MCi JH-110 Series User Manual page 39

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Be sure that all power plugs are disconnected.
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Page 3-2
Consult your local building code for installation
requirements.
2. Prep re for ny grounding problem by pulling
sep r te ground wires into every conduit.
Use #16 copper wire unless local building codes re ­
quire larger wire. Each ground wire MUST go all the
way back to the System Ground from each location.
DO NOT combine grounds at any other point.
c. Unless the 3rd wire of your ac power system is
unusually noise free, you MUST locate and in ­
stall a " cold water pipe" ground or a "stake "
ground.
d. Do NOT, under any circumstances feed air con ­
ditioners, fan motors, coke machines, flores-
cent lights, etc. from the same power circuit as
the recording equipment. Have a separate
power circuit installed for these types of cir ­
cuits.
a. A relay rack of equipment counts as a single
unit and should be connected to a single
ground wire going to the System Ground. DO
NOT " daisy chain " separate racks.
b. Make all shield connections first leaving
chassis ground wires disconnected until the
following tests have completed.
NOT a good ground and will NOT be a satisfac ­
tory system ground.
With an ohmmeter, test the resistance between
each chassis in the system. You should find a
high resistance between all units. This high
resistance reading is your best assurance
against " ground loops " .
3. Suggested grounding rules for b l nced nd
unb l nced lines.
c. lug in the power cables. If your 3rd wire is a
satisfactory ground, and if ALL units have a 3rd
wire power cable, then your grounding system
» is complete.
NOTE:
Using the 3rd wire grounding system breaks the
first rule of grounding. The 3rd wire usually goes
from one plug to another, so that each piece of
apparatus does not have a separate ground wire
going straight back to the system ground.
Rule 1 — To be effective, the electrostatic shield
must be connected to the same ground
or zero potential reference as the signal
carried within the shield.
Rule 2 — The shield conductor ' s zero potential
reference must be connected to the
same point as the signal ' s ground poten ­
tial point. Any currents in the shield
should drain to the signal ' s ground con ­
nection.
Rule 3 — Every signal line connected to the
system must have its own separate, in ­
dependent shield. When using double
shielded power transformers, every
power line connected to the system
must have its own separate shield.
Remember that every conductor has a finite
resistance. This applies to chassis, ground planes,
and ground buses. If any one point is chosen as a
zero potential reference, no other point can be con ­
sidered to have the same potential. There will always
be some difference in potential between any two
points, regardless of the type of conductor.