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SERVICE INFORMATION
4.3.6 Path Resistance
Verification
Cut
A
Figure 4-5. Triaxial Cable Preparation
I+--- I"-4
(A) Cut off insulation with knife
Cut off outershield.
Insulation over
inner shield
(B) Strip insulation oft inner shield.
(C) Twist inner shield then strip inner conductor.
Twist inner shield and center conductor together,
slip on plastic cover.
(D) Insert wire into hole and rap around body.
(E) Screw
on plastic cover.
The following
paragraphs discuss the equipment,
connec-
tions, and procedure to check path resistance. Should a
particular
pathway
fail the resistance test, the relay (or
relays) for that particular
crosspoint is probably defective.
See the schematic diagram at the end of Section 5 to deter-
mine which relay is defective.
Recommended
Equipment
l
Model 196 DMM
l
7078-TRX-T triax tee adapters (3)
l
Unterminated
3-slot triax cables (4), made from two
7078.TRX-10 triax cables.
l
Banana plugs (4), Keithley
part number BG-10-Z
Connections
Figure 4-6 shows the connections
for the path resistance
tests. The Model 196 is to be connected to the row and col-
umn jacks using prepared triaxlbanana
cables (Figure 4-5,
but with inner shield and center conductor disconnected.)
and 7078-TRX-T triax tee adapters. The special cables can
be made from two 7G7ETRY-10 cables each cut in half, or
four 7G78-TRX-3 cables by cutting one triax connector off
each cable.
4-7
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