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TROUBLESHOOTING & REPAIR
F-52 F-52
INVERTEC STT
TRIGGER CIRCUIT TEST (continued)
FIGURE F.22 – SIMPLIFIED TRIGGER CIRCUIT DIAGRAM
FROM PROTECTION
BOARD OVERVOLTAGE
PWM
OUTPUTS
TO POWER
BOARD
7J6
2J6
11J4
3J4
13J36
5J36
8J33
6J34
9J4
12J4
3J31
6J22
6J4
POWER BOARD CONTROL BOARD
REMOTE
PROTECTION
BOARD
14 AMPHENOL
#301
#305
#503A
#224
#210
#212
#223
#212C
#413
#405
C
D
T1 AUXILIARY
TRANSFORMER
2
4
V
A
C
P
W
M
5J4
TO
POWER
BOARD
2J31
3.5 ohms
3.5 ohms
STT II Only
#379
7. Using the ohmmeter check for continuity (zero
ohms) from plug J31 pin 3 (lead#503A) to plug
J4 pin 6 (lead#210). See Figure F.22,
Simplified Trigger Circuit Diagram.
8. If any of the resistance checks are abnormal-
ly high in steps 5, 6 or 7, check for broken or
loose wires, connections or "open" ther-
mostats. Also check the small inductors on
the Remote Protection Board. See Figure
F.22, Simplified Trigger Circuit Diagram.
ELECTRIC SHOCK can kill.
• With input power ON,
there are high voltages
inside the machine. Do
not reach into the machine
or touch any internal part.
9. Apply the correct input power to the machine
and turn ON.
10. Locate plug J6 on the power PC board. See
Figure F. 15. in the Power Board Test.
11. Carefully check for approximately 1VDC from
plug J6 pin 2 (lead #305)(+) to plug J6 pin 7
(lead #301) (-). If the approximately 1VDC is
present the power PC board and protection
PC board are functioning properly for the trig-
ger circuit to operate. If the correct DC volt-
age is NOT present, perform the Protection
Board Test and the Power Board Test.
12. Test to make sure the T1 auxiliary trans-
former is producing 24VAC. See Figure F.22,
Simplified Trigger Circuit Diagram.
13. If the above tests do not reveal the problem,
the control PC board or associated wiring
may be faulty. See Figure F.22, Simplified
Trigger Circuit Diagram.
WARNING