TM 11-6625-2965-14&P
Option 11, Overvoltage Protection “Crowbar”
DESCRIPTION:
This option is installed in DC Power Supplies, 6200B, 6201B, 6202B, 6203B, 6204B, and 6206B, and
tested at the factory. It consists of a printed circuit board,
screwdriver-type front panel potentiometer,
and six wires that are soldered to the main power supply board.
The crowbar monitors the output voltage of the power supply and fires an SCR that effectively shorts
the output when it exceeds the preset trip voltage.
The trip voltage is determined by the setting of the
CROWBAR ADJUST control on the front panel.
The trip voltage range is as follows:
Model
6200B 6201B
6202B 6203B
6204B
6205B
6206B
Trip Voltage Range
2.5-44V
2.5-23V
2.5-44V 2.5-10V 2.5-44V
2.5-44V 2.5-65V
To prevent transients from falsely tripping the crowbar, the trip voltage must be set higher than the
power supply output voltage by the following margin: 4% of the output voltage plus 2V. The margin repre-
sents the minimum crowbar trip setting for a given output voItage;
the trip voltage can always be set higher
than this margin.
OPERATION:
1. Turn the CROWBAR ADJUST fully clockwise to set the trip voltage to maximum.
2.
Set the power supply VOLTAGE control for the desired crowbar trip voltage. To prevent false crow-
bar tripping, the trip voltage should exceed the desired output voltage by the following amount: 4% of the
output voltage plus 2V.
3. Slowly turn the CROWBAR ADJUST ccw until the crowbar trips, output goes to 0V or a small posi-
tive voltage.
4. The crowbar will remain activated and the output shorted until the supply is turned off. To reset
the crowbar, turn the supply off, then on.
5. If the CROWBAR must be completely disabled, remove the lead attached to the CROWBAR ADJUST
potentiometer R5.
D-2
