MEASUREMENTS - Starting Lamp Voltage
TYPICAL TWO-LAMP RS BALLAST
52 MAINTENANCE & REPAIR
WHITE
BLACK
BALLAST
Y-1
Y-2
R
B
Starting Voltage
TYPICAL TWO-LAMP RS BALLAST
The largest percentage of light ballast used today are of the two-lamp rapid start type. In order
to read starting or open circuit voltage, as it is often called, remove both lamps from their
sockets. The high voltage (OVC) which starts and operated the lamp is always between the
“R” and “B” sockets. The two lamps are in series between these sockets. The Y-1 and Y-2
connections provide cathode heat, and serve to connect the lamp ends together. Because the
leads between Y-1 and Y-2 are connected together by jumper leads, they are always wired to
sockets at one end of the fixture. Therefore, the “R” and “B” sockets are always at the other
end of the fixture. This means that in order to measure the voltage which starts the lamps
(OVC), the meter probes must be placed in the sockets at one end of the fixture. The Y-1 and
Y- 2 end of the fixture will read zero while the “R” and “B” end of the indoor ballast should read
as follows:
Lamp Type
F40
F30
Min. RMS
Voltage
256
215
HO
48"
72"
96"
Min. RMS
Voltage
256
395
465
1500 MA.
48"
72"
96"
Min. RMS
Voltage
250
350
470
Dipping Cabinet 1298.02 2/3/03 1:15 PM Page 54
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