Thermadyne Thermal Dynamics PAK MASTER 50XL, Service Manual

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Manual 0-2587 33 REPLACEMENT PROCEDURES
NOTE
Failure to properly tighten the seven screws secur-
ing the Input PC Board to the Diode Bridge will
cause damage to the unit.
• The five screws securing the wiring and Input
PC Board to the Diode Bridge must be tight
enough to prevent the wires from moving.
• The two screws securing the Input PC Board to
the Diode Bridge at 'R2' and 'G' must be tight.
D. Input Diode Bridge Assembly Replacement
1. Remove the Left Side Panel per Section 5.04-B.
2. Remove the Input PC Board per paragraph 'C'
above.
3. Remove the two nuts securing the Input Diode
Bridge to the Center Chassis.
4. Remove the Input Diode Bridge Assembly from
the unit.
5. Remove the Thermal Pad from the Center Chassis.
6. Install the replacement Input Diode Bridge Assem-
bly and new Thermal Pad by reversing the above
procedure (see Note).
NOTE
The two nuts removed in Step 3 must be torqued
to 35 in-lbs when reinstalled.
E. Logic PC Board Replacement
1. Remove the Left Side Panel per Section 5.04-B.
2. Carefully remove all cable connections from the
Logic PC Board noting the location of each.
3. Remove the four screws securing the Logic PC
Board to the standoffs.
4. Remove the Work Cable per the following:
a. Remove Right Side Panel per Section 5.04-C.
b. Loosen the Work Cable end at the terminal on
the Output PC Board.
c. Remove the Work Cable end from the Output
PC Board terminal.
d. Remove the tie-wrap holding the Work Cable
to the CD Coil Lead.
e. Carefully pull the Work Cable out through the
Bushing in the Center Chassis.
f. Continue pulling the Work Cable down through
the current sensor mounted on the Logic PC
Board.
5. Install the replacement Logic PC Board by revers-
ing the above procedure.
F. Gate Driver PC Board Replacement
1. Remove the Left Side Panel per Section 5.04-B.
2. Remove the Logic PC Board per paragraph 'E'
above.
3. Carefully remove all cable connections to the Gate
Driver PCB Assembly noting the location of each
per the following chart:
C o n n e ct io n D e scrip t io n o f C a b le
J9
R ib b o n C a b le f ro m L o g ic
PC Bo a rd
J8
R ib b o n C a b le f ro m T o p
F ET / H e a t sin k Asse m b ly
J7
R ib b o n C a b le f ro m Bo t t o m
F ET / H e a t sin k Asse m b ly
4. Remove the four screws securing the Gate Driver
PC Board to the four standoffs.
5. Reinstall the replacement Gate Driver PCB Assem-
bly by reversing the above procedure.
G. FET/Heatsink Assembly Replacement
NOTE
The two FET/Heatsink Assemblies are identical and
are removed in the same manner.
1. Remove the Left Side Panel per Section 5.04-B.
2. Place the unit on its right side.