Lincoln Electric POWER MIG SVM170-A Service Manual page 87

F-47
SCR OUTPUT RECTIFIER REMOVAL AND REPLACEMENT (continued)
FIGURE F.15 — RIGHT HEAT SINK LEAD DISCONNECTION.
SCR
ASSEMBLY
LEAD
5. Remove lead #209S and transformer
lead X4 from the right side heat sink
using a 1/2 in. socket wrench and
1/2 in. open end wrench. See Figure
F.15.
6. Unplug the SCR gate leads G1 and G2
(see wire markers and wiring diagram).
7. Remove the four nuts holding the SCR
assembly to the floor of the machine
using a 3/8 in. nutdriver.
TROUBLESHOOTING AND REPAIR
SCR DIODE
LEAD
LEAD
#320
LEAD
#209S
X4
POWER MIG 255C
LEAD
#320B
8. Clear the leads and carefully remove
the SCR rectifier assembly.
NOTE: When installing the SCR rectifier
assembly, apply a thin coating of Dow
Corning #340 compound to the electrical
connections.
9. Unplug leads 320 and 320B from the
SCR heat sink thermostat on the right
side at the SCR assembly.
10. Reassemble the SCR assembly in the
reverse order.
F-47