ESAB EPP-400 Manuel D'instructions page 297

section 6
problem
Works OK at 250A or less- Over
current – Faulty Right Side
Power Supply turns off prema-
turely in the middle of the cut.
problem
Output current is unstable and
drifts above or below the set-
ting.
possible cause
Loose or unplugged connector at Right PWM
/ Drive PCB (PCB3)
Faulty Right PWM / Drive PCB
Check voltage between P5-1 and P5-2 at the
right PWM / Drive PCB (PCB3). Should be 20V
AC. Between P5-1 and P5-3 should be 40V AC.
If not the control transformer (T7) is faulty.
"Contactor On" signal is removed from unit.
Momentary loss of primary input power.
Faulty condition, indicated by illumination
of the fault lamp.
Faulty condition, indicated by the illumination
of the power reset fault lamp.
Current setting too low.
Remote current signal removed during cut.
possible cause
Place the PANEL / REMOTE switch in the "PANEL"
position. Adjust current control pot. If current
no longer drifts, the remote current control
signal is faulty.
Select "PANEL" on the PANEL / REMOTE switch
and adjust the current control pot. The cur-
rent still drifts, measure the current reference
signal at TB1-4 (+) and TB1-5 (-). If the signal
drifts, the current control pot is faulty. If the
signal does not drift, the Control PCB (PCB1)
is faulty.
297
troubleshootinG
action
Secure connector
Replace right PWM / Drive PCB P/N
38030
Replace control transformer T7
Power source is OK. Trouble shoot pro-
cess controller.
Restore and maintain input voltage
within ±10% of nominal.
Remove control PCB (PCB1) access panel
to determine the fault causing the shut-
down. Refer to fault light illumination
section.
Remove control PCB (PCB1) access panel
to determine the fault causing the shut-
down. Refer to fault light illumination
section.
Increase current setting
Fix remote current signal
action
Fix the remote current control signal to
operate the PANEL / REMOTE switch in
the "PANEL" position.
Replace the current control pot.
Replace the control PCB (PCB1) P/N
0558038287