - 6 B e n c h S e t u p

Note that no damage results if the jumper is not changed. In a 90 Vac system, changing the jumper ensures that the dc supply does not turn on until the proper input voltage level is reached. This prevents excessive loading of the cable plant power supply during turn-on after a power-off situation.

Figure 3-5 illustrates the location of the LO-HIjumper:

F i g u r e 3 - 5

S G 2 - P S 2 p o w e r s u p p l y

SG2-PS2

NO USER SERVICEABLE PARTS INSIDE				ASSEMBLED IN MEXICO
CAUTION					24V	5V
VOLTAGE S IN EXCESS OF
300 VOLTS A R E PR ESENT
U ND ER COVE R A ND M AY
B E PR ESENT A FT ER POW ER			ADJ
IS R EMOVED
SEE INSTALLATION MANUAL FOR SERVICE	LO	HI			TEST	TEST
				POINT		POINT

A second, optional dc power supply located in the lid of the SG 2000, offers full redundancy. Both power supplies are on-line continuously and share the current load. In the event one supply fails, the other assumes the entire load with no disruption of service. Each dc supply can deliver 4.3 A at +24 V and 0.69 A at +5 V. Test points are provided for 24 Vdc and 5 Vdc supplies. Green LEDs— two on each power supply and one on the RF chassis—indicate the overall health of the nodes dc power bus. The power supply is factory calibrated for 24 V and should not need output voltage adjustment. Power supply adjustment R51 is available but should be used only by qualified personnel. When dual supplies are used, the supply with the lower output voltage sets the output voltage of both supplies. Adjusting R51 on the other supply appears to have no visible effect. However, if the “leading” supply fails, the misadjusted supply undergoes a sudden, large voltage change. Figure 3-5 illustrates the location of R51 (ADJ).

The ac input from the feederline to the power supply must be between 44 V and 90 Vrms with a line frequency of 50 Hz or 60 Hz. The wave shape of the input voltage must be quasi-squarewave. The power supply features a self-protection attribute that shuts it down for instantaneous line voltages between 112-142 Vrms. A precision output regulator protects against overcurrent and short circuits, thus providing a precise output voltage.

By selectively positioning a jumper (JP1) on the SG 2000 lid motherboard (LIDB), the power supply can be configured to conform to different power requirements. Figure 3-1 illustrates the location of jumper JP1 and Figure 3-3 illustrates the schematic.

The following subsections explain the powering options.

S G 2 0 0 0 I n s t a l l a t i o n a n d O p e r a t i o n M a n u a l