Manual 0-2972
4-1
TROUBLESHOOTING
SECTION 4:
TROUBLESHOOTING
4.01 Introduction
This section provides service diagnostics for the CutMas-
ter 51 Power Supply, allowing the Technician to isolate
any faulty subassemblies. Refer to Section 5, Repairs &
Replacement Procedures, for parts replacement instruc-
tions.
Under no circumstances are field repairs to be attempted
on Printed Circuit Boards or other subassemblies of this
unit. Evidence of unauthorized repairs will void the fac-
tory warranty.
NOTE
The troubleshooting contained in this manual is
for the Power Supply only. Troubleshooting other
parts of the system is covered in the manuals for
those products.
4.02 Periodic Inspection & Cleaning
Procedures
WARNING
Disconnect primary power and bleed down the sys-
tem before disassembling the torch, leads, or power
supply.
To clean the unit, open the enclosure per procedure in
section 5.05-A, Cover Removal, and use a vacuum cleaner
to remove any accumulated dirt and dust. The unit
should also be wiped clean. If necessary, solvents for
cleaning electrical apparatus may be used.
Refer to the Appendix for maintenance schedule and pro-
cedures.
4.03 System Theory
A. Logic PC Board Functions
The Logic PC Board controls the timing and sequenc-
ing of the system. It monitors gas pressure and power
supply internal temperatures, and controls the gas flow.
The Logic Board also controls the safety latch circuit.
After the ON/OFF switch is closed on the front panel,
the AC Indicator
turns on.
The GAS indicator
is ON when there is sufficient
gas pressure in the power supply to enable power sup-
ply operation.
NOTE
Minimum gas pressure for power supply operation
is lower than the minimum for torch operation.
When the unit is at “idle” the AC indicator
on
the Front Panel should be ON. When the torch is acti-
vated, the gas begins to flow. After a brief preflow, the
INV ON signal is given, and the DC indicator
on
the Front Panel turns ON.
An open circuit voltage of approximately 230 to 300 vdc
(depending on input power) is produced when the
switching of the IGBTs in the Main PC Board is turned
ON by an INV ON signal from the Logic PC Board. A
circuit on the Logic PC Board monitors the output volt-
age. When the output voltage drops below 60 vdc, indi-
cating a problem exists, the Logic PC Board sends a sig-
nal which turns OFF the INV ON Enable signal. This
happens in less than 50 milliseconds.
When the torch is activated, gas will flow for approxi-
mately two seconds before DC is established (indi-
cated on the front panel). Then the gas shuts off briefly.
The gas flow then starts again and the torch starts a
pilot arc.
When the torch is close to the workpiece, the cutting
arc "transfers" to the work.
The resulting current is sensed by the Current Sense
circuit, resulting in the demand level changing from
pilot current to the main current control setting, and
then the main cutting arc starts. If the torch is removed
from the workpiece while the torch switch is still
pressed, the main arc extinguishes and the pilot arc
automatically restarts.
