inverter regulation at low-line
full load conditions.
Inverter randomly blows input fuse
Defective (shorted) SCR A1Q2 or
Measure the resistance across re-
(A1F1) or trips circuit breaker
improper drive to SCR A1Q2
sistor (A1R6) (fig. 6-1). If it is
A1CB1 upon unit start-up. Once
gate (1973 model).
less than one ohm, SCR (A1Q2)
the inverter is operating, unit
(fig. 6-1) is probably shorted and
operation appears normal.
should be replaced. If the resist-
ance is one ohm, problem is prob-
ably the drive to SCR (A1Q2)
6-8d for troubleshooting proce-
Inverter will not operate and input
Defective inverted circuit drive
Replace inverter drive circuit A1A2
fuse (A1F1) is not blown and cir-
(FO-3). Refer to paragraphs 6-8
cuit breaker A1CB1 does not trip.
and 6-9 for repair.
No output voltage from inverter
Defective inverter circuit drive.
Use a multimeter to determine if a
drive circuit board at connector
bypass thyristor drive greater
A1A2J1 (pin 1), coupled with a
than +1 vdc is evident at con-
burned out resistor (A1A6).
nector A1A2J1 (FO-3), pin 1
(inverter drive circuit). If a by-
pass SCR drive is not present,
replace the inverter circuit drive
A1A2 (FO-3) in its entirety.
Refer to paragraphs 6-9 and
6-10 to troubleshoot and repair.
DC circuit breaker A1CB1 trips for
Adjustment of upper or lower limit
Perform a high or low voltage fault
no apparent reason.
of DC circuit breaker A1CB1
adjustment per paragraph 6-23
trip points is required to achieve
or 6-24, respectively.
proper unit operation.
The inverter drops out of regulation
Defective SCR drive A1A2Q16.
Determine the voltage drop across
at light loads. Upon subsequent
resistor (A1R6) (fig. 6-1) on the
loading the units starts to smoke
inverter. This value should be
and becomes very hot (1973
less than -1vdc. Measure the
voltage collector to emitter of
transistor (A1A2Q16) (FO-3)
on the p.c. Board. This reading
should be +9 to +10 vdc. If it
is zero, check the voltage from
base to emitter. This reading
should be less than 0.7 VDC. If
it is at 0.7 VDC, replace defective
transistor (A1A2Q16) (FO-3).
Circuit breaker A1CB1 trips on ini-
Blown input fuse A1F1.
Replace input fuse (A1F1) (fig.
tial turn on (1973 model).
6-1). Opening cabinet door with
unit operating may cause A1F1
No output but inverter is running
a. Open A1CB2.
a. If AC VOLTAGE meter A1M4
(1974 model only).
indicates 120 VAC and there is
no output, check/reset A1CB2.
Replace faulty components.
b. Shorted A1C3 or broken wire be-
b. If no voltage is indicated on AC
tween A1T1 and system output.
VOLTAGE meter A1M4, discon-
nect one side of A1C3 and check
for a short with a multimeter.
If there is no short, check for
an open in meter A1M4 or broken
wires. A1C3 should be at 660
vac during normal operation. Re-
place faulty components.