KEPCO RA 76 User Manual
Page 4
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228-1439 REV 1
6/20/03
c. Calculate the value (in ohms) of resistors A1R1 through A1R3, with respect to the power supply voltage (V
n
)
and the operating characteristics of the LED (DS1 through DS3). Refer to Table 2 for resistor values and
Kepco part numbers associated with standard Kepco power supply output voltages.
where V
n
= voltage across resistor/LED network (power supply output voltage)
where V
F
= forward voltage across LED (approximately 2V)
where I
F
= forward current across LED (approximately 20mA)
The following is an example for a resistor value associated with a 5 volt power supply:
resistor value (in ohms) Rn =
Calculate the power rating (in watts) as follows:
* use nearest larger standard size (1/4 or 1/2 Watt).
d. Position and solder resistor in place (see Figure 5).
e. Reassemble PCB assembly (see Figure 5) and reattach front panel to chassis using five screws.
2. Install the FAW power supplies in the Rack Adapter (see Figure 7) using four 4-40 x 3/8 ST. FLSO screws (sup-
plied).
3. Wire the Rack Adapter as needed. Schematic Diagram Figure 6 is provided as a guide showing a typical installa-
tion of three FAW power supplies. Be sure to connect resistor RS1 (supplied).
4. Replace top cover and secure with screws removed during disassembly.
5. Install the line cord (supplied) at connector J1 at the rear panel.
6. Install the unit in the rack and secure using suitable mounting hardware (not supplied).
TABLE 2. RA 75/RA 76 RACK ADAPTER LEDS, RESISTOR SELECTION
OUTPUT VOLTAGE
RESISTOR
KEPCO P/N
5V
150
Ω
, 10%
,
1/2W
115-0543
12V
560
Ω
, 5%,
1/2W
115-0888
15V
750
Ω
, 5%, 1W
115-2438
24V
1.1K
Ω
, 5%, 1W
115-0545
28V
1.5K
Ω
, 10%, 1W
115-0664
48V
2.7K
Ω
, 10%, 2W
115-2465
V
n
V
F
!
I
F
------------------
5V 2V
!
20mA
--------------------
150 ohms
"
"
"
2 I
F
V
n
V
F
!
(
)
Ч
Ч
2 20mA
5V 2V
!
(
)
Ч
Ч
"
0.12W
*
"