Firepower, a Thermadyne Company FIREPOWER FP-82 - Manual (Page 19)

Manual 0-2871 4-1 SERVICE
SECTION 4:
SERVICE
4.01 Introduction
This section provides service diagnostics for the Fire-
power FP-82 Power Supply, allowing the Technician to
isolate any faulty subassemblies. Refer to Section 5, Re-
pairs & Replacement Procedures, for parts replacement
instructions.
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 Appendix 13 for maintenance schedule and pro-
cedures.
4.03 System Theory
The Firepower FP-82 System is designed for hand opera-
tion using the torch control bulkhead within the power
supply as the interface.
A. Logic PC Board Functions
The Logic PC Board controls the timing and sequenc-
ing of the system. It monitors the pressure and tem-
perature, and controls the gas flow in Run and Set
modes by turning on the plasma solenoid.
After the ON/OFF switch is closed on the front panel,
the AC Indicator blinks for approximately eight sec-
onds then it becomes steady and the Main Contactor
closes.
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. When the preflow time
is over, the INV ON signal is given, and the DC indi-
cator at 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 voltage. When the output voltage drops be-
low 60 vdc, indicating a problem exists, the Logic PC
Board sends a signal which turns OFF the INV ON
Enable signal. This happens in less than 50 millisec-
onds.
When the torch is activated, gas will flow for approxi-
mately two seconds before DC is established (indi-
cated on the front panel). During this time the CD
Enable indicator will come on and sends a logic sig-
nal to the CD Board which fires the spark gap and
initiates the pilot. The CD Enable indicator should go
out immediately if the pilot starts immediately.
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 whatever the main current control is
set at, and then the main cutting arc is initiated. 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.
Indicator Meaning
D20 CD on
D21 Inverter on
D32 Torch Switch On
D37 Drag Circuit on
Firepower FP-82 Logic Board Indicators