Hobart 6T28-600CL Operation And Maintenance Manual page 58

OM-2244 / Operation and Maintenance Manual
DCS-600/ Series 500082 / Solid State Transformer-Rectifiers
f) SCR Diodes
The six SCR diodes mount to the heat sink. If an SCR fails to conduct, it can cause excessive ripple
in the output. If an SCR fails by shorting, the unit can draw excessive input current. SCR replacement
is somewhat complicated, so be sure that a failed SCR is the cause of the problem before replacing.
Refer to Chapter 2-1 for troubleshooting information.
If you plan to replace an SCR, you will need a 903878 Force Indicator Gauge. This gauge, shown in
Figure 1, measures the deflection of the flat spring on top of the SCR as the screws are tightened.
The gauge consists of two metal plates that are free to rotate about a common point where they are
fastened together.

When this gauge is placed on a flat surface so that it makes three-point contact, the sheet metal
plates rotate so that the left edge of the rear plate aligns with the right edge of the front piece at
the calibration notch.

When this gauge is placed on a properly-adjusted SCR spring, the left edge of the rear plate
aligns with the right edge of the front plate at the top notch (marked VE3000/VE2500).
December 15, 2014
Figure 1 Force Indicator Gauge
Chapter 3-1
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