BENSHAW RediStart EXEXMVRMX3 Series, User Manual

Page: 177 / 222

ATTENTION: The Fiber Optic cables can be damaged if struck or bent sharply. The edge of the printed circuits board should be held
to prevent damage. Special equipment is required for working on the fiber optic portion of the starter. Please contact Benshaw for service
in this area.
8.8.3 SCR Removal
To remove the SCR from heatsink, loosen the two bolts at each end of the clamp body. The SCR has a dowel pin centering it in the heat
sink so the two bolts have to be loosened enough to allow it to clear this pin.
DO NOT loosen the nut on indicator washer. This will
change the clamping pressure of the clamp and the clamp will be rendered defective .
8.8.4 SCR Installation
To install an SCR, use Benshaw approved SCR's. Note that the SCR grade must match the grades of the rest of the SCRs in that phase.
Coat the faces of the SCR's to be installed with a thin layer of electrical joint compound (EJC). Place the SCR's onto the dowel pins
(refer to Figure 52 for proper SCR position). The SCR symbol has a triangle that points to the cathode. Assemble the insulator cups,
washers and bolts as shown in the clamp diagram. Finger tighten the bolts until they are snug, ensuring that the bolts are evenly tightened
and the clamp body is parallel to the heat sink. Tighten each bolt in 1/8 turn increments until the pressure indicator(s) can be turned on
the bolt. This ensures the proper clamping pressure on the SCR.
z
NOTE: For clamps with two washer stacks, it may be necessary to adjust (tighten or loosen) one or both bolts, until both indicators
are even, allowing both washers to spin.
8.8.5 Re-Test SCR's
Once the SCR's have been replaced, perform another SCR Test Procedure.
8.8.6 Re-Assemble Unit
When the SCR readings are correct, re-install the PC boards, RC snubber, and Lexan
ä
or glastic. Make certain that all wiring is done
correctly, and re-install the phase in the unit it was taken from.
167
8 - TROUBLESHOOTING & MAINTENANCE
Figure 52