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TROUBLESHOOTING & REPAIR
F-62 F-62
INVERTEC STT
SWITCH BOARD REPLACEMENT (continued)
TEST AFTER REPAIR OF SWITCH
BOARDS AND/OR CAPACITORS
The following test must be performed after the
switch boards and/or the capacitors have been
replaced.
NOTE: Always make sure that switch boards are
changed in matched pairs. Never mix an old style
(different part number) switch board with a new
style (new part number).
TEST PROCEDURE
1. Turn main power OFF.
2. Perform Input Filter Capacitor Discharge
Procedure. See the Maintenance section.
ELECTRIC SHOCK can kill.
• Before continuing with the
test procedure, perform
the capacitor discharge
procedure to avoid electric
shock.
3. Connect a shorting conductor across termi-
nals 14 and 53 of the protection PC board.
See Figure F.29.
4. Set an ANALOG ohmmeter to X1000 range
and place the probes on terminals 9 (+) and
12 (–) of one switch board. The meter will
show the capacitors charging up and may
take a minute or so to stabilize. The final
meter reading should not exceed 8600 ohms
(8.6 on the scale).
5. Test the other switch board the same way.
NOTE: Repeat the Input Filter Capacitor
Discharge Procedure.
6. Remove the shorting conductor set up in step
3.
7. Replace 20 amp fuses with 5-amp fuses in
the input supply fuse holders.
NOTE: These fuses should be installed to pro-
tect against excessive current flow caused by a
short circuit during the procedure.
WARNING
FIGURE F.29 — SHORTING TERMINALS 14 AND 53 OF PROTECTION BOARD
L7915-[ ]
PROTECTION
53
14
JUMPER TERMINALS