Powertronix Quasar Service Manual page 99

Service Manual
Figure 7-13 Testing the twin pack SCR
9 volt power
Test lamp
source
ve
+ve ve
+ve
9 volt power source
and switch
To functionally test a twin pack SCR as shown in Figure 7 12 a DC power source and test lamp is re
quired, typically a 9V PP3 battery and 12V bulb.
1.
2.
3.
4.
5.
3x3 UPS
Issue 2 - November 2001
9 volt power
Test lamp
source
ve
+ve
9 volt power source
and switch
Connect the bulb and battery to SCR1 as shown, connect the +ve to the anode (1) and ve
to the cathode (2) terminal.
Using a second power source or link from the battery connect the +ve lead to SCR1 gate
terminal 4 and the ve lead gate terminal 5.
Switch on the SCR by briefly making the gate circuit, use a switch if available.
The SCR will fire and the bulb will light and remain on. The bulb provides a current source
for the SCR and it will continue to fire.
Remove the +ve connection from terminal 1.
The bulb will extinguish an the SCR will switch off.
Repeat the test for SCR2.
+ve
ve
Test Procedures
Twin pack SCR
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