Service Manual
Test Procedures
7 - 24
3x3 UPS
Issue 2 - November 2001
Single SCR and Diode Pack Replacement. (S7 S8)
1.
Power down the UPS and carry out the DC bus discharge routine.
2.
Gain access to the UPS power section by removing the top and side covers.
3.
To gain access to the SCR's disconnect and remove the Input Filter PCB Part NºOSDE0079.
Follow the procedure on
page 7Ć38
.
SCR S7
4.
Disconnect the Red and Black gate drive Connectors from 4Q1 (red) and 5K1 (black).
5.
Disconnect the Battery negative bus bar from SCR terminal 2.
6.
Disconnect Fuse F4 bus bar from SCR terminal 1.
7.
Disconnect black leads from R2 to SCR terminal 1 and 2.
8.
Remove red leads from SCR terminal 1 and 2 which connect to the fast on connectors F12
(SCR 1) and F11 (SCR 2) on the Inverter driver/feedback PCB.
Note: There is no connection to SCR terminal 3.
9.
Remove the two SCR Allen retaining screws from the SCR and lift from the Heatsink.
Note: There is a deĆcoupling capacitor linking the heatsink from SCR mounting
screw to the neutral bus bar.
SCR S8
10. Disconnect the bve cable from SCR terminal 3.
11. Disconnect red leads from R1 to SCR terminal 1 and 2.
12. Remove fuse F1 bus bar from SCR terminal 2.
13. Remove the input bridge bus bar from SCR terminal 1.
14. Remove red leads from SCR terminal 1 and 2 which connect to the fast on connectors F13
(SCR 1) and F14 (SCR 2) on the Inverter driver/feedback PCB.
15. Carry out the following functional test on each SCR and replace if required.
SCR fitting is the reverse of the removal procedure.
Figure 7-14 Single SCR Test.
9 volt power source
and switch
+ve
ćve
Test lamp
9 volt power
source
+ve
ćve
Single SCR & Diode pack