3M DELTA Series - Page 12

reason. Rack-mounted units may be installed with 
out their lids. The URM-0001 Universal Rack Mount
kit provides tor air circulation through the units.
FORCED AIR COOLING - DELTA ID UNITS
Delta III units incorporate very densely packed
high-speed electronics on four major printed circuit
boards To provide maximum features, premium
performance and compact size, the electronics were
designed to be space efficient. This required close
component to component and board to board spac 
ing his compact design required supplemental aid
to convection cooling.
The Delta III utilizes an internal miniature cool 
ing fan to augment natural cooling. This fan is
mounted below and to the rear of the center panel.
It blows air upward across the four printed circuit
boards and out through the top. The fan motor
operates from low voltage DC and is variable speed.
Fan speed, and hence, air volume, is controllable
by a trimpot. This is accessible through a small hole
in the rear panel of the machine.
The fan type has been carefully selected to pro 
vide adequate cooling at slow rotor speeds. Typical
fan noise is less than the noise produced by tape
being pulled through a cartridge. The slow fan
speed also prevents abnormal dust or dirt buildup,
as less airborne particulate matter is drawn into the
unit.
Fan speed is factory adjusted to provide ample
cooling for most applications. Should more or less
air flow be required, customers may adjust fan
speed. Units mounted in enclosures, such as fabri 
cated housings , may require increased fan speed.
Units mounted above other heat-producing equip 
ment may also require increased ventilation.
It should be noted that, if the forced air flow is
reduced, internal ambient heat will rise. Delta Series
components are high quality and temperature-rated
higher than the expected heat rise. Lite expectancy
of all components, such as electrolytic capacitors,
may be shortened by reducing the forced air flow.
This is true if the components are operated under
higher than normal heat for extended periods of
time. Therefore, if at all possible, ITC recommends
the use of the Delta III internal forced air system for
optimum performance and maximum longevity of
components.
C. EXTERNAL AUDIO CONNECTIONS
All Delta Series units are shipped with standard
input and output transformers installed. Inputs and
outputs are via 3-pin XLR-type connectors, on the
RIOHT
LIFT
TO
LOAD
REPRODUCER AUDIO OUTPUT CONNECTIONS
RECORDER AUDIO INPUT CONNECTIONS
Figure 2-2
rear panels of respective Delta units. Pin connections
are "universal": Pin 1 is ground. Pins 2 and 3 are the
balanced pair.
Should transformerless operation be desired,
transformer PCB removal is accomplished by turn 
ing the small screwdriver slot in the center of each
XLR connector counterclockwise approximately 1/8
turn, then removing the board from the rear of the
connector. The audio leads on the PCB may be
transferred directly to the XLR socket pins. All Delta
Series units provide balanced active, transformerless
design and may be used in this configuration as
desired.
An appropriate combination of plugs and sock 
ets is provided with each Delta Series unit for con 
necting audio inputs and outputs. Refer to Figures
2-3, 2-4, and 2-5 for location of connectors. Inputs
and outputs are balanced; it is therefore recom 
mended that two-conductor shielded cable be used
for each. Attach the shield only at either the ma 
chine end or the console to prevent any potential
ground loop. Figure 2-2 shows a proper method of
connection for the playback output lines.
It is important to note that the + (plus) and -
(minus) signs are indications of proper phase rela 
tionships only and do not reflect DC voltage poten 
tial. It is necessary to connect the + lines of both
2-2